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The study of the micro-physical characteristics of spray droplets provides crucial insights into the impact of sprinkler water on soil erosion, leaf impact, and the microclimate of agricultural environments. However, the variability in measurement outcomes across different technologies due to their distinct measurement principles is a significant challenge. This research aims to evaluate and compare the droplet diameter, velocity, application rate, and kinetic energy rate using four distinct measurement technologies: the paper stain method (PS), flour pellet method (FP), laser precipitation monitor (LPM), and two-dimensional video disdrometer (2DVD), alongside a rain gauge (RG) in the context of sprinkler irrigation conditions. The results reveal that: (1) The FP method struggled to capture small droplets under the same spray conditions, while the PS method recorded a maximum droplet diameter exceeding 7 mm. The LPM registered the highest droplet count per unit area and time, notably capturing a significant number of small droplets (< 1 mm). Conversely, the 2DVD provided a more uniform distribution of droplet sizes, with the LPM's mean equivalent droplet diameter (dv) being 0.86 times that of the 2DVD. (2) Although droplet diameters and velocities measured by the 2DVD, LPM, FP, and PS, decreased with increased working pressure, these technologies concurred when assessing low-velocity and small-diameter droplet. (3) The 2DVD's larger sampling area compared to other methods enables the acquisition of more representative droplet characteristics, including their irregular shapes, suggesting its utility in measuring the micro-physical properties of sprayed droplets. (4) Based on the kinetic energy rate measured by the 2DVD under identical conditions, kinetic energy rate calibration factors of 0.88, 1.15, and 1.10 are suggested for the LPM, FP, and PS, respectively. This study provides essential data for calibrating and applying various droplet measurement technologies. [ABSTRACT FROM AUTHOR]

Aim: Assessing water consumption in intercropping systems relative to sole crop systems is important for planting system planning. Methods: This study focused on wheat/maize (Triticum aestivum L./Zea mays L.) relay intercropping to evaluate water use advantage of relay intercropping system based on the same period. Field experiments were conducted from 2014 to 2016, and three cropping patterns were designed: sole wheat, sole maize, wheat/maize intercrops. Method for evaluating water use advantage in intercropping was revised by considering water consumption of sole crops during the fallow period (periods where no plants are grown). Results: Intercropping grain yield was higher than sole cropping yield. Based on the existing method, the intercropping system had 20.4% greater water use than the sole cropping system and the water equivalent ratio (WER) was lower than 1; after revision, intercropping had 7.7% less water use than sole cropping, and the WER was greater than 1. Before revision, intercropped wheat used 3.1% more water than sole wheat, and the intercropped maize used 38.8% more water than sole maize; after revision, intercropped wheat used 24.4% less water than sole wheat, and intercropped maize used 11.0% more water than sole maize. Conclusion: These results indicated that the revised method can be better used to evaluate water use advantage of relay intercropping system. This study implied that wheat/maize intercropping increased both yield and water use based on revised method, and relay intercropping can be a suitable production practice employed in fallow policy, especially in areas with limited water. [ABSTRACT FROM AUTHOR]

The main purpose of this study was to assess the influence of grass planting and jujube branch mulching on soil moisture levels and jujube tree transpiration rates, with the ultimate goal of improving jujube tree production in rain-fed orchards. The study encompassed four treatments: jujube branch mulching (JBM), jujube branch mulching with white clover planting (JBM + WCP), white clover planting (WCP), and clean cultivation (CC). During a two-year experiment, it was observed that the JBM treatment exhibited the highest capacity for moisture conservation. Specifically, it resulted in an average increase of 2.69% (in 2013) and 2.23% (in 2014) in soil moisture content compared with the CC treatment. The application of statistical analysis revealed significant differences (p < 0.05) between JBM and JBM + WCP, as well as highly significant differences (p < 0.01) between JBM and WCP in the year 2013. In 2014, JBM exhibited significant differences (p < 0.01) from both JBM + WCP and WCP. Between April and August, JBM exhibited the highest soil moisture content, followed by CC, with WCP showing the lowest levels. From September to October, JBM retained its status as the treatment with the highest soil moisture content, JBM + WCP ranked second, and CC experienced a decline and recorded the lowest soil moisture content. Under sunny conditions, all treatments showed a broad peak curve in the daily variation of sap flow velocity. In cloudy weather, a multi-peak wave-like curve was observed with similar trends across treatments. Between April and August, the monthly average sap flow velocity of JBM ranked the highest, followed by CC, while WCP showed the lowest velocity. During the period of September to October, JBM maintained its lead in sap flow velocity, while JBM + WCP rose to the second position, and CC's sap flow velocity dropped to the lowest level. JBM and WCP treatments showed significant differences (p < 0.01), and in 2014, JBM also had significant differences (p < 0.05) compared with JBM + WCP. The sap flow velocity was positively correlated with air temperature, vapor pressure deficit, wind velocity, photosynthetically active radiation, and soil temperature. Photosynthetically active radiation was identified as the main driving factor influencing jujube tree transpiration. In conclusion, the findings of this study demonstrate the effectiveness of using pruned jujube branches for coverage in rain-fed jujube orchards. This approach not only conserves mulching materials and diminishes the expenses associated with transporting pruned jujube tree branches away from the jujube orchard but also achieves multiple objectives, including increasing soil moisture, promoting jujube tree transpiration, and enhancing soil water utilization. These results have significant implications for the efficient utilization of rainwater resources in rain-fed jujube orchards and provide valuable insights for practical applications in orchard management. [ABSTRACT FROM AUTHOR]

Evapotranspiration over crop growth period, also referred to as the consumptive water footprint of crop production (WFCP), is an essential component of the hydrological cycle. However, the existing high-resolution consumptive WFCP datasets do not distinguish between soil evaporation and crop transpiration and disregard the impacts of different irrigation practices. This restricts the practical implementation of existing WFCP datasets for precise crop water productivity assessments, agricultural water-saving evaluations, the development of sustainable irrigation techniques, cropping structure optimization, and crop-related interregional virtual water trade analysis. This study establishes a 5-arcmin gridded dataset of monthly green and blue WFCP, evaporation, transpiration, and associated unit WFCP benchmarks for 21 crops grown in China during 2000–2018. The data simulation was based on calibrated AquaCrop modelling under furrow-, sprinkler-, and micro-irrigated as well as rainfed conditions. Data quality was validated by comparing the current results with multiple public datasets and remote sensing products. The improved gridded WFCP dataset is available at 10.5281/zenodo.7756013 (Wang et al., 2023) and effectively compensated for the gaps in the existing datasets through (i) revealing the intensity, structure, and spatiotemporal evolution of both productive and non-productive blue and green water consumption on a monthly scale, and (ii) including crop-by-crop unit WFCP benchmarks according to climatic zones. [ABSTRACT FROM AUTHOR]

The implementation of the "Returning Farmland to Forest" project in the loess hilly region of China has led to the establishment of large-scale economic forests, which have become the dominant industry driving local economic development. However, the region faces challenges such as drought, water shortages, and an uneven distribution of precipitation, which have a severe impact on the growth of economic forests, including jujube trees. Water stress significantly reduces yield and efficiency, posing a threat to the sustainable and healthy development of jujube ecological and economic forests. Therefore, this study aimed to address these issues by implementing straw mulching (SM) and jujube branch mulching (BM) measures in the mountainous jujube economic forests. Through long-term monitoring and statistical analysis, the study investigated the effects of different mulching treatments on soil moisture and soil temperature. The research findings reveal that both SM and BM significantly increased soil moisture in the 0–280 cm soil layer during the jujube growing season (p < 0.05). In both normal precipitation (2014) and drought (2015) years, SM increased average soil moisture content by 5.10% and 4.60%, respectively, compared to the uncovered treatment (CK). SM also had a positive impact on the soil moisture content in each layer of the soil profile. However, BM only increased soil moisture content in the 40–100 cm and 220–280 cm soil layers. Additionally, SM and BM reduced the variation of soil moisture, with SM showing a more significant effect in regulating soil moisture and achieving more stable moisture levels. During the jujube growing seasons in 2014 and 2015, SM and BM decreased soil temperature in the 0–10 cm soil layer. The temperature difference compared to CK decreased with increasing soil depth. SM had an overcooling effect, while BM reduced the temperature before the fruit expansion period and maintained warmth afterward. Both SM and BM also reduced the daily range and variation range of soil temperature, with SM having a more pronounced effect. The temperature of the 0–20 cm soil layer exhibited the strongest correlation with air temperature, and SM showed the weakest response. In conclusion, adopting straw mulching and jujube branch mulching in rain-fed jujube orchards in the loess hilly region not only saves materials and reduces costs but also contributes to water retention and temperature regulation. Straw mulching, in particular, plays a more significant role in moisture retention and temperature regulation and is advantageous for soil management in rain-fed jujube orchards. These research findings provide a scientific basis for optimizing water and heat management in orchards with limited water resources. [ABSTRACT FROM AUTHOR]

Agriculture is the world's largest consumer of water resources, and accurate measurement of crop water footprint (CWF) can provide a scientific basis for evaluating the water use characteristics of agricultural production and guiding water management. The measurement of regional CWF requires large amounts of ground data, and remote sensing provides an effective means to scientifically measure the CWF on a large scale. In this study, we developed an effective means to estimate regional maize CWF based on global evapotranspiration (MOD16 and Global Land Data Assimilation System (GLDAS)‐Noah) products in China. And we also calculated the CWF based on the FAO Penman‐Monteith equation (FAO‐PM) on the site scale in China. We assessed the accuracy of these methods by comparing them against eight eddy‐covariance based flux tower measurements. Links and differences behind the results of the three water footprint calculations were analyzed in terms of the basic principles and characteristics of the calculations. The results showed that the CWF had a similar distribution based on the MOD16 and GLDAS‐Noah, reflecting the influence of regional soil moisture on the CWF. Computational rationale analysis of the three quantitative methods showed that the ETc‐based method from the FAO‐PM model was similar to the MOD16‐ and GLDAS‐Noah‐based CWF in the wetter areas, two remote sensing‐based methods considered the water constraints during soil evaporation and water dissipation during dry and wet canopy conditions, and were closer to reality than the ETc‐based methods in measuring the CWF in arid and semi‐arid regions. Key Points: An effective means based on MOD16 and Global Land Data Assimilation System (GLDAS)‐Noah was developed for simulating regional maize crop water footprint (CWF)The accuracy of the estimated CWF based on FAO‐PM was influenced by the soil moistureThe CWF estimated by MOD16 or GLDAS‐Noah was closer to the reality than that estimated by FAO‐PM, especially in arid and semi‐arid region [ABSTRACT FROM AUTHOR]

The extent and mechanisms by which precipitation extremes affect hydrological processes in the critical zone (CZ) of loess possessing a thick unsaturated zone remains poorly understood. To this end, we here employed a coupled liquid‒vapor‒heat‒airflow STEMMUS (simultaneous transfer of energy, mass, and momentum in unsaturated soil) model to investigate the impact of extreme precipitation, at both event and annual scales, on CZ hydrological processes within a semiarid loess site vegetated by apple trees on China's Loess Plateau. At the event scale, the vapor flux was two orders of magnitude lower than the liquid water flux. However, the thermal vapor flux penetrated to depths of 200 cm, whereas the isothermal liquid water flux only infiltrated to 100 cm during the study period, implying that thermal‐gradient‐driven vapor transfer is an important mechanism for deep‐layer recharge (DLR). At the annual scale, the DLR below 200 cm during extremely wet years was 6.5 times larger than that during extremely dry years. In contrast, extreme changes in climate had only limited impacts on evapotranspiration; the difference between extremely wet and extremely dry years averaged only 35 mm, much less than the difference in precipitation, which averaged 310 mm. However, the extremely dry years showed a higher ratio (0.58) between transpiration and evapotranspiration than did the extremely wet years (0.51). The findings reported here improve our understanding of CZ hydrological processes related to precipitation extremes in semiarid loess regions. Key Points: Thermal‐gradient‐driven vapor transfer is an important mechanism for deep‐layer recharge (DLR) in loessThe DLR below 200 cm during extremely wet years was 6.5 times larger than that during extremely dry yearsExtreme changes in precipitation had only limited impacts on evapotranspiration [ABSTRACT FROM AUTHOR]

Soil water is a major barrier to ecological restoration and sustainable land use in China's Loess Hilly Region. For the restoration of local vegetation and the optimal use of the region's land resources, both theoretically and practically, it is essential to comprehend the soil water regimes under various land use types. The soil water content in the 0–160 cm soil profile of slope cropland, terraced field, jujube orchard, and grassland was continuously measured using EC-5 soil moisture sensors during the growing season (May–October) in the Yuanzegou catchment in the Loess Hilly Region to characterize the changes in soil water in these four typical land use types. The results showed that in both years of normal precipitation and drought, land use patterns varied in seasonal variability, water storage characteristics, and vertical distribution of soil water. In the dry year of 2015, the terraced field effectively held water. During the growing season, the 0–60 cm soil layer's average soil water content was 2.6%, 4.2%, and 1.8% higher than the slope cropland, jujube orchard, and grassland, respectively (p < 0.05), and the 0–160 cm soil layer's water storage was 43.90, 32.08, and 18.69 mm higher than the slope cropland, jujube orchard, and grassland, respectively. The average soil water content of the 0–60 cm soil layer in the jujube orchard was 2.9%, 3.8%, and 4.5% lower than that of slope cropland, terraced field, and grassland, respectively, during the normal precipitation year (2014) (p < 0.05). Only 35.0% of the total soil water storage was effectively stored in the 0–160 cm soil layer of the jujube orchard during the drought year. There was a significant difference in the grey relational grade between the soil water in the top layer (0–20 cm) and the soil water in the middle layer (20–100 cm) under different land use types, with the terraced field having the highest similarity degree of soil water variation trend, followed by grassland, slope cropland, and jujube orchard. Slope croplands in the study region may be converted into terraced fields to enhance the effective use of rainfall resources and encourage the expansion of ecological agriculture. Proper water management practices must be employed to reduce jujube tree water consumption and other wasteful water usage in order to guarantee the jujube orchard's ability to expand sustainably. This would address the issue of the acute water deficit in the rain-fed jujube orchards in the Loess Hilly Region. [ABSTRACT FROM AUTHOR]

Stable water isotopes have been used extensively to study the water use strategy of plants in various ecosystems. In deep vadose zone (DVZ) regions, the rooting depth of trees can reach several meters to tens of meters. However, the existence of roots in deep soils does not necessarily mean the occurrence of root water uptake, which usually occurs at a particular time during the growing season. Therefore, quantifying the contribution of deep-layer soil water (DLSW) in DVZ regions using the natural abundance of stable water isotopes may not be accurate because this method assumes that trees always extract shallow- and deep-layer soil water. We propose a multi-step method for addressing this issue. First, isotopic labeling in deep layers identifies whether trees absorb DLSW and determines the soil layer depths from which trees derive their water source. Next, we calculate water sources based on the natural abundance of stable isotopes in the soil layer determined above to quantify the water use strategy of trees. We also compared the results with the natural abundance of stable water isotopes method. The 11- and 17-year-old apple trees were taken as examples for analyses on China's Loess Plateau. Isotopic labeling showed that the water uptake depth of 11-year-old apple trees reached 300 cm in the blossom and young fruit (BYF) stage and only 100 cm in the fruit swelling (FSW) stage, whereas 17-year-old trees always consumed water from the 0–320 cm soil layer. Overall, apple trees absorbed the most water from deep soils (>140 cm) during the BYF stage, and 17-year-old trees consumed more water in these layers than 11-year-old trees throughout the growing season. In addition, the natural abundance of stable water isotopes method overestimated the contribution of DLSW, especially in the 320–500 cm soil layer. Our findings highlight that determining the occurrence of root water uptake in deep soils helps to quantify the water use strategy of trees in DVZ regions. [ABSTRACT FROM AUTHOR]

Adaptation to future climate change with limited water resources is a major global challenge to sustainable and sufficient crop production. However, the large-scale responses of the crop water footprint and its associated benchmarks under various irrigation regimes to future climate change scenarios remain unclear. The present study quantified the responses of the maize and wheat water footprint (WF) per unit yield (m 3 t -1) as well as the corresponding WF benchmarks under two Representative Concentration Pathway (RCP) scenarios, RCP2.6 and RCP8.5, in the 2030s, 2050s, and 2080s at a 5 arcmin grid level in China. The AquaCrop model with the outputs of six global climate models from Phase 5 of the Coupled Model Intercomparison Project (CMIP5) as its input data was used to simulate the WFs of maize and wheat. The differences among rain-fed wheat and maize and furrow-, micro-, and sprinkler-irrigated wheat and maize were identified. Compared with the baseline year (2013), the maize WF will increase under both RCP2.6 and RCP8.5 (by 17 % and 13 %, respectively) until the 2080s. The wheat WF will increase under RCP2.6 (by 12 % until the 2080s) and decrease (by 12 %) under RCP8.5 until the 2080s, with a higher increase in the wheat yield and a decrease in the wheat WF due to the higher CO 2 concentration in 2080s under RCP8.5. The WF will increase the most for rain-fed crops. Relative to rain-fed crops, micro-irrigation and sprinkler irrigation result in the smallest increases in the WF for maize and wheat, respectively. These water-saving management techniques will mitigate the negative impact of climate change more effectively. The WF benchmarks for maize and wheat in the humid zone (an approximate overall average of 680 m 3 t -1 for maize and 873 m 3 t -1 for wheat at the 20th percentile) are 13 %–32 % higher than those in the arid zone (which experiences an overall average of 601 m 3 t -1 for maize and 753 m 3 t -1 for wheat). The differences in the WF benchmarks among various irrigation regimes are more significant in the arid zone, where they can be as high as 57 % for the 20th percentile: WF benchmarks of 1020 m 3 t -1 for sprinkler-irrigated wheat and 648 m 3 t -1 for micro-irrigated wheat. Nevertheless, the WF benchmarks will not respond to climate changes as dramatically as the WF in the same area, especially in areas with limited agricultural development. The present study demonstrated that the observed different responses to climate change in terms of crop water consumption, water use efficiency, and WF benchmarks under different irrigation regimes cannot be ignored. It also lays the foundation for future investigations into the influences of irrigation methods, RCPs, and crop types on the WF and its benchmarks in response to climate change in all agricultural regions worldwide. [ABSTRACT FROM AUTHOR]

The influence of different mulching measures on soil moisture, soil temperature, and crop growth was investigated during the jujube growing season in rain-fed jujube orchards using micro-plot experiments. The mulching treatments included clean tillage (CT, control treatment), jujube branches mulching (JBM), and white clover planting (WCP). The results revealed that: (1) The average soil moisture content of JBM was greater than that of CT by 3.76% and 2.34%, respectively, during the 2013 and 2014 jujube growth periods, and its soil water deficit was minimal in each soil layer from 0 to 70 cm. WCP had the greatest soil water deficit. The average soil moisture content of the 0–70 cm soil layer in WCP was 3.88% and 5.55% lower than that in CT during the 2013 and 2014 jujube growth seasons, respectively (p < 0.05). (2) JBM had the highest annual average soil moisture content in each soil layer from 0 to 70 cm, followed by CT, while WCP had the lowest. White clover and jujube competed for water in the 20–40 cm soil layer, and JBM had the lowest variation in soil moisture. (3) Mulching with jujube branches and planting white clover could both control the temperature of the 0–25 cm soil layer and narrow the daily temperature range, with JBM being the least affected by air temperature. (4) Jujube's leaf area index and stem diameter increase in JBM were both significantly greater than in CT and WCP. In conclusion, using pruned jujube branches as surface mulch is appropriate for rain-fed jujube orchards because it can preserve soil moisture, regulate soil temperature, and promote jujube growth. [ABSTRACT FROM AUTHOR]

Drought indices are hard to balance in terms of versatility (effectiveness for multiple types of drought), flexibility of timescales, and inclusivity (to what extent they include all physical processes). A lack of consistent source data increases the difficulty of quantifying drought. Here, we present a global monthly drought dataset with a spatial resolution of 0.25 ∘ from 1948 to 2010 based on a multitype and multiscalar drought index, the standardized moisture anomaly index incorporating snow dynamics (SZIsnow), driven by systematic fields from an advanced data assimilation system. The proposed SZIsnow dataset includes different physical water–energy processes, especially snow processes. Our evaluation of the dataset demonstrates its ability to distinguish different types of drought across different timescales. Our assessment also indicates that the dataset adequately captures droughts across different spatial scales. The consideration of snow processes improved the capability of SZIsnow , and the improvement is particularly evident over snow-covered high-latitude (e.g., Arctic region) and high-altitude areas (e.g., Tibetan Plateau). We found that 59.66 % of Earth's land area exhibited a drying trend between 1948 and 2010, and the remaining 40.34 % exhibited a wetting trend. Our results also indicate that the SZIsnow dataset can be employed to capture the large-scale drought events that occurred across the world. Our analysis shows there were 525 drought events with an area larger than 500 000 km2 globally during the study period, of which 68.38 % had a duration longer than 6 months. Therefore, this new drought dataset is well suited to monitoring, assessing, and characterizing drought and can serve as a valuable resource for future drought studies. The database is available at http://doi.org/10.5281/zenodo.5627369 (Wu et al., 2021). [ABSTRACT FROM AUTHOR]

Interspecific interactions and recovery growth play an important role in crop growth, development and ultimately yield in intercropping systems. However, the impact of different water and nitrogen levels on intercropping production, interspecific interactions between intercrops, and the recovery growth of late-maturing crops is still unclear. A two-year field experiment was conducted in Yangling, Shaanxi province, to investigate the dynamics of interspecific interactions, and the effects of interspecific interactions on crop growth and yield. The experiment consisted of three factors, including three cropping systems (wheat/maize intercropping, sole wheat, sole maize), three nitrogen (N) levels and two water applications (supplementary irrigation and rainfed). The results demonstrated that, during the co-growth period, intercropped wheat was more competitive than intercropped maize; so, intercropped wheat showed a yield advantage. Intercropping increased maize yield under irrigated conditions, and this was attributed to the full recovery growth of intercropped maize after wheat harvest. However, rainfed and nil nitrogen aggravated the interspecific competition, and water deficit under maize rows, in turn, limited the recovery growth of intercropped maize, leading to yield reduction. However, compared with sole maize, the yield of intercropped maize decreased, indicating nitrogen deficiency limited the recovery growth of intercropped maize. Among all treatments, the intercropping of medium nitrogen fertilizer with irrigation had the best yield improvement and land use advantages, the total yield of intercropping was 14.8% higher than that of sole cropping, and the land use efficiency increased 16%. These results confirmed that supplementary irrigation and optimal nitrogen application alleviated the interspecific competition, promoted the recovery growth of intercropped maize and improved the yield of wheat/maize intercropping system. [ABSTRACT FROM AUTHOR]

Various land use types have been implemented by the government in the loess hilly region of China to facilitate sustainable land use. Understanding the variability in soil moisture and temperature under various sloping land use types can aid the ecological restoration and sustainable utilization of sloping land resources. The objective of this study was to use approximate entropy (ApEn) to reveal the variations in soil moisture and temperature under different land use types, because ApEn only requires a short data series to obtain robust estimates, with a strong anti-interference ability. An experiment was conducted with four typical land use scenarios (i.e., soybean sloping field, maize terraced field, jujube orchard, and grassland) over two consecutive plant growing seasons (2014 and 2015), and the time series of soil moisture and temperature within different soil depth layers of each land use type were measured in both seasons. The results showed that the changing amplitude, degree of variation, and active layer of soil moisture in the 0–160 cm soil depth layer, as well as the changing amplitude and degree of variation of soil temperature in the 0–100 cm soil layer increased in the jujube orchard over the two growing seasons. The changing amplitude, degree of variation, and active layer of soil moisture all decreased in the maize terraced field, as did the changing amplitude and degree of variation of soil temperature. The ApEn of the soil moisture series was the lowest in the 0–160 cm soil layer in the maize terraced field, and the ApEn of the soil temperature series was the highest in the 0–100 cm layer in the jujube orchard in the two growing seasons. Finally, the jujube orchard soil moisture and temperature change process were more variable, whereas the changes in the maize terraced field were more stable, with a stable soil moisture and temperature. This work highlights the usefulness of ApEn for revealing soil moisture and temperature changes and to guide the management and development of sloping fields. [ABSTRACT FROM AUTHOR]

Growth in water consumption with intensified virtual water (VW) flows from increased production and consumption of both meat and feed crops threatens the sustainability of water resources in water‐scarce countries and export regions. However, a sustainability assessment of both water footprints (WFs) and VW flows related to animal products at a subnational scale is lacking. Here we estimate direct and indirect WFs as well as the inter‐provincial VW flows associated with pork production and consumption in China for the years 2008 and 2017. The contributions of feed crop production and consumption were identified. Both life cycle assessment and WF network frameworks were applied to evaluate the sustainability of blue WF and VW flows. Results show that the national annual consumptive (green‐blue) WF and degradative (gray) WF of pork production increased by 8.7% and 15.8%, respectively. More than 80% of the blue WF in pork production was unsustainable. By 2017, 62% of the unsustainable blue WF and 64% of the water scarcity footprints of pork production in the south resulted from consuming the feed crops from the north. This analysis highlights the importance and provides feasible approaches to uncover remote geographical effects on regional water scarcities from different steps in the value chains of livestock products. Key Points: Over 80% of the blue water footprint of pork production in China is unsustainableOne‐third of pork‐related scarce water is consumed in low‐water‐scarce provincesOne‐fifth of the north‐to‐south virtual water embodied in feed returns by pork [ABSTRACT FROM AUTHOR]

Adaptation to future climate change with limited water resources is a major global challenge to sustainable and sufficient crop production. However, the large-scale responses of crop water footprint and its associated benchmarks under various irrigation techniques to future climate change scenarios remain unclear. The present study quantified the responses of maize and wheat water footprint per unit yield (WFP, m³ t-1) and corresponding WFP benchmarks under two representative concentration pathways (RCPs) in the 2030s, 2050s, and 2080s at a 5-arc minute grid level in the case for China. The differences among rain-fed and furrow-, micro-, and sprinkler-irrigated wheat and maize were identified. Compared with the baseline year (2013), maize WFP will increase under both RCP2.6 and RCP8.5, by 17 % and 13 %, respectively, until the 2080s. Wheat WFP will increase under RCP2.6 (by 12 % until the 2080s), while decrease by 12 % under RCP8.5 until the 2080s. WFP will increase the most for rain-fed crops. Relative to rain-fed crops, micro irrigation and sprinkler irrigation result in the smallest increases in WFP for maize and wheat, respectively. These water-saving managements will more effectively mitigate the negative impact of climate change. Furthermore, the spatial distributions of WFP benchmarks will not change as dramatically as those of WFP. The present study demonstrated that the visible different responses to climate change in terms of crop water consumption, water use efficiency, and WFP benchmarks under different irrigation techniques must be addressed and monitored. It also lays the foundation for future investigations into the influences of irrigation methods, RCPs, and crop types on WFP and its benchmarks in response to climate change in all agricultural regions worldwide. [ABSTRACT FROM AUTHOR]

Deep soil (>2 m) moisture is relatively stable water that supports tree growth and water management in the loess hilly–gully area of China. Characterizing the spatial variation of deep soil moisture is important for water management in apple orchards. Using a space‐for‐time substitution approach, we analysed the spatial variation of soil moisture content (θ) in 0–8 m soil profiles in a dry year (2015, precipitation: 392 mm) in rainfed apple (Malus pumila Mill.) orchards of various ages (mainly established in 2009, 2006, 2003, 1997 and 1994). The soil moisture surveys revealed: (a) four soil layers according to soil moisture distribution characteristics at 0–8.0 m depth: shallow rapidly changing layer (0–0.6 m), rainfall redistribution layer (0.6–2.0 m), transition layer (2.0–4.0 m) and stable layer (4.0–8.0 m); (b) the most critical zone for water consumption is the 0.6–2.0 m soil layer, with the lowest θ in the orchards, while water in the 4.0–8.0 m soil layer remained stable; and (c) significant (p <.01) positive correlations between θs in the 0.6–2.0 m, 2.0–4.0 m and 4.0–8.0 m layers. In addition, the θs showed a significant (p <.01) negative relationship with orchard age in the deep soil layers (>2 m), and especially in the 0.6–2.0 m soil layer. Therefore, effective water management through various water regulation measures at the 0.6–2.0 m soil layer is essential for the sustainable development of apple orchards and reducing drought stress on the Loess Plateau and, potentially, other semi‐arid orchards. [ABSTRACT FROM AUTHOR]

The implementation of large-scale vegetation restoration over the Chinese Loess Plateau has achieved clear improvements in vegetation fraction, as evidenced by large areas of slopes and plains being restored to grassland or forest. However, such large-scale vegetation restoration has altered land-atmosphere exchanges of water and energy, as the land surface characteristics have changed. These variations could affect regional climate, especially local precipitation. Quantitatively evaluating this feedback is an important scientific question in hydrometeorology. This study constructs a coupled land-atmosphere model incorporating vegetation dynamics, and analyzes the spatio-temporal changes of different land use types and land surface parameters over the Loess Plateau. By considering the impacts of vegetation restoration on the water-energy cycle and on land-atmosphere interactions, we quantified the feedback effect of vegetation restoration on local precipitation across the Loess Plateau, and discussed the important underlying processes. To achieve a quantitative evaluation, we designed two simulation experiments, comprising a real scenario with vegetation restoration and a hypothetical scenario without vegetation restoration. These enabled a comparison and analysis of the net impact of vegetation restoration on local precipitation. The results show that vegetation restoration had a positive effect on local precipitation over the Loess Plateau. Observations show that precipitation on the Loess Plateau increased significantly, at a rate of 7.84 mm yr−2, from 2000 to 2015. The simulations show that the contribution of large-scale vegetation restoration to the precipitation increase was about 37.4%, while external atmospheric circulation changes beyond the Loess Plateau contributed the other 62.6%. The average annual precipitation under the vegetation restoration scenario over the Loess Plateau was 12.4% higher than that under the scenario without vegetation restoration. The above research results have important theoretical and practical significance for the ecological protection and optimal development of the Loess Plateau, as well as the sustainable management of vegetation restoration. [ABSTRACT FROM AUTHOR]

A core goal of sustainable agricultural water resources management is to implement a lower water footprint (WF), i.e. higher water productivity, and to maximize economic benefits in crop production. However, previous studies mostly focused on crop water productivity from a single physical perspective. Little attention is paid to synergies and trade-offs between water consumption and economic value creation of crop production. Distinguishing between blue and green water composition, grain and cash crops, and irrigation and rainfed production modes in China, this study calculates the production-based WF (PWF) and derives the economic value-based WF (EWF) of 14 major crops in 31 provinces for each year over 2001–2016. The synergy evaluation index (SI) of PWF and EWF is proposed to reveal the synergies and trade-offs of crop water productivity and its economic value from the WF perspective. Results show that both the PWF and EWF of most considered crops in China decreased with the increase in crop yield and prices. The high (low) values of both the PWF and EWF of grain crops tended to cluster obviously in space and there existed a huge difference between blue and green water in economic value creation. Moreover, the SI revealed a serious incongruity between PWFs and EWFs both in grain and cash crops. Negative SI values occurred mostly in north-west China for grain crops, and overall more often and with lower values for cash crops. Unreasonable regional planting structure and crop prices resulted in this incongruity, suggesting the need to promote regional coordinated development to adjust the planting structure according to local conditions and to regulate crop prices rationally. [ABSTRACT FROM AUTHOR]

Background and aims: Understanding the variability in water availability in agroforestry systems in rain-fed orchards is vital for optimizing orchard management in semiarid areas. However, few studies have examined the soil capacity of water stock and supply in these systems over multiple years. We aim at (i) characterizing several soil physical properties related to water availability and inter-annual dynamics of soil water content and (ii) exploring their response to meteorological conditions and root distribution. Methods: Jujube (Ziziphus jujuba Mill.) intercropped with the fodder species canola (Brassica napus L.) (JFCS), jujube intercropped with daylily (Hemerocallis fulva L.) (JDLS), and a jujube orchard with clean tillage (JCS) were established on the Loess Plateau, China. Soil physical properties (including soil bulk density, soil hydraulic conductivity, soil field capacity, and soil porosity), soil water content and fine root data were collected over the period 2014–2017. Results: Compared to JCS-Tree, the field capacity was significantly increased both in the JFCS-Tree and JDLS-Tree treatments, while soil capillary porosity increased significantly only in the JFCS-Tree. Compared to JCS-Inter-row, the JFCS-Inter-row and JDLS-Inter-row exhibited significantly decreased soil bulk density, and increased field capacity, saturated hydraulic conductivity, and improved soil porosity, but the non-capillary porosity in the JDLS-Inter-row treatment were not significantly modified. Compare to JCS-Tree treatment, the soil water at 0–60 cm significantly increased under JFCS-Tree and JDLS-Tree in four years. However, due to the deeper fine root distribution for both tree and crop under JDLS-Inter-row, the soil water content at 60–180 cm in JDLS-Inter-row significantly decreased more than JFCS-Inter-row and JCS-Inter-row. Conclusions: The introduced crop modified the soil physical properties and soil water content, indirectly under trees and directly between inter-rows through the role of fine roots, thereby changing the orchard environment in semiarid areas. Agroforests can generally improve water condition at shallow soil layers compared to monocultural plantations, although such an effect may be accompanied with lower water stock at deeper soil layers in inter-rows, depending on crop species chosen. [ABSTRACT FROM AUTHOR]

China's food security has met standards set by the United Nations Food and Agriculture Organization. However, this development is based on excessive resource input and sacrificing the environment. There are few studies on how to evaluate food production systems with a sustainability framework. In order to guarantee the food security in Northwest China, and realize the sustainable development of agricultural production, this study was carried out. On the basis of comprehensive analysis of new problems faced, including water resources, cultivated land resources and ecological security, several indicators such as water resources development and utilization rate, cultivated land pressure index, cultivated land quality index, N and P emissions and emission intensity are proposed to comprehensively evaluate the sustainability of grain production in Northwest China and put forward countermeasures to realize regional sustainable development. The results show that the water resources are already at a high‐stress level as the development and utilization rate of water resources is 42.7% in 2015. Industrial and domestic water continues to squeeze agricultural water use (annual average reduction of 0.1%). The amount of per capita cultivated land in 2015 has decreased by 9.7% compared to 2000. The quality index of cultivated land is as low as 0.22. A series of ecological problems caused by agricultural production have intensified the ecological crisis in the Northwest, which in turn will further affect food security. Suggestions to address these issues include improving agricultural water use efficiency, strengthening the measures of arable land conservation, improving fertilizer utilization efficiency and reducing plastic‐film mulch residues. [ABSTRACT FROM AUTHOR]

This study is intended to simulate and better understand mean and extreme precipitation over the Loess Plateau (LP) in China using the Weather Research and Forecasting (WRF) model. We performed a long-term (1980–2011) simulation with the WRF model at a 10 km horizontal resolution, forced by the ERA-Interim reanalysis. A series of sensitivity experiments were conducted to investigate the influence of resolution and physical parameterization schemes on the simulation ability of the WRF model over the LP. The region has a dominant semi-arid climate and is adversely affected by extreme precipitation. Results show that the WRF model produced better simulations at a 10 km resolution for the LP with complex terrain than it did at coarser resolutions. WRF simulations for precipitation over the LP were most sensitive to cumulus schemes, moderately sensitive to planetary boundary layer schemes, and less sensitive to microphysics schemes. The WRF model not only adequately captured the spatial distribution of precipitation in the LP but also reproduced its magnitude and variability at different time scales. Moreover, the WRF model captured 73% of the observed extreme precipitation events with an intensity of more than 12 mm day− 1, which cause substantial soil erosion in the LP. Although it was unable to capture 27% of the observed events, the WRF model reasonably reproduced ERA-Interim extreme precipitation and its dynamic processes. These analyses strongly suggest that the biased extreme precipitation generated with the WRF model most likely resulted from inaccurate ERA-Interim forcing data. This study provides a better understanding of extreme precipitation simulations as well as insight into predictions of soil erosion in the LP. [ABSTRACT FROM AUTHOR]

Widespread land degradation has stimulated the implementation of a large‐scale ecological restoration programme in China's Loess Plateau—the Grain‐for‐Green Programme (GFGP). This programme has substantially increased vegetation cover and served to control soil erosion, but threatened regional food supply due to widespread cropland conversion. Consequently, a strategy balancing green and grain land uses is required. Here, we establish a dominance index of ecosystem services by quantifying the economic value of four key ecosystem services (net primary productivity, soil conservation, water yield, and food production), by combining spatially explicit datasets and census data. Using the dominance index, we identify the optimal areas to target for GFGP in the Loess Plateau. The identified areas (target areas) were the transition zone from low to high value of ecosystem services (ESV). These areas exhibited low grain productivity in addition to having the highest potential for soil conservation. Compared with other regions of the Loess Plateau, the loss of grain production due to cropland conversion in these target areas could decrease by 42%, whereas ESV could increase by 33%. Therefore, despite the fact that over the past 15 years (2000–2014) in these target areas more cropland was converted into ecological use (i.e. forest/grassland), there is still a need to strengthen ecological restoration in this region in the future. This study proposed a strategy for balancing green and grain from a spatial perspective, which could potentially solve land degradation issues and the tradeoff between ecosystem services in a more beneficial and targeted way. [ABSTRACT FROM AUTHOR]

An introduction to the journal is presented that focuses on the significance of root traits in genetics and breeding, adaptation to water and nutrient deficits, root trait variation and plasticity in response to agronomic practices and interaction with soil microbiome.

Background and Aims: Understanding the characteristics of root system is important for optimization of intercropping systems and increased utilization efficiency of limited resources. However, few studies have examined root development and water uptake in wheat/maize intercropping system under different water conditions. Methods: A two-year field experiment of sole wheat, sole maize, and intercropped wheat/maize was carried out under rainfed conditions and supplementary irrigation. Roots of wheat and maize were sampled seven times over the two growing seasons (2014–2015 and 2015–2016) using auger and monolith methods. Results: Root growth and distribution were promoted in intercropped wheat, while in intercropped maize roots both were suppressed. The maximum lateral extension distance of intercropped wheat under rainfed conditions varied from 40 to 50 cm during the co-growth period, which was significantly (p < 0.05) greater than that under supplementary irrigation conditions (25–30 cm), allowing intercropped wheat to access soil water in the area between the wheat and maize strips. Meanwhile, after wheat harvest, intercropped maize roots grown under supplementary irrigation showed growth recovery mainly in a horizontal direction with maximum lateral distance of 50 cm. Conclusions: Intercropping boosted the capacity of wheat roots but suppressed root growth in maize, and rainfed conditions encouraged the lateral distribution of intercropped wheat roots. [ABSTRACT FROM AUTHOR]

Agricultural sectors are facing various environmental threats, such as land degradation and water resource depletion. Agricultural water use and cropping patterns are closely linked to each other, with both related to the regional climate. This study evaluated the impacts of future climate and agricultural land‐use changes on agricultural water consumption in the Hetao Irrigation District (HID), China. The results show that owing to an increase in temperature and a decrease in precipitation, the future climate in the research area will become warmer and dryer, which will increase the water demand of crops. Future climate in the HID will lead to a 10.5% increase in total irrigation water demand under a scenario of high greenhouse gas emissions and a 6.9% increase under a scenario of low greenhouse gas emissions. Results of the grey prediction modeling indicate that the amount of water allocated to the agricultural sector will decrease, which will make it difficult to meet crop irrigation demands. The results of the gray model also show that the cropping pattern in the HID will vary over time, and the proportion of the area of cash crops will increase by 5.3% during the next decade. Regional agricultural water use can be reduced by adjusting the cropping pattern under irrigation water limitations. Meanwhile, the saved water can be used for soil desalination in cultivated land in the HID. Consequently, adjusting the cropping pattern is a nature‐based solution by which to address climate change and guarantee the sustainable use of regional water and land resources. [ABSTRACT FROM AUTHOR]

The accurate estimation of profile soil moisture is usually difficult due to the associated costs, strong spatiotemporal variability, and nonlinear relationship between surface and profile moisture. Here, we used data sets from the Soil and Climate Analysis Network to test how reliably observation operators developed based on the cumulative distribution function matching method can predict profile soil moisture from surface measurements. We first analysed how temporal resolution (hourly, daily, and weekly) and data length (half year, 1 year, 2 years, and 4 years) affected the performance of observation operators. The results showed that temporal resolution had a negligible influence on the performance of observation operators. However, a leave‐one‐year‐out cross‐validation showed that data length affected the performance of observation operators; a 2‐year interval was identified as the most suitable duration due to its low uncertainty in prediction accuracy. The robustness of the observation operators was then tested in three primary climates (humid continental, humid subtropical, and semiarid) of the continental United States, with the exponential filter employed as an independent method. The results indicated that observation operators reliably predicted profile soil moisture for most of the tested stations and performed almost equally well as the exponential filter method. The presented results verified the feasibility of using the cumulative distribution function matching method to predict profile soil moisture from surface measurements. [ABSTRACT FROM AUTHOR]

There have been significant recent advances in understanding the ecohydrology of deep soil. However, the links between root development and water usage in the deep critical zone remains poorly understood. To clarify the interaction between water use and root development in deep soil, we investigated soil water and root profiles beyond maximum rooting depth in five apple orchards planted on farmland with stand ages of 8, 11, 15, 18, and 22 years in a subhumid region on the Chinese Loess Plateau. Apple trees rooted progressively deeper for water with increasing stand age and reached 23.2 ± 0.8 m for the 22‐year‐old trees. Soil water deficit in deep soil increased with tree age and was 1,530 ± 43 mm for a stand age of 22 years. Measured root deepening rate was far great than the reported pore water velocity, which demonstrated that trees are mining resident old water. The deficits are not replenished during the life‐span of the orchard, showing a one‐way mining of the critical zone water. The one‐way root water mining may have changed the fine root profile from an exponential pattern in the 8‐year‐old orchard to a relative uniform distribution in older orchards. Our findings enhance our understanding of water‐root interaction in deep soil and reveal the unintended consequences of critical zone dewatering during the lifespan of apple trees. [ABSTRACT FROM AUTHOR]

Vegetative filter strips (VFSs) are a common type of off‐site method used to enhance the sustainability of catchment systems by promoting desirable soil and landscape functions. The transport of water run‐off and sediment to downstream reaches can be restricted by VFSs in the flow path. The adoption of VFSs is increasing because they have been demonstrated to be effective for trapping run‐off and sediment. Thus, an optimized design procedure for developing VFSs is required. To further understand the roles of both vegetation type and geometric size in the design of VFSs, global sensitivity analysis (GSA) within the Vegetative Filter Strip Modeling System was conducted using a traditional elementary effect test and a novel density‐based method called PAWN. The analysis involved both a uniform and a concentrated flow scenario. The GSA outcomes indicated that the inputs related to vegetation type were vital for the VFS design, especially in terms of the run‐off reduction function of the VFS, irrespective of the scenario that was used. The vertical saturated hydraulic conductivity was the main input responsible for the influence of vegetation type. The inputs related to vegetation type had limited influences on the sediment trapping performance of the VFS, which was shown to be mainly controlled by the length of the VFS. The role of vegetation type in the design of VFSs must be fully considered, especially in cases in which VFSs are established primarily for flood control or run‐off reduction purposes. [ABSTRACT FROM AUTHOR]

Sprinkler irrigation application uniformity is an important indicator for sprinkler irrigation system design, which can be expressed by the Christiansen uniformity coefficient (CU). The calculated accuracy of CU is closely related with catch‐can spacing and grid size. In theory, the smaller the catch‐can spacing and grid size are, the more accurate the calculation of CU is. However, smaller catch‐can spacing needs more labor in water distribution measurement, and smaller grid size needs more computer runtime to calculate CU. In order to recommend the proper catch‐can spacing and grid size, an experiment is carried out to obtain four different water distribution patterns, and data characteristics for water distribution with various catch‐can spacing and the effect of catch‐can spacing and grid size on CU are studied in the paper. The results show that CU is overestimated for the larger catch‐can spacing, especially when the distribution of water for the pattern is non‐uniformity. CU changes very little within a certain catch‐can spacing and grid size for all the four patterns. Considering the accuracy of CU calculation, labor cost, and the computational runtime, the recommended catch‐can spacing is 1.96 m for pattern I, 0.92 m for patterns III and IV, and the recommended grid size in the calculation of CU is 1.25, 1.0, and 0.5 m for patterns I, III, and IV, respectively. [ABSTRACT FROM AUTHOR]

Emitter clogging has a direct impact on the performance and service life of a drip irrigation system. A study of labyrinth emitter clogging was conducted to determine the effects of pulsating versus constant pressure on average emitter flow rate ( $$\overline{q}$$ ), the Christiansen uniformity coefficient (Cu), and the location of clogged emitters. Under constant pressure, emitters in this study began to be clogged after the 8th irrigation, whereby 15 emitters eventually became clogged; the average emitter flow rate decreased to 75% of the original emitter flow rate ( $${{q}_{0}}$$ ) after the 15th irrigation, and Cu decreased rapidly by 68.2%. For pulsating pressure, emitters began to be clogged after the 14th irrigation, only 5 emitters became clogged, and $$\overline{q}$$ only decreased to 85.3% of $${{q}_{0}}$$ , and Cu declined by only 22.6%. These results demonstrate that the anti-clogging performance of emitters with pulsating pressure is better than with constant pressure. Emitter clogging at a constant pressure generally occurred at the inlet and front of labyrinth channels, mainly due to deposition of sediment particles. Emitter clogging with pulsating pressure is due to other impurities (e.g., debris of Teflon tape) besides sediment particles plugging the labyrinth channel. Pulsating pressure is recommended for use in drip irrigation to prevent emitter clogging. [ABSTRACT FROM AUTHOR]

Planting economic trees is one of the primary parts of the large-scale ecological rehabilitation project (known as 'Grain for Green' project) initiated in 1999 on the Loess Plateau of China. Knowledge of soil water dynamics and fine roots patterns is critical to water management for orchards in this region. Here we investigated the distribution of root-zone soil water variation and fine roots with a range of stand ages (2, 6, 10 and 15 years) in a rain-fed jujube ( Ziziphus jujuba) plantation on the Loess Plateau. Soil water in the 0- to 3-m depth was monitored using portable Time Domain Reflectometry, and root samples were taken with a hand auger ( Φ = 9 cm). The results showed soil water storage in the 0- to 0·6-m soil layers in all stands increased remarkably following apparent rainfall events. However, there was no clear change in soil water storage below 0·6 m throughout the growing season. Generally, fine root length density increased with the increase of stand age, which were unevenly distributed in the vertical and horizontal directions around the tree trunks in young stands (2 and 6 years), and the fine roots were uniformly distributed radically from the tree trunk in mature stands (10 and 15 years). Additionally, a high-density zone of fine roots was observed in the middle of the inter-row in mature stands, and the specific length of fine roots in young stands was higher than observed in mature stands. The results presented here would be helpful to water management in the rain-fed jujube plantations on Loess Plateau and potentially for other semi-arid orchards. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

ABSTRACT The trends of major climatic variables at annual and seasonal scales over the past 51 years (1960-2010) in arid areas of northwest ( NW) China are investigated using the Mann-Kendall test. From the results it is clear that the majority of the trends (more than 94%) showed significant increasing tendency in three annual temperature indices, including the mean temperature ( Tmean), the mean minimum temperature ( Tmin) and mean maximum temperature ( Tmax). For Tmax, however, the significant increase was mainly the result of more significant increases in autumn. The annual and seasonal precipitation ( P) series showed positive as well as negative trends. Stations with negative trends were mainly located in the Loess plateau for all of the investigated spring, autumn and annual time series. The precipitation trends in the winter exhibited consistently positive values, but most of these trends were not significant. The annual and seasonal wind speed ( U) decreased significantly at the majority of the stations. More stations showed significant decreasing trends in spring than those in other seasons. The variations in the annual and seasonal relative humidity ( Rh) series were relatively stable over the region. Most time series showed non-significant changes, although both positive and negative trends were detected. The results confirmed a particularly strong recent climate change in arid areas of NW China, especially in terms of temperature and wind speed. [ABSTRACT FROM AUTHOR]

Land degradation is recognized as a major environmental problem in rainfed fruit orchards on the Chinese Loess Plateau. Six treatments were used to investigate surface runoff and soil moisture by means of simulated rainfall experiments: (i) a control (clean cultivation) (CC); (ii) strip cock's foot ( Dactylis glomerata L.) cover (SCF); (iii) strip crown vetch ( Coronilla varia L.) cover (SCV); (iv) strip bird's foot trefoil ( Lotus corniculatus L.) cover (SBF); (v) strip white clover ( Trifolium repens L.) cover (SWC); and (vi) complete white clover cover (WCC). The time to runoff was significantly longer under WCC than under other treatments ( p < 0·05). The total runoff volume and sediment yield were significantly greater under CC than under the vegetation cover treatments ( p < 0·05). The mean infiltration rate under WCC and CC was the largest and lowest and differed significantly from that under other treatments ( p < 0·05). The change of soil water storage was the largest under WCC and the least under CC. The soil moisture was significantly greater under SCF than under other treatments ( p < 0·05). Treatment SCF seemed to be the best groundcover for rainfed sloping jujube orchards on the Chinese Loess Plateau. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Based on a 28-year in situ experiment, this paper investigated the impacts of organic and inorganic fertiliser applications on soil organic carbon (SOC) content and soil hydraulic properties of the silt loam (Eumorthic Anthrosols) soils derived from loess soil in the Guanzhong Plain of China. There were two crop (winter wheat and summer maize) rotations with conventional tillage. The treatments included control without fertiliser application, organic manure application (M), chemical fertiliser application (NP), and the application of organic manure with chemical fertiliser (MNP). The results showed that the 28-year organic manure applications (M and MNP) significantly ( p < 0·05) increased SOC content at surface layer (0-10 cm), but the effect of chemical fertilisers alone on SOC was not significant. Organic manure treatments (M and MNP) apparently improved soil hydraulic properties. Compared with control, field capacity and total porosity significantly ( p < 0·05) increased while soil bulk density significantly ( p < 0·05) decreased for organic manure applications. The M and MNP treatments increased soil water retentions by 3·2-10·8%, which was dependent of suction tensions. However, the NP treatment had no significantly impact on soil water retention compared with control. Neither organic nor inorganic fertiliser applications significantly changed saturated hydraulic conductivity. However, a clear difference was observed for unsaturated hydraulic conductivity between the M and the control at 0-5 cm. Overall, long-term applications of organic manuring increased SOC content and amended soil hydraulic properties. However, the effects of chemical fertilisers on these soil properties were limited. Copyright © 2015 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Soil erosion is a key factor affecting sustainable agriculture on Chinese Loess Plateau. A 2-year study was conducted on jujube trees in a controlled study to compare effects of clean cultivation (CC) with jujube branch mulch (WJBM), strip white clover cover (SWC), strip shallow tillage (ST), jujube branch mulch under tree canopy + strip white clover cover (JBM + SWC) and jujube branch mulch under tree canopy + strip shallow tillage (JMB + ST). The study was on sloping soil (26·7%) in mesocosms (2·0 m × 0·8 m × 0·8 m) using a rainfall simulator. Runoff volume and sediment yield were significantly larger under CC than other treatments ( p < 0·05), and were least under WJBM. Water infiltration under CC was significantly less than other treatments ( p < 0·05), while it was the largest under WJBM. The available nitrogen ( AN) and available phosphorus ( AP) runoff loss under CC were significantly larger than others ( p < 0·05), and least under WJBM. No differences in soil AN, AP and water-soluble organic carbon ( WSOC) concentrations were detected among all treatments. The soil AN and WSOC concentration under all treatments decreased during the growing season and slightly increased during fallow, while AP concentrations fluctuated but decreased slowly. The WJBM was the best management in this sloping jujube orchard study. Copyright © 2014 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Water use efficiency assessment is one of the core research items in water-saving agriculture. The water footprint (WF) of crop production is a comprehensive indicator reflecting water consumption types, quantities and water use efficiency during crop growth period. Based on the theory of water footprint, this study quantified and evaluated the regional differences of water footprint of wheat at the regional scale in Mainland China. Meanwhile, in order to find the dominant factors causing the regional differences of water footprint of wheat, correlation and path coefficient analysis were used to identify the relationship between water footprint of wheat and its impact factors. The results showed that there were obvious regional differences of water footprint of wheat in Mainland China. The water footprint of wheat was relatively low in the eastern part of Northeast China, most of Huang-huai-hai region, parts of the Lower-Middle Reaches of the Yangtze River and Sichuan province, which was less than 1 m3/kg; while the high values of water footprint of wheat were mainly distributed in Northwest China, the northwest of Inner Mongolia, the south of Lower-Middle Reaches of the Yangtze River and the south of Southwest China, which were more than 1.8 m3/kg. From the perspective of water type, the blue water footprint accounted for 49.02%, while the green water footprint accounted for 50.98% among the total WF of wheat. The green water proportion in wheat water footprint increased gradually from northern regions to southern regions. For instance, the proportion of green water footprint was 18.62% in Beijing, while it was more than 80% in most of southern regions. The regional distinction of green proportion in water footprint was in accordance with the precipitation on distribution. The region with abundant precipitation usually has a high proportion of green water in crop water footprint. There were 9 related factors selected for the attribution analysis: average temperature, relative humidity, growing season precipitation, solar radiation, wind speed, fertilizer consumption, pesticides consumption, agricultural machinery and irrigation share. The statistical analysis revealed that the regional variability of wheat water footprint, besides the crop varieties, was mainly caused by the regional disparities of agricultural production level, such as agricultural inputs and irrigation condition. On the other hands, the solar radiation and precipitation were the major climatic influencing factors causing the regional difference of water footprint of wheat. The indirect path coefficient of water footprint of wheat and its impact factors showed that solar radiation had indirect effects on water footprint through temperature, and precipitation mainly through relative humidity. Meanwhile, the fertilizer consumption, pesticides consumption, agricultural machinery power, irrigation had indirect effect on water footprint of wheat through each other influencing factors. The total influence coefficient analysis showed that the chemical fertilizer consumption, pesticides consumption, agricultural machinery and irrigation were the dominant factors that had an effect on water footprint of wheat. The results can provide information for plan-making of agricultural water management schedule. [ABSTRACT FROM AUTHOR]

BACKGROUND: Analysis of cropping patterns is a prerequisite for their optimisation, and evaluation of virtualwater flows could shed new light on water resources management. This study is intended to explore the effects of cropping pattern changes between 1960 and 2008 on virtual water flows related to crops transfer in the Hetao irrigation district, China. RESULTS: (1) The sownarea of crops increased at an average rate of 3.57×10³ ha year-1 while the proportion of sown grain crops decreased from 92.83% in the 1960s to 50.22% in the 2000s. (2) Virtual water content decreased during the study period while net virtual water exports increased since the 1980s. (3) Assuming that the cropping pattern was constant and was equal to the average 1960s value, accumulated net virtual water export in 1980-2008 would have been 4.76×109 m³ greater than that in the actual cropping pattern scenario. CONCLUSION: Cropping pattern changes in the Hetao irrigation district could not only be seen as resulting fromthe pursuit for higher economic returns, but also as a feedback response to limited water resources. A systematic framework is still needed for future cropping pattern planning by taking food security, continued agricultural expansion and other constraints into consideration. [ABSTRACT FROM AUTHOR]

Recognizing the need for a comprehensive review of the tools and metrics for the quantification and assessment of water footprints, and allowing for the opportunity for open discussion on the challenges and future of water footprinting methodology, an international symposium on water footprint was organized. The Water Footprint Symposium was held in December 2013 at the University of Leeds, UK. In particular, four areas were highlighted for discussion: water footprint and agriculture, quantification of water footprint, industrial water footprint, and from theory to practice. Discussion was organized to focus on the 'prioritization of water footprint research & applications to practical sectors'. The concept of water footprinting has helped to better communicate water management and assessment among different research and user communities. Significant research progress has been made in the relations between water footprint and agriculture, quantification of water footprint, industrial water footprint, and the transition from theory to practice. Future water footprint research needs to further enhance assessment accuracy, improve sustainability assessment methodology, develop databases, address uncertainties, and prioritize application by government and in practical sectors. More information on the symposium can be found on the water@leeds website: . [ABSTRACT FROM AUTHOR]

The image obtaining angle and scope for the fixed image acquisition device is limited for obtaining an image of the desired crop; with the high cost of running the system, a vehicle-mounted mobile multipoint access method needs to move the car as the carrier, and affects the image acquisition system automation level. In order to obtain a crop image in an enlarged acquisition scope, a crop image acquisition system was developed that the image acquisition device can move on a fixed truss. The system has five parts: an image acquisition device, rotation and pitching motion, vertical movement, horizontal movement, a remote control, and database management. The image color of crop growth information is at least 24 bit, and a resolution up to 640 ×480 pixels. A high-definition network camera was used as the image acquisition device. A comprehensive intelligent control Pan Tilt Zoom (PTZ) was selected as the rotation and pitching motion, in order to expand the scope of monitoring, to increase the space rotation and to add pitching motion. The image acquisition device was installed on the intelligent control PTZ to achieve 360° rotation and pitching movement. A helix four bar mechanism was designed for the vertical movement and the PTZ was fixed on it to achieve vertical movement for the camera. A sliding block guide mechanism was developed and the helix four bar mechanism was installed on it to achieve horizontal movement for the camera. Vertical movement and horizontal movement were driven by two stepper motors. Both stepper motors were checked, to ensure the system dynamics. In addition, the control software for the crop image remote acquisition system was developed. For the vertical movement and horizontal movement, the steering, speed, and step size control of stepper motor were realized by an intelligent stepper motor controller with a port of RJ45. For the rotation and pitching motion, the 360° rotation, the four directions moving of PTZ and pitch motion control of PTZ were realized, by an intelligent control PTZ. For the image acquisition device, the functions of the camera such as the lens, focus, action of the camera, adjustment of aperture and video recording, were realized. The crop image database and the remote management system were also established with the functions such as image storage, download and upload statistical inquiries and so on. The system in a greenhouse was carried out in five months, with the system running stably, with a clear crop image and video information. Response of the control system time was less than 1 s, with the precision reaching 96.2%, the control accuracy reaching 96.2%, the crop image transmission response time was less than 2.5 s, which satisfied the use requirement. The image database management system is mainly used for image storage, download and upload, statistical query, etc. This crop image acquisition system provides a platform to diagnose the water and fertilize remotely by the obtained image in different parts for all plants within the monitoring area. [ABSTRACT FROM AUTHOR]

China faces the dual challenge of grain production pressure and water scarcity. It is significant to reduce water footprint of grain product ( WFGP, m/t) in irrigated farmland. The focus of grain production and agricultural water use, and the precondition is to determine the WFGP and its composition. This paper estimates the WFGP in irrigated farmland of 31 provinces (including municipalities, autonomous regions) a by collecting actual data of 443 typical irrigation districts in 1998, 2005 and 2010, and analyses its temporal and spatial variation in irrigated farmland of China. The result shows that the WFGP in each province decreases with time except in Jiangxi and Hunan, and the average value of all provinces reduced from 1494 m/t in 1998 to 1243 m/t in 2010. The WFGP decreases faster in more developed municipal cities and major grain production provinces. The annual average WFGP in irrigated farmland is 1339 m/t and the blue and green water account for 63.5 % and 36.5 % of the total, respectively. The WFGP and its composition are significantly different between provinces. Generally, provinces distributed inside and beyond Huang-Huai-Hai Plain, have a higher water productivity, lower WFGP and blue water footprint of grain product, while most provinces located in northwest, northeast, southeast and south China have a higher WFGP and lower proportion of green water in the WFGP as a whole. Portion of the blue water footprint ( BWFGP) is not consumed for crop evapotranspiration ( BWFGP) but conveyance loss (B WFGP). The national averaged BWFGP decreases with time and but still remains up to 466 m/t in 2010, making up 34.8 % of the WFGP. In order to safeguard grain security and ease the water resource pressure, the Chinese government should increase investment and apply advanced technology for developing water-saving agriculture, improve the efficiency of water use and further reduce the WFGP. Considering also the contribution of grain output and the relatively high WFGP, the government should give priority to developing water-saving agriculture in the Northeast of China. [ABSTRACT FROM AUTHOR]

Soil moisture variability and controls are little known in large gullies of the Loess Plateau which represent complex topography with steep slopes. This study analyzed spatial-temporal variability of soil moisture at the 0-20, 20-40, 40-60, and 60-80 cm depths in a large gully of the Loess Plateau based on root-zone soil moisture measurements for 3 years (2009-2011). The result showed that mean soil moisture, standard deviation (SD), and coefficient of variation, were highly dependent on depth; the highest mean value was observed at the 20-40 cm depth, while the lowest one was at the 0-20 cm depth. The SD increased with mean soil moisture for various depths as soil moisture was relatively wet; however, a transition that SD decreased with mean soil moisture occurred when soil moisture was relatively dry. Positive correlations exist between moisture contents over different depths, and that the relationships of the neighboring layers are relatively high with R from 0.70 to 0.76. Correlation analysis, principle component analysis, and stepwise multiple regression analysis showed that soil particle size distribution and topography (slope and elevation) were the main environmental factors controlling soil moisture variability in the large gully. [ABSTRACT FROM AUTHOR]

ABSTRACT Two distinct approaches can be employed in the classification and divisions of wet/dry climate. The first is the rule-driven strategy with predefined threshold values representing climate division boundaries, which is usually performed by Aridity Index ( AI). The second is an automated method in a data-driven fashion, avoiding the direct specification of classification rules while utilizing some forms of cluster analysis. However, various methods for climate classifications raise issues on their applicability and quality. Therefore, evaluation and comparative studies are needed to handle such issues first, in order to analyze their performance and second, to better understand climate characteristics in a region. This article makes a comprehensive analysis and comparison among five classification methods, including four rule-driven methods based on different categories [Penman-Monteith (PM), Thornthwaite, Holdridge, Sahin's method] and one data-driven method (factor-cluster analysis). With the meteorological data for long-term period (1981-2010), the wet/dry climate divisions were performed for 191 meteorological stations in Northwest China ( NW). The results indicated that the overall climate regimes were in agreement for five classifications, but boundaries of wet/dry climate divisions in a data-driven fashion showed a better consistency with topographic features. PM classifications displayed more arid climate types in NW, while the Thornthwaite approach showed an underestimate in arid environments. All wet/dry climate types corresponding to Holdridge and Sahin's classifications were represented in NW, but Holdridge classification is more easily affected by topography and elevation. Complete comparisons among rule-driven methods are difficult to conduct due to different class definitions and low coincident classes. Class definition of climate types for different rule-driven classifications thus needs further investigation. This article highlights the importance of acknowledging the limitations and advantages of different classification systems as well as the dry and wet climate conditions in NW in hope to provide a reference for a similar geographical region. [ABSTRACT FROM AUTHOR]

Accurate estimation of reference evapotranspiration (ET) becomes imperative for better managing the more and more limited agricultural water resources. This study examined the feasibility of developing generalized artificial neural network (GANN) models for ET estimation using weather data from four locations representing different climatic patterns. Four GANN models with different combinations of meteorological variables as inputs were examined. The developed models were directly tested with climatic data from other four distinct stations. The results showed that the GANN model with five inputs, maximum temperature, minimum temperature, relative humidity, solar radiation, and wind speed, performed the best, while that considering only maximum temperature and minimum temperature resulted in the lowest accuracy. All the GANN models exhibited high accuracy under both arid and humid conditions. The GANN models were also compared with multivariate linear regression (MLR) models and three conventional methods: Hargreaves, Priestley-Taylor, and Penman equations. All the GANN models showed better performance than the corresponding MLR models. Although Hargreaves and Priestley-Taylor equations performed slightly better than the GANN models considering the same inputs at arid and semiarid stations, they showed worse performance at humid and subhumid stations, and GANN models performed better on average. The results of this study demonstrated the great generalization potential of artificial neural techniques in ET modeling. [ABSTRACT FROM AUTHOR]

The assessment of agricultural production efficiency of Hetao irrigation district of Inner Mongolia, an important agricultural production area of China, is of great significance in guaranteeing national food security. Much attention has been paid to blue water (surface and groundwater), while the use of green water (rainwater insofar as it does not become run-off) is rarely included in the agricultural production analysis. Compared to blue water, the cost of green water is less, but its environmental impact is concerned . Consequently, this paper analyzed agricultural productive efficiency of five counties in the Hetao irrigation district during 2000-2008 using data envelopment analysis (DEA) by considering blue water, green water, and other indicators. First, the technology efficiency, pure technology efficiency, and scale efficiency were analyzed combining CCR-I and BCC-I models and then some suggestions about how to adjust the amount of input resources were provided for ineffective decision making units (DMU). Results show that: among the 45 DMUs, there were 24 DMUs that were DEA-effective. The values of technology efficiency, pure technology efficiency, and scale efficiency of five counties during the period of 2005-2008 were greater than those during the period of 2000-2004. The differences of technology efficiency in different counties were not significant and the value for Qianqi (0.878) was smaller than the other four counties, which were larger than 0.9. The agricultural productivity efficiency of Qianqi was mainly influenced by production scale and it was the application of technology for Hanghou and Wuyuan. In order to be DEA-effective, the inputs of 21 DMUs should be decreased and the decreasing proportions were 16.66% (blue water), 22.23% (green water), 19.46% (irrigation areas with salinization problem), 20.66% (irrigation areas without salinization problem) and 23.82% (agricultural population). The use of different resources was inefficient and would have an adverse effect on the development of the irrigation district. To some extent, the redundancy of water and land resources in agricultural production may be related to the characteristics of green water. The rainfall in the Hetao irrigation district was uneven both temporally and spatially. Local farmers would increase the use of blue water and land resources when they were not sure about the amount of green water that the crops could use to achieve a better harvest. As a result, the use efficiency of blue water and land resources would decrease when the grain production was lower than the expectation value, which was mainly caused by the litter rainfall. The use efficiency of green water would decrease when the expectation green water was larger than actual value. In the future, the rational distribution of labor among agricultural production and other industries would be helpful in achieving a more effective agricultural production pattern for the Hetao irrigation district. Besides, the improvements of irrigation frustration and land resources management were also needed for the Hetao irrigation district. hift of cropping pattern to crops with lower irrigation water input and higher output would also be suggested considering the difficulty in decreasing the redundancy for green water. This study could provide some suggestions for the efficient agricultural production in the Hetao irrigation district and the improvement of the agricultural production system in other irrigation districts. [ABSTRACT FROM AUTHOR]

By using the Variable Infiltration Capacity model with Palmer Drought Severity Index (VIC-PDSI) model and Standardized Precipitation Index (SPI), spatiotemporal trends of climate variation during the main growing seasons for plants of Loess Plateau between 1971 and 2010 were detected and characterized. The VIC-PDSI model is established by combining the VIC model with PDSI. The simulation results and the grids system of VIC were applied to substitute for the two-layer bucket-type model to do the hydrological accounting, which could improve the physical mechanism of PDSI and expand its application range. Our results suggest that the climate of the study area has experienced a drying and warming trend during the past four decades. Apart from some individual years and regions, there was a perpetuation of water deficit over the Plateau both in spring and summer. The drought frequency increased from southeast to northwest in spring, while the drought frequency decreased from southeast to northwest in summer. The climate in the southern part of the Loess Plateau, accounting for 23.3% of the study region, showed a significant drying and warming trend in spring over the past four decades. The climate variability detected by VIC-PDSI model shows good agreement with that monitored by SPI. Since a large part of the study region frequently suffered from water shortage during the main growing seasons for plants, people living in such drought-prone areas should take measures to prevent the negative effects on agricultural production, reforestation, and regional food security caused by drought. Copyright © 2013 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

BACKGROUND The effects of vegetation cover ( VC) on runoff and sediment yield were investigated from rainfall simulation experiments in the Loess Plateau of China. Five VCs from 0% to 80% and three different rainfall intensities ( I2.0, 1.5, 0.75) were implemented. RESULTS The results indicated that runoff and sediment yields in slopes were significantly affected by I and VC, and when the VC amounted to 40% there occurred obvious benefits of runoff and sediment reductions and then amplitude decreased with the increase of VC. The runoff reduction benefits at I1.5 and I0.75 were much greater than that at I2.0, while the sediment reduction benefits had no significant difference among different rainfall intensities. At I2.0, the natural grassland slopes with high VC exhibited the characteristics of high runoff but low sediment production. There existed a power function relationship between cumulative runoff and sediment yield. The increase in cumulative sediment yield was less than the increase in cumulative runoff with increasing VC, and the sediment reduction benefit was greater than runoff reduction on natural grassland slopes. CONCLUSION The ratio of runoff reduction to sediment reduction can be used as a comprehensive index for assessing the benefits of runoff and sediment reduction in natural grassland. © 2013 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Rainwater harvesting could increase the resilience of ecosystems on the Loess Plateau and thus ensure the sustainability of livelihoods that depend on them. As such, it is a key component of strategies for adapting to global climate change. In this study, we used a new method to quantify the rainwater harvesting potential (RWHP) across the whole Loess Plateau and to characterize its spatial and temporal variation over the last four decades on the basis of the variable infiltration capacity model. It was found that that the mean RWHP of the study region was 731.10 × 108 m3, and the average water layer thickness was 114.34 mm. There is considerable scope for rainwater harvesting across the Loess Plateau as a whole, to the extent that it could potentially provide enough water to implement the 'Grain for Green' Project. The annual average RWHP decreased slightly from 1971 to 2010, and Hurst exponent analysis indicated that this trend will exhibit long-term persistence. The annual RWHP was highest in the southeast of the Loess Plateau and lowest in the northwest. Areas with high RWHP values tended to be clustered around the middle reach of the Yellow River. For most areas, there was no significant change between 1971 and 2010. Those areas for which there was a significant decrease in RWHP were primarily located around the upper-middle reaches of the Weihe River, the upper reach of Jinghe River, the eastern Guanzhong Plain, the Qinhe River watershed and the area around Dongsheng. Quantitative assessments of RWHP are likely to be useful for guiding the development and use of innovative rainwater harvesting technologies around the world and could help to relieve the problems caused by water shortages on the Loess Plateau while simultaneously eliminate the major cause of soil erosion. Copyright © 2012 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]