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Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Under the background of changing global environment and frequent anthropogenic activities, rainfall-runoff relationship has suffered tremendous change in many regions of China, particularly in arid and semi-arid regions. The Jinghe River basin (JRB) in the middle of the Loess Plateau, which is the major base of grain production in Shannxi Province, has experienced significant changes in hydro-climatic variables and the relationship between them during the past decades, causing many water resources problems. In this paper, we focused on analyzing the variation characteristics of rainfall-runoff relationship in JRB, and quantitatively assessing the effects of climate changes and human activities on the runoff reduction. It was of great importance for mastering the evolution of hydrological cycle, water resources planning and management, and water and soil conservation in JRB. The monthly rainfall and runoff data were used in the study and summed annually to investigate the variation characteristics in 1960-2010. To detect the change points of rainfall-runoff relationship, the sliding partial correlation coefficients method was proposed and the change points were further confirmed by the double mass curve method. On the basis of the studies, the relative changes of rainfall, runoff, and rainfall-runoff relationship were analyzed around the change points. Moreover, we also introduced the Archimedean Copula function, from the perspective of probability, to analyze the probability of synchronous-asynchronous encounter of rainfall and runoff in JRB. What caused the variation of rainfall-runoff relationship? Climate change or human activities? To figure out this, the method of slope change ratio of cumulative quantity (SCRCQ) was adopted in this paper. According to these results, we obtained the following conclusions: (i) Annual runoff and rainfall presented wavelike decrease change. Nevertheless, annual runoff declined more greatly than rainfall; especially, in some periods annual rainfall increased, however, runoff decreased. This illustrated that some non-rainfall factors caused the occurrence of phenomenon in JRB; (ii) Change points of rainfall-runoff relationship occurred in 1996 validated by the sliding partial correlation coefficients method and double mass curve method. Meanwhile, we could ascertain the conclusion by the evidence of the process of human activities in JRB, which presented the increasing industrial, agricultural and domestic water consumption and large-scale water conservancy and soil conservation projects since 1990s; (iii) To compare the magnitude of the changes of rainfall, runoff and rainfall-runoff relationship, the hydrological variables series were divided into the periods of 1960-1996 and 1997-2010. Compared to runoff and rainfall in 1960-1996, the annual mean runoff and rainfall in 1997-2010 dropped 43.47% and 6.64%, respectively. The change of monthly rainfall had no significance in different periods. On the contrary, monthly runoff decreased more greatly and the difference was smaller in each month i.e. the runoff distribution for each month was more uniform. The correlation between rainfall and runoff diminished and runoff yield decreased under the same rainfall. When precipitation was above 400 mm, the relative change rate of runoff was above 40% in 1997-2010 compared to that in 1960-1996; (iv) The joint distributions of rainfall and runoff constructed by the Archimedean Copula function were different in 1960-1996 and 1997-2010, and the distributions in the 2 periods were fitting Clayton and Gumbel-Hougaard Copula better, respectively. The probabilities of synchronous-asynchronous encounter of the same rainfall and runoff changed strikingly in different periods. For instance, when rainfall was less than 550 mm and runoff was less than 40 mm, the probability of synchronous-asynchronous encounter was 44% in 1960-1996 and 73% in 1997-2010; (v) In JRB, human activities, i.e. non-rainfall factors, have played a fundamental role in rainfall-runoff relationship change. Further compared with some research results, the irrigation, the construction of reservoirs and the water-and-soil conservation measures in the region should be responsible for the change to a large extent. Compared to the period of 1960-1996, the contribution from human activities in the period of 1997-2010 reached about 81% and climate change was merely around 19% obtained by the method of SCRCQ. The research results can provide theoretical basis for water resource management and water and soil conservation for the administrators. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Fluctuation of animal husbandry system (FAHS) can affect not only the sustainability of farmers' livelihood, but also the stability of regional ecosystem. Characteristics of FAHS and its driving factors in Yanchi County, Ningxia Hui Autonomous Region, which was a typical agro-pastoral zone, were studied and discussed in this paper. According to previous research results and our surveys, total number of sheep was defined as the dependent variable and 10 driving factors were defined as the independent variables, namely, average annual precipitation, average annual temperature, effective irrigated area, grain acreage, gross output of grain, afforestation area, grassland area, vegetation index, agricultural labor force and per capita net income of farmers. Then, the empirical mode decomposition (EMD), which is a powerful method for analyzing the nonlinear and non-stationary time series data, was used to analyze the variability of animal husbandry system and its driving factors. The time series data of total number of sheep and its 10 driving factors from 1954 to 2013 were decomposed into several intrinsic mode functions (IMFs) and a residual trend respectively. Meanwhile, the set pair analysis (SPA) method was used to analyze the contribution of each driving factor to FAHS. Here, 3 IMFs that were decomposed from total number of sheep and the corresponding IMFs that were decomposed from each driving factor were input in the set pair analysis model, and the relationship between FAHS and its driving factors was obtained by this method. The results showed: 1) The total number of sheep increased significantly with an annual fluctuation during the past 60 years and its coefficient of variation was moderate. The total number of sheep had 3 IMFs and its 10 driving factors had 2-5 IMFs. The most of IMFs had the fluctuant periods of 3-4, 7-15, 22-26 and 40-45 years respectively. The IMFs that had the fluctuant period of 22-26 years and the biggest variance contribution were the most important components that were decomposed from the total number of sheep. 2) The fluctuation of the total number of sheep mainly depended on grain acreage, followed by average annual precipitation, and the contribution rate of both driving factors accounted for 75%. The fluctuation of the number of sheep was also weakly affected by average annual temperature, gross output of grain and total output and afforestation area. 3) In these IMFs that were decomposed from total number of sheep, the one that had a longer fluctuation period was affected more seriously by agriculture. In contrast, the one that had a shorter fluctuation period was affected more seriously by climatic factors. Economic and social factors had limited effect on the fluctuations of the total number of sheep. 4) Climatic factors such as average annual precipitation and average annual temperature mainly drove the fluctuation of the total number of sheep. In contrast, grain total output and annual afforestation area had a reverse effect to the total number of sheep. Other 6 factors including effective irrigated area, grain acreage, grassland area, vegetation index, agricultural labor force and per capita net income of farmers had bi-directional effects on the total number of sheep. Based on above analyses, we suggest that the sustainable development for animal husbandry system in Yanchi County is constructing an effective agro-forestry-animal composite husbandry system in this typical agro-pastoral zone. In particular, developing appropriate scale and efficient farmland and feed shrub stands is very important to maintain the stability of animal husbandry system. [ABSTRACT FROM AUTHOR]

The Yellow River flows through an extensive aeolian alluvial plain in Ningxia and Inner Mongolia plateau, which extends from Xiaheyan in Ningxia to Toudaoguai in Inner Mongolia. The Hedong sandy land, the Ulanbuh Desert and the Kubuqi Desert all border on the Yellow River. Frequent strong winds and erodible surfaces cause extreme wind-erosion process in the watershed of Ningxia-Inner Mongolia reach of the Yellow River. A large amount of aeolian sediment flows into the main stream and tributaries of the Yellow River by particle saltation and dune avalanche, which result in the continuous elevation of riverbed. Especially since 1986, the combined operation of Longyangxia Reservoir and Liujiaxia Reservoir has decreased the number and discharge of the flood crest, and lowered the erosiveness of the flow in the upper reach of the Yellow River. In this situation, the siltation of the Ningxia-Inner Mongolia reach of the Yellow River is severer and severer. To resolve the silting problem in this reach, it is urgent to estimate the spatial and temporal variations of wind erosion hazards and the quantities of aeolian sediment fed into the river in this watershed. In this study, the models of IWEMS (integrated wind-erosion modelling system) and RWEQ (revised wind erosion equation) were selected to estimate the wind erosion modulus in this watershed. The observed data in the field in 2011 and 2012 were used to calibrate the models, and the calibration result showed that the simulation accuracies of the 2 models were both satisfactory. Using the calibrated models, the wind erosion moduli in this watershed were obtained. The results showed that the wind erosion moduli in this watershed ranged from 0 to 27 780.6 t/(km2-a) in the period from 1986 to 1995, from 0 to 33 673.1 t/(km2-a) during 1996-2002, from 0 to 37 251.3 t/(km2-a) in the period from 2003 to 2007, and from 0 to 16 111.4 t/(km2-a) in the period from 2008 to 2013, respectively. Since 1986, the wind erosion hazards mainly occurred in the sandy lands such as the Ulanbuh Desert, the Kubuqi Desert and the Hedong sandy land. The wind erosion modulus of the Hedong sandy land gradually dropped from 1986 till now, but the wind erosion modulus of the Ulanbuh Desert was increasingly highlighting in this period, and this desert became to the region with severest wind erosion hazard in the whole watershed. The results also showed that the areas having wind erosion risk in the watershed of the Ningxia-Inner Mongolia reach of the Yellow River were diminishing gradually in these years. The average wind erosion modulus of this watershed was also decreasing, and the fitting regression function between average wind erosion modulus and time showed that the slope was high to -182.81. Based on the estimated wind erosion modulus in watershed of Ningxia-Inner Mongolia reach of the Yellow River, the quantities of aeolian sediment blown into the different reaches of the Yellow River were calculated by aeolian sediment transport equations. The results showed that the Shizuishan- Bayangol reach had the highest value, and the average quantity of aeolian sediment blown into the Yellow River was 9.31 x 106 t/a. The quantity in the Xiaheyan-Qingtongxia reach was lowest, and it was only 7.6 x 105 t/a. Excluding in Shizuishan- Bayangol Reach, in the other reaches, the quantities of aeolian sediment blown into the river did not show the trend of obviously decreasing with time. Through analyzing the relationship between wind erosion modulus and changes of climate and land use, we found the dropping wind erosion modulus in watershed of Ningxia-Inner Mongolia reach of the Yellow River was mainly affected by the climate change. The study results in this paper are not only meaningful for solving the siltation in Ningxia-Inner Mongolia reach of the Yellow River, but also important to the complete the protection systems of wind-blown hazards in this watershed. [ABSTRACT FROM AUTHOR]

Cultivated land is an important indicator of landscape changes driven by human activities. Mapping the spatio-temporal changes of cultivated lands will help us to understand its corresponding environmental and ecological changes in their downstream areas. The Manas drainage basin is the key area of agricultural region in the northern slope of the Tianshan Mountains. However, the drastic farmland reclamation in the last 50 years makes irrigation water increasing rapidly, leading to environmental degradation in the downstream of the Manas River. In this paper, remote sensing and GIS technologies are used to analyze the spatio-temporal characteristics of farmland changes in the Manas drainage basin under the condition of intense soil-water utilization. Firstly, remote sensing images in 1962, 1977, 1989, 2000 and 2010 are applied to map land use changes with the cognition classification software and manual edition. Then the temporal process and spatial pattern of land cover changes are analyzed by geo-statistics and landscape analysis. On the temporal scale, the cultivated land changes and its mutual transition relationships with other land types are analyzed with areal ratio and transition matrix methods; on the spatial scale, GIS spatial analysis tool and landscape class level index are used to describe the characteristics of farmland expansion or shrinking changes in different regions and different land patches. Finally, hydrological data and irrigation construction data are used to explain the impact of climate change and human activities on the farmland landscape. The results show that: (1) The overall land use changes of the Manas drainage basin in the last 50 years are as follows: cultivated land and built-up areas increase continuously, while the unutilized land, wetland and snow/glacier have been decreasing steadily; grassland area is increasing in the former 20 years and then decreasing gradually in the last 30 years; the intensity of land use changes keeps stable after dramatic changes. (2) The overall cultivated land transformations have shifted from outward and inward transformations to single inward transformation; in inward land types, grassland and unutilized land are the main inward land types to farmland, and woodland and wetland take larger percentages in the first 20 years, while less percentages in the later 30 years; in outward land types, built-up land and grassland are the main outward land types, and grassland and unutilized land have larger percentages in the former 20 years due to cultivated land degradation; the total area of inward land types far exceeds than that of the outward land types, and the cultivated land area is steadily increasing in the last 50 years. (3) The focus of cultivated land expansion has shifted from the margins of cities to desert regions, and the newly-increased farmland gradually from the upstream to the downstream; cultivated land expansion firstly begins at the Changji Hutubi and Manas County in the former 20 years, then shifts to Shawan County, the river's surrounding areas and northern deserts; the cultivated landscapes are characterized from discrete and messy pieces into continuous land patches, so the advantage of cultivated landscape is increasing, while the landscape diversity and heterogeneity are decreasing due to land parcel combinations. (4) The increasing precipitation and runoff in the Manas drainage basin provide more water resource for cultivated land reclamation, and reservoir and irrigation channel construction have positive effects on spatial expansion of the cultivated land; when reservoirs and channels are built up, cultivated land will expand correspondingly in a rapid rate in the next decade, and hence the spatio-temporal processes of farmland expansion have high relations with the irrigation facilities. (5) The increasing water resource induced by climate change cannot keep up with the increasing speed of the farmland, and water resource is in the state of over exploitation; measures must be taken to reduce the amount of irrigated water, so as to improve ecological environments in the downstream of the Manas River. [ABSTRACT FROM AUTHOR]

There is an important significance for China's food security to explore the fluctuation characteristics and influence factors of grain output per sown area (hereinafter referred to as grain yield), and then to take corresponding measures to stabilize and improve the grain yield level. In this paper, the time-series yields of grain and main crops (rice, wheat and maize) from 1978 to 2012 in China were decomposed using empirical mode decomposition (EMD) method, and then multi-scale fluctuation characteristics and its main influence factors of grain yield were analyzed. The results showed: 1) the time series of grain yield could be decomposed into two intrinsic mode functions (IMF) and a residual item. The residual item denotes a slow and steady rising trend in grain yield which is dominated by the technological progress. The IMF1 and IMF2 represent a short-term fluctuation in about 4-yr cycle and a medium-term fluctuation in about 9-yr cycle, which respectively reflect the influence of meteorological and policy factors on grain yields according to the analysis of grain production system. The variance contribution rate of the residual item was greatly larger than that of the IMFs, which means the upward trend in grain yield was more pronounced than fluctuations. 2) Fluctuation of trend yield of grain was distinct before and after 1997: fast rise with an average annual growth rate of 2.28% before 1997 and slow rise with an average annual growth rate of only 0.69% after 1997. The change of trend yield was similar between rice and grain, but the former seemed to rise more slowly after 1997. For wheat and maize, the trend yield was still increased obviously although the growing rate had been significantly slowing down after 1997. 3) The IMF2 included 3 complete cycles (1979-1988, 1989-1993, and 1994-2002) and an ongoing cycle (2003 to present) which coincided with adjustment of Chinese agricultural policy. In general, the impact of policy and market factors on fluctuation of grain yield is greater than that of climate factors, but responses of different crops to different policies varied: policies on land, tax, subsidies, incentives and insurance had positive or negative effect on medium-term fluctuation of main crops synchronously, but price policies was not the case for main crops especially for maize. Medium-term fluctuation rate of grain yield was 2.94%, and that of wheat was 3.83%, significantly higher than that of maize (2.38%) and rice (2.18%). It suggested wheat's vulnerability to policies. 4) The short-term fluctuation rate of grain yield was 1.80%, and that of maize, wheat, and rice was 3.38%, 2.55%, and 1.06%, respectively. It indicated that Chinese grain production system had a strong ability to resist against meteorological disaster. The disaster prevention capabilities of different crops was not the same, and maize was more easily affected by meteorological disasters than wheat and rice. 5) Both considering the short-term and medium-term fluctuation rates, rice was the most stable crop in yield. The main problem of rice production was the slow growth of yield trend after 1998, while maize was strongly influenced by meteorological disaster, and fluctuation of wheat was significantly affected by policy cycles. At present, China's agriculture production has entered a new development stage. It is necessary to adjust the agricultural policy in order to adapt to the new situation. The results here can help with decision-making and adjustment of agricultural policies. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The changes of lake water resources record the impacts of climate change and human activities on the regional hydrological processes in the changing environment. Especially for inland areas with less precipitation, timely and accurate information on changes in lake water resources are recorded. Environmental evolution has an important reference value. With China’s largest desert freshwater lake-Hongjiannao Lake as an example, based on the 3S (RS, GIS, and GPS, which are remote sensing, global position system, geographic information system) technology, lake water surface area change was analyzed, which provided important scientific guidance for the restoration, protection and utilization of ecological and economic functions of Hongjiannao Lake. However, due to the different sources of data, the uneven technology, the discontinuous time series and the generally short time series, as well as the different monitoring phases, the result analysis on the change of water area of Hongjiannao Lake is quite different and systematic study and overall analysis of long time series of the entire river basin are lacking. Fifteen periods of both basic and RS data collected for Hongjiannao Lake, such as DRG, DLG, DOM, remote sensing images, and paper maps, were selected for analysis over a recent 60-year period (from 1957 to 2015), together with field annotation data and relevant attributes. All the data and images above have passed the geometric correction of digital elevation model data from Shaanxi Surveying and Mapping Archives and Geological Information Bureau of State Bureau of Surveying and Mapping, which have good quality. Different data can meet the high-precision registration requirements of water body information extraction in the study area. Among them, NDWI (normalized difference water index) with better extraction effect was used to extract water body information, which could restrain the vegetation soil while enhance the water body information. To analyze characteristics in spatio-temporal variations and identify trends of the change in lake water area over the period, we comprehensively utilized RS and GIS techniques and adopted spatial data processes, extracted and interpreted information, constructed a massive database, and conducted integrated management and analysis. We also explored major causes that triggered spatio-temporal variations of lake water area by combining climate change and anthropogenic factors from the same period. Results indicated that in a recent 60-year period, the area covered by water significantly changed in the study area. During 1957-1976, the water area continuously increased from 37.6 to 55.53 km2, and reached the maximum value over the entire record of study with increased amplitude of 47.69%. The growth rates in northern and southeastern areas of the lake were relatively fast, followed by other regions. During 1977-1999, the overall water area was stable, approximately 50 km2. During 2000-2015, water area showed a decreasing trend year by year, from 50.27 to 31.05 km2 with decreased amplitude of 38.23%, and all regions showed this shrinking trend except waters near Qibusu River in 2005, in which the reverse occurred and the water area slightly increased. In general, over the last 60 years, the revolution process of the water area of Hongjiannao Lake could be divided into 3 phases corresponding to the annual variability of water area: expanding period (1957-1976), stabilizing period (1977-1999), and shrinking period (2000-2015), showing an overall shrinking trend. The area of lakes and waters has experienced a dynamic trend of expansion-stabilization-atrophy in the recent 60 years, and has shown a significant atrophy situation since 1999 and a strong signal of ecological and hydrological deterioration, deserving attention. Trends in both warming and drying climate may be the major factors, which affect lake water area variation in both expanding and stabilizing periods, and the superimposition of these trends with anthropogenic effects (i.e. a water conservation project construction in the upper streams, coal mining, pavement construction around the lake, and water consumption for irrigation) may be the essential factor leading to water area variations during the shrinking period. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Climate change, as one of the most important environmental issues, has become an increasing global concern to scientists, policy makers, and the public. Paddy soils are a dominant source of N2O emissions. Agricultural management practices (e.g., water regime, fertilizers management, tillage) have important impacts on N2O emissions due to the changing microenvironment of paddy fields that can affect the processes of soil nitrification and denitrification. This paper summaried current literatures on the influence of these practices on N2O production and emission and their corresponding mechanisms in rice fields. At present, the generation and the pathway of N2O emission from paddy soils are clarified. Nevertheless, the current information on the action of farming management practices on N2O indirect emission is limited. The fertilizer application rate, the various types of fertilizers, and the varying timing and placement of application have a significant effect on the N2O emissions of paddy fields due to the different supplementation of nitrate and ammonium substrate in the processes of nitrification and denitrification. Generally, N2O emissions increase with increasing nitrogen (N) fertilizer rate. Previous studies showed that applying N fertilizer deeper can decrease N2O emissions compared to surface application. Water regime exerts substantial influence on N2O emission through the changes in oxidation and reduction in paddy soil layers during rice cropping. The mid-season aeration and drying-wetting alternation can stimulate N2O generation and emissions from paddy soils. Tillage and residue management practices can also affect nitrification and denitrification due to the change of soil characteristics. However, cultivation patterns do not have significant impacts on N2O emissions from paddy fields in current studies. Further research is needed to study the long-term effects of cultivations on N2O emissions. Most studies showed that N2O emissions decrease by incorporating biochar into paddy soils, but inconsistent results have also been reported. In addition, models (e.g., DNDC, CENTURY) are good options to simulate the effects of alternative agricultural practices on N2O emission from paddy fields and to identify potential strategies for climate change mitigation. In addition, the different effect of farming management practices on N2O emission may be presented based on the difference of many factors (e.g., climate conditions, soil types). An immense challenge to find ways to reduce N2O emission from paddy soils lies ahead for the scientific community and policy makers. Researchable priorities should be: 1) to implement exhaustive research on mechanisms that new agricultural management practices affect N2O generation and its emission pathways; 2) to assess effect of agricultural practices on the direct and indirect N2O emissions from paddy fields and their mechanisms; 3) to make in-depth studies on characteristics of N2O emission in technologies with integration of various farming practices; and 4) to simulate and forecast impacts of agricultural practices on N2O emissions in paddy ecosystems. Integrated farming approaches that exert a crucial role in the reduction of N2O emissions from paddy soils are necessary to be explored to mitigate the consequences of climate change on our planet. [ABSTRACT FROM AUTHOR]

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Transactions of the Chinese Society of Agricultural Engineering is the property of Chinese Society of Agricultural Engineering and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

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Climate change has significant influences on irrigation water demand (IWD) and available irrigation water supply (IWS), which poses grave challenges to farmers and administrators of agriculture and water resources. Due to the complexity and uncertainties from climate, agriculture and water systems, only a few studies have combined these systems together, especially at irrigation district scale. Furthermore, most climate change scenarios (CCS) are continuous time series with uncertainties, meanwhile the corresponding CCS of the typical hydrological years are deficient. Thus it is difficult for the administrators from water sectors and agriculture to make positive responses to climate change. The object of the study was to provide an approach to estimate and assess the influences of climate change on IWS and IWD systems in irrigation district. The study area was a typical northern irrigation district of China, the Baojixia Irrigation District. The model considering IWD, IWS and CCS was developed using system dynamics software i.e. structure thinking experimental learning laboratory with animation (STELLA). There were four function modules: IWDM, IWSM, CCSM and WSDBI. CCSM included the reference crop evapotranspiration (ET0) and the climate factors of future typical hydrological years. Climate factors (i.e. precipitation, air temperature, wind speed, relative humidity and sunshine duration) were predicted using historical data and hydrological frequency calculation principle of inconsistent series. ET0 was calculated by Penman-Monteith equation from the Food and Agriculture Organization of the United Nations (FAO) based on the predicted climate factors. IWDM calculated the irrigation water demands of main crops (wheat, maize, cotton, cole and apple). Crop water requirement was calculated by a simple soil water balance model including effective precipitation, crop coefficient (Kc) and ET0. Net irrigation water demand (NIWD) was the sum of crop water requirements multiplied by their planting areas. IWD was NIWD divided by coefficient of irrigation water effective utilization. IWS was the available irrigation water supply which consisted of ground water and surface water (runoff of Weihe River and reservoirs). The runoff was estimated by historical data and hydrological frequency calculation principle of inconsistent series. The outputs were IWD, IWS and a water supply-demand balance index (WSDBI, i.e. the ratio of IWD and IWS), which were used to evaluate the effects of climate change. The model was verified by historical hydro-meteorological and agriculture data from 2000 to 2010. After validation the predicted CCS and IWS were used as inputs for the simulation of the future irrigation water balance conditions. The conclusions of this research are: 1) The water supply and demand model based on STELLA has a good performance and can be a steady approach for agriculture and water resource simulation. The mean relative errors for IWD and WSDBI are both 3.13%. The mean absolute errors for IWD and WSDBI are 3.9×10-7 m3 and 0.06, respectively. 2) The runoff of Weihe River at Linjiacun station had a significant downward trend at the 0.05 level from 1954 to 2010. It was a jump type of change with its jump range of about -1.43×10-9 m3 occurred in 1989. Compared with the runoff values of different typical hydrological years from 1954 to 2010, the predicted values from 1989 to 2030 were declined by 40%-55% which caused a large reduction of agricultural water supply. The mean temperature and maximum temperature significantly increased meanwhile relative humidity and wind speed significantly decreased at the 0.05 level during 1981-2010. 3) Compared with 2010, the simulation values of IWD in 2030 for wet year (P=25%), normal year (P=50%) and dry year (P=75%) increased by 1.08×10-8, 1.29×10-8 and 1. 21×10-8 m3 respectively, meanwhile the corresponding values of WSDBI increased by 14.46%, 11.70% and 9.06% respectively. The simulation indicated that the IWD and WSDBI increased dramatically under the synthetic action of meteorological factors in future. The supply could not meet the demands except wet years and the situation could be worse over the time, so effective measures should be taken in water resource and agriculture planning and management. This research can provide the reference for assessing the effect of climate change on agricultural water supply and demand in the irrigation district. [ABSTRACT FROM AUTHOR]

Mann-Kendall (MK) trend test is a nonparametric statistical test. When the modified MK (MMK) test was used for serial trend test, it was considered to be stricter than the MK test considering the influence of self-correlation of time series. In this article, the MK method and the MMK method were combined for trend tests of water requirements (ETc) for two main economic crops, i.e., cotton and sugar beet, at 41 stations in Xinjiang over two periods of 1961-1961 and 2015-2099. The influences of serial self-correlation of ETc on trend test results were investigated, and the spatial distribution of trends in ETc of each site and the whole Xinjiang were presented. The results showed that: (1) When the order of self-correlation j was greater than 0, the statistics obtained from the MMK test should be adopted. (2) Over 1961-2010, ETc of both cotton and sugar beet had certain temporal-dependent structures. Over 2015-2099, ETc of cotton had very significant long-range correlation, but ETc of sugar beet hadn't any temporal dependence. (3) Over 1961-2010, which the trends in ETc of cotton at 37 sites decreased, of which the trends in ETc of cotton at 8 sites were significant. Over 2015-2099 for A2 scenario, trends in ETc of cotton at all of the sites in Xinjiang decreased, of which trends in ETc of cotton at 13 sites were significant, while trends in ETc at 28 sites were not significant. For B2 scenarios, only at Luntai the trend in ETc of cotton increased insignificantly, trends in ETc of cotton at the remaining 40 sites decreased. Over 2015-2099 for A2 scenario, trends in ETc of sugar beet at 13 sites increased, of which trends at 3 and 10 sites were significant and insignificant, respectively; trends in ETc of sugar beet at the remaining 28 sites decreased, of which the trends were significantly and insignificant at half of the 28 sites. For B2 scenario, trends in ETc of sugar beet at 9 sites increased. (4) Over 1961-2010, trends in ETc of cotton and sugar beet in the whole Xinjiang decreased significant and insignificant, respectively. Over 2015-2099 for A2 and B2 scenarios, both trends in ETc of cotton decreased significantly; trends in ETc of sugar beet also decreased insignificantly for A2 scenario but significantly for B2 scenario. (5) For both cotton and sugar beet, Sen's slope b were related to the linear slope SL with high coefficients of determination with linear function, which reflected the high consistency of the two variables when describing the trend amplitudes (6) It is necessary to consider the effects of self-correlation for ETc series when using MK test. (7) The synthetic effects of decreases in wind speed and solar radiation as well as the increases in precipitation and relative humidity on the restraining of ETc surpassed the effects of increases in air temperatures in Xinjiang. In conclusion, decreases in the trends of ETc series showed that there were reduced water demands of cotton and sugar beet in the future in Xinjiang, and the risk of drought also reduced. Trend variations in ETc for cotton and sugar beet had important reference value for making the crop irrigation planning and drought disaster prevention under the background of climate change in the arid and semi-arid areas. [ABSTRACT FROM AUTHOR]