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Transparent calcium oxide (CaO) ceramic was successfully fabricated by pressureless vacuum sintering technique with 0.5 at% YF 3 as the sintering additive. In consideration of the hydrolysis of CaO, the precursor powders were calcined at 600 °C. Within the sintering temperature range of 1150–1450 °C, the effect of YF 3 additive on the phase structure, relative density, transmittance, and microstructure of CaO ceramics was studied. Benefiting from the assisted liquid-phase sintering mechanism and vacancy diffusion mechanism of YF 3 , full-dense (3.35 g/cm3) YF 3 -doped CaO transparent ceramic was fabricated at 1350 °C with high thermal conductivity of 15.42 W/(m·K). The in-line transmittance attained 47.10% at the wavelength of 1200 nm. Moreover, the hydrolysis resistance was extremely enhanced due to the pore-free structure. Compared to the CaO ceramic with low relative density of 78.66%, the weight gain of full-dense CaO ceramic greatly decreased from 22% to 1.2% within 35 days. [ABSTRACT FROM AUTHOR]

Abstract Biochar application is proposed having a potential of inhibiting greenhouse gases emissions from paddy fields, which is considered to be a main source of atmospheric greenhouse gases. However, the impacts of biochar on greenhouse gases from paddy field have not been investigated under controlled irrigation (CI). Field experiments were conducted during 2016–2017 to determine the effect of biochar application combined with controlled irrigation on rice yield and methane (CH 4) and nitrous oxide (N 2 O) emission from paddy fields in the Taihu Lake Region of China. Four treatments (0 t ha−1 biochar +CI, 20 t ha−1 biochar +CI, 40 t ha−1 biochar +CI, and 40 t ha−1 biochar + flooding irrigation (FI), named CA, CB, CC and FC, respectively) were designed in this study. The results showed that the effect of biochar application on greenhouse gases emissions from paddy fields under controlled irrigation had significant interannual differences. In the first season, CC decreased the global warming potential(GWP) of CH 4 and N 2 O emission, and the CB increased the GWP of CH 4 and N 2 O emission compared to CA, but these differences were not significant. For the second season, CB and CC decreased the GWP of CH 4 and N 2 O emission by 35.7% and 21.5% significantly compared to CA due to the significant mitigation of CH 4 and N 2 O emission. Biochar application significantly increased CH 4 emission and decreased N 2 O emission from paddy fields under flooding irrigation compared to controlled irrigation (CC), which led to the FC's GWP was 1.70 and 5.47 times higher than CC's in the first and second season. In addition, biochar application increased soil organic carbon, dissolved organic carbon and total nitrogen contents of paddy fields under controlled irrigation. And CB and CC increased rice yield by 16.7% and 24.3% and irrigation water productivity by 26.1% and 30.8% compared with CA (mean of two seasons). These results suggest that 20 and 40 t ha−1 biochar can be utilized under controlled irrigation not only for mitigation of CH 4 and N 2 O emission but also to increase rice yield, soil fertility and irrigation water productivity. Therefore, the combination of biochar amendment and controlled irrigation might be a good option for mitigating greenhouse gases emission and realizing the sustainable utilization of soil and water resources of paddy fields in the Taihu Lake Region of China. Highlights • 20 t ha−1 biochar application significantly increased soil DOC, TN, NH 4 +-N and decreased NO 3 −-N concentrations. • Biochar amendments increased rice yield and irrigation water productivity (mean of two rice seasons). • Biochar application combined with controlled irrigation reduced the mean GWP of two rice seasons. [ABSTRACT FROM AUTHOR]

Straw return (SR) and rice water-saving irrigation (WSI) affect the greenhouse gas emission of paddy fields. However, studies on CO2 exchange between paddy fields and the atmosphere with joint regulation of SR and WSI are few. We conducted a two-year field experiment to investigate the effects of SR on soil respiration and net ecosystem exchange of CO2 (NEE) in paddy fields under controlled irrigation (CI), which is a typical WSI technique. The rice yields, irrigation water use efficiency, seasonal variations in soil respiration, NEE, and soil organic carbon content were measured. Compared with the control (flooding irrigation and traditional chemical fertilizer), a significant increase in rice yield and irrigation water use efficiency in the paddy fields under CI and SR joint management (CS) was observed. CS increased the soil respiration rate during most of the rice growth stage and increased the net CO2 absorption rate before approximately 80 days after transplanting; afterward, the pattern reversed. Total CO2 emissions through soil respiration in CS paddy fields increased by 43.7% and 182% compared with the control in 2014 and 2015, respectively. However, CS also caused an increase in the total net CO2 absorption by 18.1% and 30.1% in these two years, respectively. The acceleration in the consumption and decomposition of soil organic carbon induced by frequent alternate wet–dry cycles of the CI paddy fields increased the soil respiration and decreased the net CO2 absorption. SR promoted soil respiration but also improved rice growth, increasing the net CO2 absorption. The soil organic carbon content of the CS paddy fields after harvesting increased by 23.2% compared with that before transplanting. The present study concluded that joint regulation of WSI and SR is an effective measure for maintaining yield, increasing irrigation water use efficiency, mitigating CO2 emission, and promoting paddy soil fertility. [ABSTRACT FROM AUTHOR]

Improper management practices lead to the reduction of phosphorus availability by rice and an increase in the risk of phosphorus release to the environment in paddy fields. This study aims at exploring the effects of biochar with the applicated rate of 0, 20, 40 t ha−1 under controlled or flooding irrigation on utilization efficiency of phosphorus fertilizer and phosphorus leaching loss from fields by observing the dynamics of phosphorus in paddy fields throughout the rice growing period. The results indicated that biochar application lessened the TP and DRP leaching loss by 6.77–17.62% and 6.22–10.28% respectively. It was also found that biochar improved the phosphorus efficiency of rice by 5.33–10.33%and reduced the soil phosphorus surplus by 3.45–6.66% for the increased soil Olsen-P concentration and soil solution dissolved reactive P concentration. In comparison with flooding irrigation, controlled irrigation apparently decreased P leaching loss by 34.64–55.15% by controlling the downward migration of phosphorus in soil solution. Although biochar addition in the field increased production cost, it was proved increasing net economic benefit by 2558–4655 yuan ha−1 y−1, which attributes to the increased rice yield in biochar applicated treatment. In order to improve phosphorus efficiency of rice and reduce the risk of phosphorus release to the environment, a combination of biochar and water-saving irrigation applied in rice fields can provide cleaner production of rice with a promising option, thus bringing both environmental and economic benefits. [Display omitted] • Dynamics of P in soil and soil solution were monitored in biochar applicated paddy field under water-saving irrigation. • Biochar application and water saving irrigation reduced P leaching loss from paddy field. • Biochar application increased P efficiency in water-saving paddy field. • Biochar drove the increase of available P content. [ABSTRACT FROM AUTHOR]

[Display omitted] • DNDC-BC was established on the water balance principle and two-pool biochar model. • DNDC-BC can model GHG, SOC and rice yield of paddy under CI and biochar. • DNDC-BC performed better in simulating GHG and soil moisture than the original one. • Coupling CI and biochar decrease CH 4 and N 2 O emissions, boost SOC and rice yield. • CH 4 and N 2 O emissions from CI paddy are most sensitive to rainfall and irrigation. Simulating the impacts of biochar and controlled irrigation (CI, a water-saving irrigation technology without surface ponding of water) combination on greenhouse gas (GHG) emissions from paddy fields is crucial, however, the original DNDC model is not capable of capturing these management impacts on emissions. In this study, we have created a new modelling approach called DNDC-Biochar-Controlled Irrigation (DNDC-BC) by adding two modules to the original DNDC: the water balance principle, and the two-pool biochar model. The performance of the DNDC-BC was tested and validated using a two-year field experiment, designed with two irrigation treatments (flood irrigation (FI), and CI) and three biochar application rates (0, 20, and 40 t ha−1), carried in the Lake Taihu region, China. Results revealed that the DNDC-BC model performed satisfactorily in simulating impacts of biochar-CI combination on emissions of CH 4 , N 2 O, SOC, and grain yield. The corresponding R2 values of DNDC-BC increased by 22.63%-35.66%, 43.00%-71.26%, 1.06%-60.87% and 15.38%-34.78% compared with those of the original model. Sensitivity analysis for the DNDC-BC showed that CH 4 emissions were most sensitive to rainfall and irrigation; N 2 O emissions were sensitive to rainfall, irrigation and N fertilizer application rate, and SOC was sensitive to biochar application rates. Our results suggest that the combination of biochar- and CI can save water resources and mitigate GHG emissions without detrimental impacts on rice yield. The DNDC-BC can be used to estimate the long-term impacts of biochar-CI combination on GHG emission, crop productivity and climate change. [ABSTRACT FROM AUTHOR]

Yield and rice quality indicators of crops are a direct reflection of the rational irrigation and fertilizer strategy. However, the effects of controlled irrigation (CI) combined with the split application of fertilization managements (straw returning, organic fertilizer, and conventional fertilizer) on rice quality are not clear in southeast China. This study aims at exploring the effects of three fertilization managements applied under CI or flooding irrigation on rice yield, quality, enzyme activity, and soluble sugar content including 43 indicators, to determine the optimal comprehensive evaluation model, management, and representative indexes. The results showed that compared with CF (CI + conventional fertilizer), CS (CI + straw returning) significantly increased yield (27.65%), irrigation water use efficiency (6.20%), chalky grain rate (9.67%), chalkiness (1.83%), protein content (4.29%), and amylose content (0.33%), indicating that CS improved yield and milling quality but decreased cooking and appearance quality. This was mainly because CS promoted the activities of alpha-amylase, ADPG (ADP-glucose pyrophosphorylase), and GBSS (granule-bound starch synthase) and reduced the soluble sugar content in rice. Grey relational degree analysis (GRD), the entropy method (ETM), and TOPSIS (the technique for order preference by similarity to an ideal solution) were used to comprehensively evaluate the rice quality and determined that CS treatments could synergistically improve yield and rice quality. The five indexes (adhesive strength, HPV, ADPG, soluble sugar (leaf), yield) and TOPSIS model can be used as the best indexes and model to evaluate the rice quality. These results could provide scientific management and evaluate practices for high-yield and high-quality rice cultivation, which may be promising for a cleaner production strategy. [ABSTRACT FROM AUTHOR]

Accurate water level prediction is the premise of farmland waterlogging prediction. A simple water level prediction model (FDPRE) based on four machine learning (ML) algorithms and weather forecasts were developed. The model can not only predict two key driving factors of waterlogging, rainfall and node water level but also estimate disaster losses. The results showed that the random forest and Multiple perception model (R2 ranged from 0.7180 to 0.9803 and 0.5717 to 0.9965) performed best. In the case of flooding lasting for one day, the economic loss of waterlogging under the 100 mm rainfall scenario (23.53 million dollars) was much higher than that under the 50 mm rainfall (12.69 million dollars). Under the two rainfall scenarios, the yield reduction rate in the lower reaches of the Sihu basin was higher than that in the upper reaches. The method of coupling ML and weather forecasts can well predict farmland waterlogging. • FDPRE, a simple water level prediction model, was developed. • Farmland flood disaster was predicted on machine learning and weather forecast. • Random forest performed best among the four machine learning models at most sites. • The economic loss of waterlogging under 100 mm rainfall was much higher than 50 mm. [ABSTRACT FROM AUTHOR]

Irrigation mode is an important factor in regulating CH 4 and N 2 O emissions from croplands. However, there are no studies on the effects of irrigation mode practiced during the rice season on the annual integrative global warming potential (GWP) of CH 4 and N 2 O in the rice–winter wheat rotation systems. Thus, a field experiment was designed to study the effects of controlled irrigation (CI) during the rice season on the annual integrative GWP of CH 4 and N 2 O emissions from the rice–winter wheat rotation systems, with traditional irrigation (TI) as the control. A notable trade-off relationship between CH 4 and N 2 O emissions was observed in the rice–wheat rotation systems under both CI and TI of rice. CI during the rice season had obvious subsequent effects on CH 4 and N 2 O emissions from the following winter wheat season. Over the whole annual cycle, CI significantly reduced the cumulative CH 4 emission (13.27 kg ha −1 ) by 80.6% than that from the TI fields ( p < 0.001), but did not cause a significant difference on the cumulative N 2 O emission ( p > 0.05). The integrative GWP of CH 4 and N 2 O on a 100-year horizon for the CI rotation systems was 2720.35 kg CO 2 ha −1 , which was 41.1% lower than that for the TI fields ( p < 0.05). Moreover, the difference of rice and wheat yields between the CI and TI fields was not significant ( p > 0.05). This is the first study to investigate the effects of CI during the rice season on the annual integrative GWP of CH 4 and N 2 O in a rice–winter wheat rotation system. Our results suggest that CI can significantly mitigate the annual integrative greenhouse effect caused by CH 4 and N 2 O from the rice–winter wheat rotation systems, while ensuring the crop yields. [ABSTRACT FROM AUTHOR]

Biochar application (BA) and controlled irrigation (CI) can realize the resource utilization of biowaste and water respectively. Both BA and CI can affect soil carbon pool dynamics and greenhouse gas (GHG) emissions in paddy fields, but their synergistic effects and the microbial mechanism remain unclear. This study investigated the effects of BA on CO 2 exchange, GHG emissions, and soil microbial diversity of paddy fields under CI. BA increased soil respiration rate (R s) from CI paddy fields by 23.81%–41.45 %, possibly due to the increase of Curvibacter , while BA reduced global warming potential by 25.85%–37.84 %. The reduction of N 2 O emission under CI with BA may be attributed to the increase of Proteobacteria and the decrease of Nitrospira. CI decreased the net ecosystem exchange (NEE) and soil organic carbon but increased R s and dissolved organic carbon, compared with flood irrigation. Lactobacillus and Mortierella were dominant bacteria and fungi at milk stage. In addition, BA and CI mitigated CH 4 emissions and reduced the abundance of Russula. Both bacteria and fungi play important roles in soil carbon cycle, which is mainly affected by soil temperature, humidity, and ammonium. These results indicate that BA combined with CI is a promising cleaner production strategy to simultaneously improve soil health, mitigate GHG emission, and mediate soil microbial community structure. [Display omitted] • Biochar decreased the global warming potential by 25.85%–37.84 %. • Biochar reduced N 2 O emission via enriching Proteobacteria and reducing Nitrospira. • Biochar increased soil respiration by 23.81%–41.45 % via enriching Curvibacter. • Both biochar and controlled irrigation reduced Russula and mitigated CH 4 emissions. • Biochar decreased the abundance of Mortierella , thereby increased soil carbon pool. [ABSTRACT FROM AUTHOR]

Guangzhou city in South China has experienced an accelerated urban development since the 1980s. This paper examines the impact of the urban development on urban heat islands through a historical analysis of urban–rural air temperature differences. Remote sensing techniques were applied to derive information on land use/cover and land surface temperatures and to assess the thermal response patterns of land cover types. The results revealed an overriding importance of urban land cover expansion in the changes in heat island intensity and surface temperature patterns. Urban development was also related to a continual air temperature increase in the 1980s and 1990s. The combined use of satellite-derived vegetation and land cover distributions with land surface temperature maps provides a potential useful tool for many planning applications. The city''s greening campaigns and landscaping designs should consider the different cooling effects of forest, shrubs and grassy lawns for temperature control and should plant more tall trees. [Copyright &y& Elsevier]

Biochar has been widely applied to paddy fields to improve soil fertility, crop productivity and carbon sequestration, thereby leading to variations in the CO 2 exchange between the paddy fields under flooding irrigation and the atmosphere, as indicated by many previous reports. However, few relevant reports have focused on paddy fields under water-saving irrigation. This study conducted a field experiment to investigate the effects of three biochar addition rates (0, 20 and 40 t ha−1) on the CO 2 exchange between paddy fields under controlled irrigation (CI, a water-saving irrigation technique) and the atmosphere in the Taihu Lake region of Southeast China. Our results showed that biochar addition increased the paddy field ecosystem respiration (R eco) and the soil respiration rate (R s) in the CI paddy fields. And biochar application increased the total CO 2 emissions and the total soil CO 2 emissions, especially at a rate of 40 t ha−1. In contrast, gross primary productivity (GPP) was decreased and the net ecosystem exchange of CO 2 (NEE) was increased with biochar addition. However, biochar addition at a rate of 20 t ha−1 significantly increased the total CO 2 absorption and the net CO 2 absorption of the CI paddy fields (p < 0.05), whereas biochar addition at a rate of 40 t ha−1 had no effect on the total CO 2 absorption and decreased the total net CO 2 absorption. At the same time, biochar addition significantly increased soil catalase, invertase and urease activities and contributed substantially to the increase in soil invertase activity. In addition, the soil bacterial, fungal and actinomycetal abundances were evidently increased with biochar addition, of which the soil fungal abundance showed the greatest increase. A high correlation was observed between soil catalase and invertase activities and soil microbial abundance. R eco was highly correlated with air and soil temperatures and soil enzyme activity. A significant quadratic polynomial correlation was observed between GPP and leaf area index (p < 0.01). The combination of biochar addition at a rate of 20 t ha−1 and water-saving irrigation has the potential to increase the size of the carbon sink and promote soil enzyme and microbial activities in paddy field ecosystems. • Biochar addition increased R eco, R s and NEE and decreased GPP of CI paddy fields. • Total CO 2 emissions and soil CO 2 emissions increased with biochar addition rates. • Biochar addition increased soil enzyme and microbial activities of CI paddy fields. • Soil catalase and invertase activities were highly correlated to microbial abundance. • Air and soil temperatures, soil enzyme activity and LAI affected CO 2 exchange. [ABSTRACT FROM AUTHOR]

[Display omitted] • nZVI exposure increased the antibiotic resistome in anaerobic digestion. • Efflux pump and rRNA methyltransferase shaped the antibiotic resistome variation. • Improved adaptability of efflux pump benefited the anaerobes withstanding nZVI. • Increased acquisition of rRNA methyltransferase preserved the structure of protein. • Polyspecificity of multidrug resistance drove the ARGs evolution in anaerobes. Nano zero-valent iron (nZVI) assisted anaerobic digestion (AD) is considered an effective approach for mediating antibiotic resistance genes (ARGs) dissemination in activated sludge. However, little is known about the mechanisms that drive antibiotic resistomes evolution in relation with their physiological roles distinct from protection of bacteria against antimicrobials. Metagenomic sequencing showed that efflux pumps and rRNA methyltransferase genes were the most prevalent ARGs in anaerobes, being responsible for the variations of antibiotic resistome upon nZVI addition. Particularly, to withstand the oxidative stimuli derived from initially 9 days nZVI exposure, genes involved in the two component systems (PhoRB , BaeSR , EvgSA) and global regulator networks (MarA , SoxS) were increased, activating the chromosomally encoded intrinsic efflux pumps expression. Furthermore, to benefit for survival, the polyspecific efflux pumps were involved in the microbial physiological adaptations of enhanced siderophores, lipid moieties, and quorum sensing molecules exportation, which induced the adaptative efflux pumps expression. On the other hand, to maintain the protein synthesis under oxidative condition, genes encoding Rsm, Erm, and Rlu family methyltransferases were notably up-regulated via horizontal transfer, inducing the acquired rRNA methylation resistance. Importantly, after prolonged exposure to nZVI for 18 and 27 days, the antibiotic resistomes were measurably decreased, due to the recovered oxidative state and increased membrane rigidity. Overall, these findings provide a deep understanding on the necessity of antibiotic resistome evolution for anaerobes to adapt to nZVI exposure for survival, which can be introduced to improve the ARGs risks analysis. [ABSTRACT FROM AUTHOR]

While vapor condensation in arid and semiarid areas has garnered much attention, such information is scarce for humid crop production areas such as rice fields. In a water-saving irrigation (WSI) rice field, high-precision weighed microlysimeters allowed the direct and independent quantification of condensation over plants (Cc) and soil (Cs) through mass balance calculations. The occurrence frequency and rate of Cc generally exceeded that of Cs. Predominantly occurring between sunset and sunrise, particularly between 0400 and 0500 local time, Cc showed an overall maximum rate of 0.096 mm h−1. In contrast, Cs was highest between 0100 and 1100 local time and showed an overall maximum rate of 0.044 mm h−1. The occurrence of Cc, unlike that of Cs, required a surface temperature lower than the ambient temperature or dewpoint. Of 65 rain-free days, Cc and Cs occurred on 60 and 33 days, respectively. Seasonal Cc, Cs, and Cc + Cs were estimated as 32.3, 3.1, and 35.4 mm, respectively, and their contributions to seasonal rice transpiration T, evaporation E, and evapotranspiration (ET) were 9.5%, 1.6%, and 6.7%, respectively. The seasonal Cc + Cs was similar in magnitude to a routine irrigation quota and accounted for 10.8% of rainfall and 14.4% of irrigation in the WSI rice field. Therefore, vapor condensation in rice fields in a subtropical monsoon climate is an important component of the hydrological cycle and cannot be ignored when tabulating the field water balance, calculating field water consumption, or in irrigation scheduling. [ABSTRACT FROM AUTHOR]

Water management is an important practice with significant effect on greenhouse gases (GHG) emission from soils. Nitrous oxide (N 2 O) and carbon dioxide (CO 2 ) emissions and their global warming potentials (GWPs) from subsurface watering soil (SUW) were investigated, with surface watering (SW) as a control. Results indicated that the N 2 O and CO 2 emissions from SUW soils were somewhat different to those from SW soil, with the peak N 2 O and CO 2 fluxes from SUW soil reduced by 28.9% and 19.4%, and appeared 72 h and 168 h later compared with SW. The fluxes of N 2 O and CO 2 from SUW soils were lower than those from SW soil in both pulse and post-pulse periods, and the reduction was significantly ( p < 0.05 ) in pulse period. Compare to SW, the cumulative N 2 O and CO 2 emissions and its integrative GWPs from SUW soil decreased by 21.0% ( p < 0.05 ), 15.9% and 18.0%, respectively. The contributions of N 2 O to GWPs were lower than those of CO 2 during most of time, except in pulse emission periods, and the proportion of N 2 O from SUW soil was 1.4% ( p > 0.1 ) lower that from SW soil. Moreover, N 2 O and CO 2 fluxes from both watering treatments increased exponentially with increase of soil water-filled pore space (WFPS) and temperature. Our results suggest that watering soil from subsurface could significantly reduce the integrative greenhouse effect caused by N 2 O and CO 2 and is a promising strategy for soil greenhouse gases (GHGs) mitigation. And the pulse period, contributed most to the reduction in emissions of N 2 O and CO 2 from soils between SW and SUW, should be a key period for mitigating GHGs emissions. Response of N 2 O and CO 2 emissions to soil WFPS and temperature illustrated that moisture was the dominant parameters that triggering GHG pulse emissions (especially for N 2 O), and temperature had a greater effect on the soil microorganism activity than moisture in drier soil. Avoiding moisture and temperature are appropriate for GHG emission at the same time is essential for GHGs mitigation, because peak N 2 O and CO 2 emission were observed only when moisture and temperature are both appropriate. [ABSTRACT FROM AUTHOR]

Partial wetting irrigation influences soil moisture distribution, which potentially changes soil nitrous oxide (N 2 O) emission. Incubation experiments were conducted to reveal the impact of non-uniform moisture distribution on soil N 2 O emissions under subsurface-drip-irrigation (SDI), with surface-irrigation (SI) as a control. Results indicated that soil N 2 O emission from different subregions of SDI soil varied synchronized to soil moisture. The wetting-drying process in different soil subregions under SDI incurred pulse N 2 O emissions unexceptionally, but the pulse magnitudes and timing of the occurrence varied among subregions. The pulse N 2 O emission magnitudes positively correlated to the match degree of soil moisture to the optimal soil moisture level for peak N 2 O emissions. The soil water-filled-porosity WFPS ranges for peak N 2 O fluxes, the determine coefficient of the exponential functions between N 2 O flux and soil WFPS and its average slopes, decreased gradually from the central to periphery SDI soil subregions. Both peak and cumulative N 2 O fluxes were much lower from the periphery subregions than from central subregions. On the whole, SDI reduced the cumulative N 2 O emissions by 77.3–86.7% compared to SI, with periphery suberegions of R3 and R4 contributing for more than 76%. The partial wetting SDI irrigation can significantly reduce soil N 2 O emissions and is a promising strategy for soil N 2 O emission mitigation. Further research should be conducted on how to design SDI properly to balance the soil moisture uniformity/efficiency and soil N 2 O emission reduction. [ABSTRACT FROM AUTHOR]

Surface energy distribution in paddy fields and the ratio of latent heat flux (LE) to available energy, termed as the evaporative fraction (EF), are essential for an understanding of water and energy processes. They are expected to vary in different ways in response to changes in the soil moisture condition under water-saving irrigation practice. In this study, the diurnal and seasonal variations in energy distribution were examined based on the data measured by the eddy covariance system and corrected with enforcing energy balance closure by the EF method in water-saving irrigated rice paddies in 2015 and 2016. Soil heat flux (G) values were similar in magnitude to sensible heat flux (Hs) values, with both accounting for approximately 5% of the energy input. Both magnitudes of G and Hs were significantly lower than that of LE. Generally, EF in water-saving irrigated rice paddies was larger than that of other ecosystems, and varied within a narrow range from 0.7 to 1.0. Diurnally, EF decreased till noon and then increased slowly in the afternoon till sunset. It was found be less varied between 10:00 and 14:00. Seasonally, the alternative drying-wetting soil water conditions in water-saving irrigated rice paddies resulted in a change in the variation of the EF. The LE flux is the largest component of available energy, with EF being mostly higher than 0.9. EF, increasing consistently till the tillering stage, remaining high from the late tillering to milk stage, and then following a declining trend. The maximum EF (approaching 1.0) was found in the milk stage. The results of EF in water-saving irrigated rice paddies will be helpful for estimating daily or long temporal scale evapotranspiration (ET) by the EF method based on satellite-derived ET. [ABSTRACT FROM AUTHOR]

Abstract: Water management is one of the most important practices that affect methane (CH4) and nitrous oxide (N2O) emissions from paddy fields. A field experiment was designed to study the effects of controlled irrigation (CI) on CH4 and N2O emissions from paddy fields, with traditional irrigation (TI) as the control. The effects of CI on CH4 and N2O emissions from paddy fields were very clear. The peaks of CH4 emissions from the CI paddies were observed 1–2d after the water layer disappeared. Afterward, the emissions reduced rapidly and remained low until the soil was re-flooded. A slight increase of CH4 emission was observed in a short period after re-flooding. N2O emissions peaks from CI paddies were all observed 8–10d after the fertilization at the WFPS ranging from 78.1% to 85.3%. Soil drying caused substantial N2O emissions, whereas no substantial N2O emissions were observed when the soil was re-wetted after the dry phase. Compared with TI, the cumulative CH4 emissions from the CI fields were reduced by 81.8% on the average, whereas the cumulative N2O emissions were increased by 135.4% on the average. The integrative global warming potential of CH4 and N2O on a 100-year horizon decreased by 27.3% in the CI paddy fields, whereas no significant difference in the rice yield was observed between the CI and TI fields. These results suggest that CI can effectively mitigate the integrative greenhouse effect caused by CH4 and N2O emissions from paddy fields while ensuring the rice yield. [Copyright &y& Elsevier]

Photosynthetic light response (PLR) curves of leaves are usually fitted by non-rectangular hyperbola (NRH) equation, and those fitted NRH parameters may change with leaf aging. The objectives of this study were 1) to reveal the response of NRH parameters of rice leaves, light-saturated net photosynthetic rate (Pnmax), quantum yield of assimilation (φ), dark respiration rate (Rd) and convexity of the curve (k), to leaf age; and 2) to improve the performance of NRH equation in simulating the PLR curves for leaves at various ages. The PLR for rice leaves at ages of 3–53 days were measured, and the general NRH equation was developed by incorporating the relationship between NRH parameters and leaf age into the NRH equation. The results showed that the NRH parameters of Pnmax, φ and Rd increased rapidly to maximum at approximately 10 days and then declined linearly toward the age of 53 days. However, the value of k was not sensitive to leaf age. The general NRH equation can be used to simulate leaf PLR continuously along with leaf aging. [ABSTRACT FROM AUTHOR]