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Soil is an important element in the agricultural domain because it serves as the media that bridges the water consumption and supply processes. In this study, a neural network ensemble (NNE) method was employed to predict the soil moisture to eliminate the effects of random initial parameters of neural network (NN) on model accuracy. The constructed NNE model predicts daily root zone soil moisture continuously for the whole crop growing season and the water consumption and supply processes were separately modeled. The soil profile was divided into multiple layers and modeled separately. Weather data (including air temperature, humidity, wind speed, net radiation, and precipitation), rooting depth, and the hesternal soil moisture of each layer were used as the input. A calibrated root zone water quality model for maize (Zea mays L.) was used to generate training and evaluation data. The result showed that with 100 randomly initialized NN models, the NNE model achieved an average R2 of 0.96 and nRMSE of 5.93%, suggesting that the NNE model learned the soil moisture dynamics well and sufficiently improved the robustness of soil moisture prediction with high accuracy.
Zhe Gu; Tingting Zhu; Xiyun Jiao; Junzeng Xu; Zhiming Qi. Evaluating the Neural Network Ensemble Method in Predicting Soil Moisture in Agricultural Fields. Agronomy 2021, 11, 1521 .
AMA StyleZhe Gu, Tingting Zhu, Xiyun Jiao, Junzeng Xu, Zhiming Qi. Evaluating the Neural Network Ensemble Method in Predicting Soil Moisture in Agricultural Fields. Agronomy. 2021; 11 (8):1521.
Chicago/Turabian StyleZhe Gu; Tingting Zhu; Xiyun Jiao; Junzeng Xu; Zhiming Qi. 2021. "Evaluating the Neural Network Ensemble Method in Predicting Soil Moisture in Agricultural Fields." Agronomy 11, no. 8: 1521.
In southern China, the growing period of rice is synchronized with the rainy period, and the loss of nutrients (such as nitrogen) due to unreasonable irrigation and drainage, along with rainfall and runoff, has become the main source of agricultural nonpoint source pollution. The laws of runoff and nitrogen loss in paddy fields under different irrigation and drainage modes are not clear. In this study, field experiments were adopted to observe the runoff and nitrogen loss under typical rainfall and throughout the whole growth period. The results showed that, compared with the traditional irrigation and drainage mode, the controlled irrigation and drainage mode reduced the drainage of two typical rainfall processes by 47.5% and 31.3% and the peak drainage by 38.9% and 14.4%. Compared with those under the traditional irrigation and drainage mode, the average concentrations of total nitrogen, nitrate nitrogen, and ammonium nitrogen under the controlled irrigation and drainage mode were reduced by 22.2%, 22.7%, and 27.8%, respectively, during the whole rainfall process on July 21 and were decreased by 27.1%, 11.4%, and 25.6%, respectively, on August 25. In irrigated rice areas, under the controlled irrigation and drainage mode, drainage was reduced after two intercepts through paddy fields and drainage ditches. The nitrogen concentration in the drainage ditch decreased due to the increase in retention time and the effect of the ditch and field wetland. Compared with the traditional irrigation and drainage mode, the total nitrogen, nitrate nitrogen, and ammonium nitrogen loads of the controlled irrigation and drainage mode were reduced by 69.8%, 65.3%, and 69.7%, respectively.
Yanmei Yu; Junzeng Xu; PingCang Zhang; Yan Meng; Yujiang Xiong. Controlled Irrigation and Drainage Reduce Rainfall Runoff and Nitrogen Loss in Paddy Fields. International Journal of Environmental Research and Public Health 2021, 18, 3348 .
AMA StyleYanmei Yu, Junzeng Xu, PingCang Zhang, Yan Meng, Yujiang Xiong. Controlled Irrigation and Drainage Reduce Rainfall Runoff and Nitrogen Loss in Paddy Fields. International Journal of Environmental Research and Public Health. 2021; 18 (7):3348.
Chicago/Turabian StyleYanmei Yu; Junzeng Xu; PingCang Zhang; Yan Meng; Yujiang Xiong. 2021. "Controlled Irrigation and Drainage Reduce Rainfall Runoff and Nitrogen Loss in Paddy Fields." International Journal of Environmental Research and Public Health 18, no. 7: 3348.
Soil organic carbon (SOC) conservation in agricultural soils is vital for sustainable agricultural production and climate change mitigation. To project changes of SOC and rice yield under different water and carbon management in future climates, based on a two-year (2015 and 2016) field test in Kunshan, China, the Denitrification Decomposition (DNDC) model was modified and validated and the soil moisture module of DNDC was improved to realize the simulation under conditions of water-saving irrigation. Four climate models under four representative concentration pathways (RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5), which were integrated from the fifth phase of the Coupled Model Intercomparison Project (CMIP5), were ensembled by the Bayesian Model Averaging (BMA) method. The results showed that the modified DNDC model can effectively simulate changes in SOC, dissolved organic carbon (DOC), and rice yield under different irrigation and fertilizer management systems. The normalized root mean squared errors of the SOC and DOC were 3.45–17.59% and 8.79–13.93%, respectively. The model efficiency coefficients of SOC and DOC were close to 1. The climate scenarios had a great impact on rice yield, whereas the impact on SOC was less than that of agricultural management measures on SOC. The average rice yields of all the RCP 2.6, RCP 4.5, RCP 6.0, and RCP 8.5 scenarios in the 2090s decreased by 18.41%, 38.59%, 65.11%, and 65.62%, respectively, compared with those in the 2020s. The long-term effect of irrigation on the SOC content of paddy fields was minimal. The SOC of the paddy fields treated with conventional fertilizer decreased initially and then remained unchanged, while the other treatments increased obviously with time. The rice yields of all the treatments decreased with time. Compared with traditional management, controlled irrigation with straw returning clearly increased the SOC and rice yields of paddy fields. Thus, this water and carbon management system is recommended for paddy fields.
Zewei Jiang; Shihong Yang; Jie Ding; Xiao Sun; Xi Chen; Xiaoyin Liu; Junzeng Xu. Modeling Climate Change Effects on Rice Yield and Soil Carbon Under Variable Water and Nutrient Management. Sustainability 2021, 13, 568 .
AMA StyleZewei Jiang, Shihong Yang, Jie Ding, Xiao Sun, Xi Chen, Xiaoyin Liu, Junzeng Xu. Modeling Climate Change Effects on Rice Yield and Soil Carbon Under Variable Water and Nutrient Management. Sustainability. 2021; 13 (2):568.
Chicago/Turabian StyleZewei Jiang; Shihong Yang; Jie Ding; Xiao Sun; Xi Chen; Xiaoyin Liu; Junzeng Xu. 2021. "Modeling Climate Change Effects on Rice Yield and Soil Carbon Under Variable Water and Nutrient Management." Sustainability 13, no. 2: 568.
Process-based coupled model of stomatal conductance–photosynthesis–transpiration was developed to estimate simultaneously stomatal conductance gsw, photosynthetic rate Pn, and transpiration rate Tr during leaf ontogeny. The modified Jarvis model was constructed by superposing the influence of leaf age LA on gsw in traditional Jarvis model. And the modified Farquhar model was constructed by incorporating the relationships of the LA with parameters in Farquhar model into traditional Farquhar model. The average and leaf-age-based coupled models were constructed, respectively, by combining traditional Farquhar and Penman–Monteith models with traditional Jarvis, and combining modified Farquhar and Penman–Monteith models with modified Jarvis. The results showed that the gsw, the maximum rate of carboxylation, maximum rate of electron transport, rate of triose phosphates utilization, and mitochondrial respiration rate varied in a positive skew pattern, while the mesophyll diffusion conductance decreased linearly with increase in LA. The average coupled model underestimated gsw, Pn, and Tr for young leaves and overestimated gsw, Pn, and Tr for old leaves. And the leaf-age-based coupled model generally perfected well in estimating gsw, Pn, and Tr for all leaves during leaf ontogeny. The study will provide basic information for either modeling leaf gsw, Pn, and Tr continuously, or upscaling them from leaf to canopy scale by considering the variation of LA within canopy.
Yuping Lv; Junzeng Xu; Xiaoyin Liu. A process-based coupled model of stomatal conductance–photosynthesis–transpiration during leaf ontogeny for water-saving irrigated rice. Photosynthesis Research 2021, 147, 145 -160.
AMA StyleYuping Lv, Junzeng Xu, Xiaoyin Liu. A process-based coupled model of stomatal conductance–photosynthesis–transpiration during leaf ontogeny for water-saving irrigated rice. Photosynthesis Research. 2021; 147 (2):145-160.
Chicago/Turabian StyleYuping Lv; Junzeng Xu; Xiaoyin Liu. 2021. "A process-based coupled model of stomatal conductance–photosynthesis–transpiration during leaf ontogeny for water-saving irrigated rice." Photosynthesis Research 147, no. 2: 145-160.
Rice is a staple food crop that provides more calories to the global population than any other crop. Rice production is also a major consumer of fresh-water resources. Hence, changes in rice evapotranspiration (ETc) due to projected warming patterns is becoming necessary in any management of water resources and food security assessments. Here, air temperature (Ta) measurements from 1003 meteorological stations covering the period from 1967 to 2016 in China, Japan and the Philippines are first used to assess warming trends. Energy fluxes were then assembled so as to evaluate the responses of rice ETc to various warming trends. A modified Priestley-Taylor formulation was used to interpret ETc under differing warming scenarios. Results showed that the average values of daily mean Ta from 1997–2016 increased by 4.6% relative to the period from 1967–1996, where 85% of all stations marked an increase of 0.5–1.5 °C. Greater increment in average daily minima in Ta (5.1%) was noted in the past 20 years compared to the average daily maximum in Ta (3.7%), showing asymmetric warming. The changed growth duration linearly decreased as ambient seasonal mean Ta increased, and higher temperature sensitivity of altered growth duration occurred at greater warming level. Overall, the proposed modified Priestley-Taylor model can be used for estimating ETc of rice for both half-hourly and daily scales provided the growth duration is a priori known. Changes in seasonal ETc of rice under varying types of warming patterns are largely explained by both ambient seasonal mean Ta and changes in growth duration.
Rangjian Qiu; Gabriel G. Katul; Jintao Wang; Junzeng Xu; Shaozhong Kang; Chunwei Liu; Baozhong Zhang; Longan Li; Edward P. Cajucom. Differential response of rice evapotranspiration to varying patterns of warming. Agricultural and Forest Meteorology 2020, 298-299, 108293 .
AMA StyleRangjian Qiu, Gabriel G. Katul, Jintao Wang, Junzeng Xu, Shaozhong Kang, Chunwei Liu, Baozhong Zhang, Longan Li, Edward P. Cajucom. Differential response of rice evapotranspiration to varying patterns of warming. Agricultural and Forest Meteorology. 2020; 298-299 ():108293.
Chicago/Turabian StyleRangjian Qiu; Gabriel G. Katul; Jintao Wang; Junzeng Xu; Shaozhong Kang; Chunwei Liu; Baozhong Zhang; Longan Li; Edward P. Cajucom. 2020. "Differential response of rice evapotranspiration to varying patterns of warming." Agricultural and Forest Meteorology 298-299, no. : 108293.
Infrared thermal imaging cameras are effective tools to monitor the spatial distribution of canopy temperature (Tc), which is the basis of the crop water stress index (CWSI) calculation. This paper presents a new method to improve the CWSI performance in crop water stress diagnosis based on Tc measured by thermal imaging. Cumulative frequency curves of pixel Tc extracted from each thermal image were analysed. Different statistical quantiles of Tc were determined, and the average Tc over different statistics quantiles were used to calculate the CWSI separately. There were large gaps among the CWSI based on Tc over different statistical quantiles. We compared the coefficient of determination (R2) of relationships among the CWSI based on Tc over different statistical quantiles and relative leaf photosynthetic activities. The general sensitive CWSI showed the best correlations with leaf photosynthetic activities, which were calculated based on average values of the top 60%, 50%, 70%, 50% of Tc statistics at different growth stages. The ranges of the CWSI with optimal leaf water use efficiency (between turning-points for downward trends in photosynthesis and transpiration) were 0.556–0.569, 0.481–0.486, 0.571–0.641, and 0.511–0.606 at tillering, panicle initiation to booting, heading to anthesis, and milk to soft dough stages respectively. The corresponding soil moisture levels were consistent with the lower thresholds of the rice under control irrigation. Based on the spatial distribution of canopy temperatures measured by thermal imaging cameras, the general sensitive CWSI, which was calculated by removing low temperatures, had a better performance in crop water stress diagnosis.
Yajun Luan; Junzeng Xu; Yuping Lv; Xiaoyin Liu; Haiyu Wang; Shimeng Liu. Improving the performance in crop water deficit diagnosis with canopy temperature spatial distribution information measured by thermal imaging. Agricultural Water Management 2020, 246, 106699 .
AMA StyleYajun Luan, Junzeng Xu, Yuping Lv, Xiaoyin Liu, Haiyu Wang, Shimeng Liu. Improving the performance in crop water deficit diagnosis with canopy temperature spatial distribution information measured by thermal imaging. Agricultural Water Management. 2020; 246 ():106699.
Chicago/Turabian StyleYajun Luan; Junzeng Xu; Yuping Lv; Xiaoyin Liu; Haiyu Wang; Shimeng Liu. 2020. "Improving the performance in crop water deficit diagnosis with canopy temperature spatial distribution information measured by thermal imaging." Agricultural Water Management 246, no. : 106699.
The trend of wetting or drying is an important metric of regional and global climate change. Based on daily meteorological data during 1951–2018 from 10 stations in arid regions of North China, the performances of two indicators, relative humidity (RH) and actual water vapour pressure (ea), in evaluating the trends of air humidification are investigated. Results show that annual RH decreases by 0–0.10% yr−1 during the past decades in almost all (90%) stations, whereas annual ea presents increasing trends in 40% of stations and decreasing trends in the other 60% stations. Therefore, contrasting results are observed in the trends of air humidity reflected RH and ea. Specifically, stations getting significantly drying as indicated by RH, it is tend to getting less drying or even wetting as indicated by ea. These results suggest that it tend to give a misleading conclusion with the trends of RH as indicator in evaluating the trends of regional or global wetting or drying, due to the reduction in RH caused by the accompanying temperature rising under global warming. The other indicator ea is more consistent with the precipitation changes, and suitable for trending analyses of air humidification under such circumstance. Further researches should be done in a larger scale arid region and in different seasons, to investigate the differences in the trends of air humidification indicated by RH and ea, and discuss the response of the changes of wetting or drying to the varied meteorological factors.
Qi Wei; Junzeng Xu; Linxian Liao; Yanmei Yu; Weixuan Liu; Jing Zhou; Yimin Ding. Indicators for evaluating trends of air humidification in arid regions under circumstance of climate change: Relative humidity (RH) vs. Actual water vapour pressure (ea). Ecological Indicators 2020, 121, 107043 .
AMA StyleQi Wei, Junzeng Xu, Linxian Liao, Yanmei Yu, Weixuan Liu, Jing Zhou, Yimin Ding. Indicators for evaluating trends of air humidification in arid regions under circumstance of climate change: Relative humidity (RH) vs. Actual water vapour pressure (ea). Ecological Indicators. 2020; 121 ():107043.
Chicago/Turabian StyleQi Wei; Junzeng Xu; Linxian Liao; Yanmei Yu; Weixuan Liu; Jing Zhou; Yimin Ding. 2020. "Indicators for evaluating trends of air humidification in arid regions under circumstance of climate change: Relative humidity (RH) vs. Actual water vapour pressure (ea)." Ecological Indicators 121, no. : 107043.
Dissolved pollutant transport over the ground surface is one of the main contributors to water pollution in urban environment. However, existing widely applied transport models are semi-empirical and the mechanism of the dissolved pollutant runoff is still not well understood. A novel physically-based transport model for dissolved pollutant is herein proposed by adopting a “control layer” concept in the overland flow. This transport model assumes that the dissolved pollutant in the upper runoff water is completely mixed with that in the underneath control layer. To verify the proposed model, a series of laboratory experiments were conducted. It showed that the predictions made by the model are in good agreement with the experimental results. The depth of the control layer is mainly correlated with the bed slope and shows no obvious dependence on rainfall intensity. The minimum depth of the control layer is bounded by a limiting value. In addition, the maximum pollutant transport rate is found to occur at the time of concentration. The rainfall intensity, bed slope, surface roughness and catchment length are dominant factors that control the dissolved pollutant transport. The wash-off coefficient is a function of time and is found to be the reciprocal of the average water depth of the catchment area over which the equilibrium state has been reached. This study advances the understanding of the mechanism of the dissolved pollutant transport in urban environment.
Taotao Zhang; Yang Xiao; Dongfang Liang; Hongwu Tang; Junzeng Xu; Saiyu Yuan; Bin Luan. A physically-based model for dissolved pollutant transport over impervious surfaces. Journal of Hydrology 2020, 590, 125478 .
AMA StyleTaotao Zhang, Yang Xiao, Dongfang Liang, Hongwu Tang, Junzeng Xu, Saiyu Yuan, Bin Luan. A physically-based model for dissolved pollutant transport over impervious surfaces. Journal of Hydrology. 2020; 590 ():125478.
Chicago/Turabian StyleTaotao Zhang; Yang Xiao; Dongfang Liang; Hongwu Tang; Junzeng Xu; Saiyu Yuan; Bin Luan. 2020. "A physically-based model for dissolved pollutant transport over impervious surfaces." Journal of Hydrology 590, no. : 125478.
Rainfall occurs frequently in South China and results in recurring of drainage/discharge of nitrogen and phosphorus-rich water from paddy fields, which may cause serious non-point source pollution of receiving waters such as rivers. Moreover, time intervals between individual rainfall events are short (often only several days). Thus, not only is the treatment of discharge water needed, but a more rapid form of treatment is desired as well. On the basis of the literature, constructed wetlands could remove nitrogen and phosphorous from paddy field drainage/outflow, and effective microorganisms (EM) could also be added to enhance the removals. A field experiment was conducted to demonstrate the wetland effectiveness and EM enhancement. The experiment was conducted from June to October in 2016. By applying EM to constructed wetlands, after 8 days, concentrations of total nitrogen (TN), ammonium nitrogen (NH4 +-N), nitrate nitrogen (NO3 −-N), and total phosphorus (TP) were reduced by 88%, 91%, 89%, and 50%, respectively. Within the first 4 days, TN and TP concentrations were reduced by 78% and 40%, respectively, with EM application, in comparison to 50% and 20%, respectively, without EM application, representing additional respective reductions of 28% and 20% by applying EM. The results from the field experiment indicated a significant improvement of phosphorus and nitrogen removals by applying effective microorganisms.
Xiaotian Li; Qizhong Guo; Yintang Wang; Junzeng Xu; Qi Wei; Lina Chen; Linxian Liao. Enhancing Nitrogen and Phosphorus Removal by Applying Effective Microorganisms to Constructed Wetlands. Water 2020, 12, 2443 .
AMA StyleXiaotian Li, Qizhong Guo, Yintang Wang, Junzeng Xu, Qi Wei, Lina Chen, Linxian Liao. Enhancing Nitrogen and Phosphorus Removal by Applying Effective Microorganisms to Constructed Wetlands. Water. 2020; 12 (9):2443.
Chicago/Turabian StyleXiaotian Li; Qizhong Guo; Yintang Wang; Junzeng Xu; Qi Wei; Lina Chen; Linxian Liao. 2020. "Enhancing Nitrogen and Phosphorus Removal by Applying Effective Microorganisms to Constructed Wetlands." Water 12, no. 9: 2443.
Models capable of accurately calculating crop evapotranspiration (ET) are essential to improving water management at both the hydrological cycle and the agriculture irrigation project scale. Penman-Monteith (PM) and Shuttleworth-Wallace (SW) models based on the Jarvis-type canopy resistance (rc) model were used to calculate the hourly and daily ET of rice grown in East China under water-saving irrigation (WSI). The model parameters in rc and soil resistance (rss) were recalibrated to improve the accuracy of rice ET estimations. Notable, three improvements were made to the rc model: (i) model parameters were calibrated at the canopy scale, and a term of effective leaf area index was used to reflect the influence of canopy coverage; (ii) the coefficient a4 was used to reflect the influence of the specific soil moisture patterns under WSI practice; and (iii) for rice crops, soil moisture at saturation, rather than at field capacity for upland crops, served as a key parameter in the soil water response functions. Both PM and SW models generated similar rice ET outputs due to their common theoretical basis. Surprisingly, the PM model, with an appropriately adjusted rc value, performed better than the SW model in simulating hourly and daily rice ET under WSI practice, particularly during periods when canopy cover was either dense or sparse. Sensitivity analyses showed both models to be highly sensitive to changes in rc, and soil moisture (θ), the latter being one of the dominant contributors to variations in rc and rss. Accordingly, the PM model is recommended for the prediction of rice ET grown under WSI conditions in East China, with the caveat that both the rc and θ should be accurately quantified when used as inputs.
Xiaoyin Liu; Junzeng Xu; Weiguang Wang; Yuping Lv; Yawei Li. Modeling rice evapotranspiration under water-saving irrigation condition: Improved canopy-resistance-based. Journal of Hydrology 2020, 590, 125435 .
AMA StyleXiaoyin Liu, Junzeng Xu, Weiguang Wang, Yuping Lv, Yawei Li. Modeling rice evapotranspiration under water-saving irrigation condition: Improved canopy-resistance-based. Journal of Hydrology. 2020; 590 ():125435.
Chicago/Turabian StyleXiaoyin Liu; Junzeng Xu; Weiguang Wang; Yuping Lv; Yawei Li. 2020. "Modeling rice evapotranspiration under water-saving irrigation condition: Improved canopy-resistance-based." Journal of Hydrology 590, no. : 125435.
Nitrous oxide (N2O) as a by-product of soil nitrogen (N) cylces, its production may be affected by soil salinity which have been proved to have significant negative effect on soil N transformation processes. The response of N2O production across a range of different soil salinities is poorly documented; accordingly, we conducted a laboratory incubation experiment using an array of soils bearing six different salinity levels ranging from 0.25 to 6.17 dS m−1. With ammonium-rich organic fertilizer as their N source, the soils were incubated at three soil moisture ( θ ) levels—50%, 75% and 100% of field capacity ( θ fc )—for six weeks. Both N2O fluxes and concentrations of ammonium, nitrite and nitrate (NH4+-N, NO2−-N and NO3−-N) were measured throughout the incubation period. The rates of NH4+-N consumption and NO3−-N accumulation increased with increasing soil moisture and decreased with increasing soil salinity, while the accumulation of NO2−-N increased first then decreased with increasing soil salinity. N2O emissions were significantly promoted by greater soil moisture. As soil salinity increased from 0.25 to 6.17 dS m−1, N2O emissions from soil first increased then decreased at all three soil moisture levels, with N2O emissions peaking at electric conductivity (EC) values of 1.01 and 2.02 dS m−1. N2O emissions form saline soil were found significantly positively correlated to soil NO2−-N accumulation. The present results suggest that greater soil salinity inhibits both steps of nitrification, but that its inhibition of nitrite oxidation is stronger than that on ammonia oxidation, which leads to higher NO2−-N accumulation and enhanced N2O emissions in soil with a specific salinity range.
Yawei Li; Junzeng Xu; Boyi Liu; Haiyu Wang; Zhiming Qi; Qi Wei; Linxian Liao; Shimeng Liu. Enhanced N2O Production Induced by Soil Salinity at a Specific Range. International Journal of Environmental Research and Public Health 2020, 17, 5169 .
AMA StyleYawei Li, Junzeng Xu, Boyi Liu, Haiyu Wang, Zhiming Qi, Qi Wei, Linxian Liao, Shimeng Liu. Enhanced N2O Production Induced by Soil Salinity at a Specific Range. International Journal of Environmental Research and Public Health. 2020; 17 (14):5169.
Chicago/Turabian StyleYawei Li; Junzeng Xu; Boyi Liu; Haiyu Wang; Zhiming Qi; Qi Wei; Linxian Liao; Shimeng Liu. 2020. "Enhanced N2O Production Induced by Soil Salinity at a Specific Range." International Journal of Environmental Research and Public Health 17, no. 14: 5169.
To evaluate the effect of a nitrification inhibitor on reducing N2O emissions from saline soils, we undertook a field plot experiment with three salinity levels (non-saline, NS = 0.21 dS m−1; low saline, LS = 1.02 dS m−1; and high saline, HS = 5.23 dS m−1), factorially combined with two nitrification inhibitor treatments (with and without DMPP (3,4-dimethylpyrazole phosphate)). The low saline soil had the highest N2O flux peak and its cumulative N2O emissions were 2.2-fold those of the non-saline soil and 3.1-fold those of the high saline soil. Low salinity strongly inhibited nitrite oxidation and only slightly inhibited ammonia oxidation, which resulted in a high accumulation of NO2−-N and high N2O emissions. The nitrification inhibitor DMPP reduced cumulative N2O emissions (p < 0.05) by 61% in non-saline soil (reduction of 88.3 mg N m−2) and by 75% in low saline soil (reduction of 239.8 mg N m−2). DMPP offsets low salinity-induced high N2O emissions by inhibiting ammonia oxidation.
Yawei Li; Junzeng Xu; Xiaoyin Liu; Zhiming Qi; Haiyu Wang; Youjia Li; Linxian Liao. Nitrification inhibitor DMPP offsets the increase in N2O emission induced by soil salinity. Biology and Fertility of Soils 2020, 56, 1211 -1217.
AMA StyleYawei Li, Junzeng Xu, Xiaoyin Liu, Zhiming Qi, Haiyu Wang, Youjia Li, Linxian Liao. Nitrification inhibitor DMPP offsets the increase in N2O emission induced by soil salinity. Biology and Fertility of Soils. 2020; 56 (8):1211-1217.
Chicago/Turabian StyleYawei Li; Junzeng Xu; Xiaoyin Liu; Zhiming Qi; Haiyu Wang; Youjia Li; Linxian Liao. 2020. "Nitrification inhibitor DMPP offsets the increase in N2O emission induced by soil salinity." Biology and Fertility of Soils 56, no. 8: 1211-1217.
Ammonia (NH3) volatilization is one of the major forms of nitrogen (N) losses from soil after N fertilization, especially in salt-affected soil, which leads to low N use efficiency. To evaluate the effect of biochar on NH3 volatilization from salt-affected soil with two different N fertilizers (urea and ammonium sulfate (AS)), experiments were conducted with two salt-affected soils (electrical conductivity EC1:5 of 1.0 and 5.0 ds m−1, namely S1 and S2) and non-saline soil as control (S0, EC1:5 < 0.3 ds m−1). Biochar was applied to S1 and S2 at the dosage of 20 t ha−1. Results showed that increasing soil salinity significantly promoted NH3 volatilization by 38.7%–76.8% than control and AS treatments recorded higher NH3 volatilization than urea in all salinity levels. The addition of biochar decreased NH3 volatilization by 10.8%–20.9%. The proportion of cumulative NH3 volatilization in the first week to the whole experimental period was significantly higher in S1, and biochar addition can reduce the percentages of gaseous N losses. This study unravels the immense capability of salt-affected soil to aggravate N losses in the form of NH3 volatilization, and biochar can be used as a potential soil amendment in decreasing NH3 volatilization in salt-affected soil.
Shimeng Liu; Yawei Li; Junzeng Xu; Wenjin Ma; Boyi Liu; Haiyu Wang; Xiaoyin Liu; Yajun Luan. Biochar partially offset the increased ammonia volatilization from salt-affected soil. Archives of Agronomy and Soil Science 2020, 1 -15.
AMA StyleShimeng Liu, Yawei Li, Junzeng Xu, Wenjin Ma, Boyi Liu, Haiyu Wang, Xiaoyin Liu, Yajun Luan. Biochar partially offset the increased ammonia volatilization from salt-affected soil. Archives of Agronomy and Soil Science. 2020; ():1-15.
Chicago/Turabian StyleShimeng Liu; Yawei Li; Junzeng Xu; Wenjin Ma; Boyi Liu; Haiyu Wang; Xiaoyin Liu; Yajun Luan. 2020. "Biochar partially offset the increased ammonia volatilization from salt-affected soil." Archives of Agronomy and Soil Science , no. : 1-15.
Measured leaf photosynthetic light response (PLR) curves at different positions were fitted by non-rectangular hyperbola (NRH) equation to characterize vertical profile of parameters in NRH equation, namely maximum net photosynthetic rate Pnmax, initial quantum yield of assimilation φ, dark respiration rate Rd, and convexity of the curve k, at both jointing and heading stages within rice canopy. And leaf-position-specific and canopy average NRH equations were constructed respectively based on measured PLR curves at each specific leaf position and all measured PLR curves within rice canopy. The results showed that the Pnmax, φ, and Rd reached the maximum at the top second leaf and then decreased at jointing stage and decreased in downward leaves at heading stage. The k increased with lowering leaf position at both stages. The leaf-position-specific NRH equation performed well in estimating net photosynthetic rate Pn for all leaves at different positions and stages, while the canopy average NRH equation underestimated leaf Pn at upper canopy and overestimated Pn at lower canopy. The top fourth leaf was suitable for estimating photosynthetic parameters at canopy scale, as the Pnmax, φ, Rd, and k of the top fourth leaf were near to these parameters of rice canopy, and the canopy average NRH equation performed well in estimating leaf Pn for the top fourth leaf. The results will provide basic information for upscaling leaf photosynthesis to canopy scale.
Yuping Lv; Junzeng Xu; Xiaoyin Liu; Haiyu Wang. Vertical profile of photosynthetic light response within rice canopy. International Journal of Biometeorology 2020, 64, 1699 -1708.
AMA StyleYuping Lv, Junzeng Xu, Xiaoyin Liu, Haiyu Wang. Vertical profile of photosynthetic light response within rice canopy. International Journal of Biometeorology. 2020; 64 (10):1699-1708.
Chicago/Turabian StyleYuping Lv; Junzeng Xu; Xiaoyin Liu; Haiyu Wang. 2020. "Vertical profile of photosynthetic light response within rice canopy." International Journal of Biometeorology 64, no. 10: 1699-1708.
Hyporheic exchange is affected by bedform geometry, which induces complex flow paths within the bedform. Additional factors that influence flow and solute transport in the hyporheic zone are layered profile sediments and density-driven flow. This study explored the combined effects of these factors on hyporheic exchange through laboratory experiments and numerical simulations involving infiltrating solute displacing less-dense resident water in a layered bedform with a low permeability layer (LPL). The bedform consisted of three horizontal layers, in which the hydraulic conductivity of the middle layer (LPL) was less than that of the top (TL) and bottom layers (BL). The results demonstrated that a previously unexplored combination of mechanisms (density effects and layered bedform) produces irregular spatial patterns of solute transport in the hyporheic zone. For instance, the width of solute plume within the bottom layers becomes narrowed compared with tracer transport. With increasing density contrast between infiltrating solute and resident water, the solute plume becomes much narrower, forming fingers. Numerical modeling further shows that the hydraulic conductivity contrast (HCC) and relative thickness (RT) of the hyporheic zone layers also affect the spatial solute transport patterns. As the hydraulic conductivity contrast or relative thickness increases, the plume becomes much narrower. Horizontal ambient flow (HAF) dominated in the bottom layers, and lateral solute spreading and mixing intensified with a higher hydraulic conductivity contrast and relative thickness. Furthermore, the vertical solute plume was detached by the horizontal ambient flow in the bottom layers with a discontinuous low permeability layer, forming a discontinuous zone of vertical solute transport.
Qihao Jiang; Guangqiu Jin; Hongwu Tang; Chengji Shen; Mohsen Cheraghi; Junzeng Xu; Ling Li; D.A. Barry. Density-dependent solute transport in a layered hyporheic zone. Advances in Water Resources 2020, 142, 103645 .
AMA StyleQihao Jiang, Guangqiu Jin, Hongwu Tang, Chengji Shen, Mohsen Cheraghi, Junzeng Xu, Ling Li, D.A. Barry. Density-dependent solute transport in a layered hyporheic zone. Advances in Water Resources. 2020; 142 ():103645.
Chicago/Turabian StyleQihao Jiang; Guangqiu Jin; Hongwu Tang; Chengji Shen; Mohsen Cheraghi; Junzeng Xu; Ling Li; D.A. Barry. 2020. "Density-dependent solute transport in a layered hyporheic zone." Advances in Water Resources 142, no. : 103645.
Aquatic crop (Zizania latifolia Stapf–Ipomoea aquatica Forsk) wetlands were constructed to remove nitrogen (N) in drainage from paddy rice fields, with three different storage water depths (namely 4H, 7H and 10H, where H is the routine paddy drainage water depth). Concentrations of ammonium nitrogen (NH4+-N), nitrate nitrogen (NO3−-N) and total nitrogen (TN) during the first two drainage events were reduced within 8–14d of storing by 82.3–92.8%, 84.5–94.3% and 74.9–92.4%, respectively. Generally, the higher N concentration in inlet water, the higher removal efficiency of nitrogen. The removal rate in wetland with 4H water storage was observed higher as compared to those at 7H and 10H. Overall, the aquatic crop wetlands at these storage water depths could intercept more than 93.2% of N output from paddy fields, and the removal efficiency was slightly better in wetland at 4H. For a routine drainage event (about 30–50 mm) occurred following a routine rainfall (about 100 mm at 5–10 years return period) with local water-level management practice in rice field, wetlands with 4H and 7H storage could effectively remove N in drainage by reusing it with aquatic crops. Nevertheless, the larger the proportion (low water depth in wetland for one drainage) of wetland to paddy field, the higher the production efficiency, because the value of aquatic vegetable is much higher than rice. The current results suggested that aquatic crop wetlands constructed in low-lying part within paddy fields could intercept a large amount of N output from paddy field, and with high economic return. Designing wetlands and paddy fields in a proper area ratio is vital important for balancing removal effect of nutrients in paddy drainage and the demand of food security.
Qi Wei; Jintao Liu; Yihao Peng; Junzeng Xu; Linxian Liao; Shihong Yang. Storing and removing nitrogen in drainage from paddy field by using aquatic crops wetland. Paddy and Water Environment 2020, 18, 587 -594.
AMA StyleQi Wei, Jintao Liu, Yihao Peng, Junzeng Xu, Linxian Liao, Shihong Yang. Storing and removing nitrogen in drainage from paddy field by using aquatic crops wetland. Paddy and Water Environment. 2020; 18 (3):587-594.
Chicago/Turabian StyleQi Wei; Jintao Liu; Yihao Peng; Junzeng Xu; Linxian Liao; Shihong Yang. 2020. "Storing and removing nitrogen in drainage from paddy field by using aquatic crops wetland." Paddy and Water Environment 18, no. 3: 587-594.
Rice water-saving irrigation technology can remarkably reduce irrigation water input and maintain high yield; however, this technology can also accelerate the decomposition of soil organic matter in paddy fields. The spatial and temporal distributions of soil organic carbon (SOC), water-soluble organic carbon (WSOC), and soil microbial biomass carbon (SMBC) under different water-carbon regulation scenarios were analyzed on the basis of field experiments in the Taihu Lake region in China to explore the effects of biochar application on SOC and its components in water-saving irrigation paddy fields. The response of soil catalase (CAT) and invertase (INV) to biochar application in water-saving irrigated rice fields was clarified. The results showed that water-saving irrigation reduced the SOC content by 5.7% to 13.3% but increased WSOC and SMBC contents by 13.8% to 26.1% and 0.9% to 11.1%, respectively, as compared with flooding irrigation. Nonflooding management promoted the oxidative decomposition of soil organic matter. Two years after straw biochar was added, paddy soil SOC content under water-saving irrigation was increased by 4.0% to 26.7%. The WSOC and SMBC contents were also increased by 4.0% to 52.4% and 7.0% to 40.8%, respectively. The high straw biochar addition rate exhibited great impact on SOC. Remarkable correlations among SOC, WSOC, and SMBC were observed, indicating that the addition of straw biochar improved soil labile C, such as WSOC and SMBC, which promoted SOC transformation and stability in paddy soil under water-saving irrigation. Soil CAT and INV were related to SOC conversion. In conclusion, the combination of water-saving irrigation and straw biochar addition was beneficial to the improvement of soil properties and fertility of paddy fields.
Shihong Yang; Xi Chen; Zewei Jiang; Jie Ding; Xiao Sun; Junzeng Xu. Effects of Biochar Application on Soil Organic Carbon Composition and Enzyme Activity in Paddy Soil under Water-Saving Irrigation. International Journal of Environmental Research and Public Health 2020, 17, 333 .
AMA StyleShihong Yang, Xi Chen, Zewei Jiang, Jie Ding, Xiao Sun, Junzeng Xu. Effects of Biochar Application on Soil Organic Carbon Composition and Enzyme Activity in Paddy Soil under Water-Saving Irrigation. International Journal of Environmental Research and Public Health. 2020; 17 (1):333.
Chicago/Turabian StyleShihong Yang; Xi Chen; Zewei Jiang; Jie Ding; Xiao Sun; Junzeng Xu. 2020. "Effects of Biochar Application on Soil Organic Carbon Composition and Enzyme Activity in Paddy Soil under Water-Saving Irrigation." International Journal of Environmental Research and Public Health 17, no. 1: 333.
Environmental concerns about the release of reactive nitrogen (N) from intensively fertilized farmland are growing, especially regarding gaseous N losses in the form of ammonia (NH3) and nitrous oxide (N2O). While saline soils are widely distributed and gradually expanding worldwide, the effect of soil salinity on soil NH3 and N2O emissions is poorly understood. To assess the effect of soil salinity levels on NH3 volatilization and N2O emissions, a field experiment was conducted with three soil salinity levels (S0 = non-saline, S1 = 1.0 dS m−1 and S2 = 5.0 dS m−1) and two N fertilizer types (urea and ammonium sulphate). Compared to the non-saline soil, S1 and S2 salinity levels both led to significant increases in cumulative NH3 volatilization losses by 40.0%–65.2% and 89.0%–92.2%, respectively (p < 0.05). Following the application of either urea and ammonium sulphate, N2O emissions at the S1 salinity level were significantly greater than those at both S0 and S2 salinity levels (p < 0.05). The correlation showed that the NH3 flux was an exponential function with respect to soil ammonium (NH4+-N) concentration (R2 = 0.766, p < 0.05), and the N2O flux displayed a linear relationship with soil nitrite (NO2−-N) concentration (R2 = 0.816, p < 0.05) which was accumulated to a much greater degree under the S1 salinity level. Saline soil’s promotion of NH3 volatilization was a result from urea hydrolysis, nitrification and soil NH4+-N adsorption capacity being suppressed under elevated soil salinity. Increased N2O emissions were ascribed to the accumulation of soil NO2−-N caused by the imbalance of salinity’s inhibition on nitrite oxidation and ammonia oxidation. This study indicates that saline soils have a considerable potential to simultaneously increase NH3 and N2O emissions, so mitigation options should be explored when cultivating saline soils.
Yawei Li; Junzeng Xu; Shimeng Liu; Zhiming Qi; Haiyu Wang; Qi Wei; Zhe Gu; Xiaoyin Liu; Fazli Hameed. Salinity-induced concomitant increases in soil ammonia volatilization and nitrous oxide emission. Geoderma 2019, 361, 114053 .
AMA StyleYawei Li, Junzeng Xu, Shimeng Liu, Zhiming Qi, Haiyu Wang, Qi Wei, Zhe Gu, Xiaoyin Liu, Fazli Hameed. Salinity-induced concomitant increases in soil ammonia volatilization and nitrous oxide emission. Geoderma. 2019; 361 ():114053.
Chicago/Turabian StyleYawei Li; Junzeng Xu; Shimeng Liu; Zhiming Qi; Haiyu Wang; Qi Wei; Zhe Gu; Xiaoyin Liu; Fazli Hameed. 2019. "Salinity-induced concomitant increases in soil ammonia volatilization and nitrous oxide emission." Geoderma 361, no. : 114053.
Evaporative fraction (EF), which is known to exhibit variation in response to changes in crop species, soil and meteorologic conditions, plays an important role in interpreting the components of energy budget and estimating evapotranspiration (ET), while such information is scarce for humid rice fields. The present study discussed the variation of energy balance components and then examined the pattern of hourly, daytime and daily EF after monitoring energy components by eddy covariance for water-saving irrigated (WSI) rice paddies of 2015 and 2016. Then the daily ET was estimated by an improved EF up-scaling method in the subtropical monsoon climate region of East China. Diurnally, hourly EF is deemed as an approximately concave-up shape in different growth stages of rice season. The seasonal average EF varies gently, with a minimum around 10:00–11:00 AM. Seasonally, the mean daytime EF for the whole growth stage is 0.86, 7% lower than the daily value. Daily EF exhibits mostly higher than 0.8 except later yellow ripening period, approaching 1.0 in the milk stage. EF over WSI rice exhibits obviously greater than the reports that from upland crops. In addition, differences are noted in the results with respect to the daily ET estimation by EF up-scaling method. The estimated daily ET (ETEF,d) from hourly EF during 10:00–11:00 h is highly correlated to the measured ET (ETtrue) by the weighed micro-lysimeters though the ETEF,d value is underestimated. Such a considerable gap serves in forming a relationship between ETEF,d and ETtrue,d, that is, by simply multiplying the representativeness ET value based on the EF up-scaling method by a correction procedure calibrated for this region. In conclusion, an improved EF up-scaling method is proposed for extrapolating remote sensing based ET estimates to daily values.
Xiaoyin Liu; Junzeng Xu; Xinyi Zhou; Weiguang Wang; Shihong Yang. Evaporative fraction and its application in estimating daily evapotranspiration of water-saving irrigated rice field. Journal of Hydrology 2019, 584, 124317 .
AMA StyleXiaoyin Liu, Junzeng Xu, Xinyi Zhou, Weiguang Wang, Shihong Yang. Evaporative fraction and its application in estimating daily evapotranspiration of water-saving irrigated rice field. Journal of Hydrology. 2019; 584 ():124317.
Chicago/Turabian StyleXiaoyin Liu; Junzeng Xu; Xinyi Zhou; Weiguang Wang; Shihong Yang. 2019. "Evaporative fraction and its application in estimating daily evapotranspiration of water-saving irrigated rice field." Journal of Hydrology 584, no. : 124317.
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.
Junzeng Xu; Yuping Lv; Xiaoyin Liu; Qi Wei; Zhiming Qi; Shihong Yang; Linxian Liao. A general non-rectangular hyperbola equation for photosynthetic light response curve of rice at various leaf ages. Scientific Reports 2019, 9, 1 -8.
AMA StyleJunzeng Xu, Yuping Lv, Xiaoyin Liu, Qi Wei, Zhiming Qi, Shihong Yang, Linxian Liao. A general non-rectangular hyperbola equation for photosynthetic light response curve of rice at various leaf ages. Scientific Reports. 2019; 9 (1):1-8.
Chicago/Turabian StyleJunzeng Xu; Yuping Lv; Xiaoyin Liu; Qi Wei; Zhiming Qi; Shihong Yang; Linxian Liao. 2019. "A general non-rectangular hyperbola equation for photosynthetic light response curve of rice at various leaf ages." Scientific Reports 9, no. 1: 1-8.