Comparison of five Boosting-based models for estimating daily reference evapotranspiration with limited meteorological variables.

Accurate ET0 estimation is of great significance in effective agricultural water management and realizing future intelligent irrigation. This study compares the performance of five Boosting-based models, including Adaptive Boosting(ADA), Gradient Boosting Decision Tree(GBDT), Extreme Gradient Boosting(XGB), Light Gradient Boosting Decision Machine(LGB) and Gradient boosting with categorical features support(CAT), for estimating daily ET0 across 10 stations in the eastern monsoon zone of China. Six different input combinations and 10-fold cross validation method were considered for fully evaluating model accuracy and stability under the condition of limited meteorological variables input. Meanwhile, path analysis was used to analyze the effect of meteorological variables on daily ET0 and their contribution to the estimation results. The results indicated that CAT models could achieve the highest accuracy (with global average RMSE of 0.5667 mm d-1, MAE of 4199 mm d-1and Adj_R2 of 0.8514) and best stability regardless of input combination and stations. Among the inputted meteorological variables, solar radiation(Rs) offers the largest contribution (with average value of 0.7703) to the R2 value of the estimation results and its direct effect on ET0 increases (ranging 0.8654 to 0.9090) as the station's latitude goes down, while maximum temperature (Tmax) showes the contrary trend (ranging from 0.8598 to 0.5268). These results could help to optimize and simplify the variables contained in input combinations. The comparison between models based on the number of the day in a year (J) and extraterrestrial radiation (Ra) manifested that both J and Ra could improve the modeling accuracy and the improvement increased with the station's latitudes. However, models with J could achieve better accuracy than those with Ra. In conclusion, CAT models can be most recommended for estimating ET0 and input variable J can be promoted to improve model performance with limited meteorological variables in the eastern monsoon zone of China

Improvement of Photosynthesis by Biochar and Vermicompost to Enhance Tomato (<i>Solanum lycopersicum</i> L.) Yield under Greenhouse Conditions

Chlorophyll fluorescence is an important tool in the study of photosynthesis and its effect on the physiological indicators of crop growth is worth exploring. The trial was conducted to investigate the effect of biochar (CK, 0%; BA3, 3%; BA5, 5%; by mass of soil) and vermicompost (VA3, 3%; VA5, 5%) on photosynthesis, chlorophyll fluorescence, and tomato yield under greenhouse condition. Results revealed that photosynthetic parameters and chlorophyll fluorescence traits of BA3, VA3, BA5, and VA5 were significantly higher than those of CK, and the improvement of vermicompost was more effective than biochar at the same application rate. VA3 treatment had the highest net photosynthetic rate (Pn), intercellular CO2 concentration (Ci), variable fluorescence (Fv), maximum fluorescence (Fm), PSII maximum photochemical efficiency (Fv/Fm), PSII potential photochemical activity (Fv/Fo), absorption flux per cross section (CS; ABC/CSm), trapped energy flux per CS (TRo/CSm), and electron transport flux per CS (ETo/CSm), which increased by 49%, 65%, 17%, 12%, 4%, 25%, 10%, 15%, and 30%, respectively, compared with CK. The study also found that BA and VA rates could effectively improve tomato yield and water use efficiency (WUE). The yield under BA3, VA3, BA5, and VA5 treatments was 21%, 33%, 23%, and 25% higher than that under CK, and the WUE increased from 31.2 kg·m−3 under CK to 41.4 kg·m−3 under VA3. Pearson correlation analysis indicated that the increment of photosynthesis showed a highly significant correlation with Fv/Fo, ABC/CSm, TRo/CSm, and ETo/CSm and enhanced the light energy absorbed, trapped, and transported per CS of plant leaves, thereby contributing to the increase in tomato yield. Therefore, for one-season tomato production, the application of 3% vermicompost was considered economical with regard to improving photosynthesis, enhancing WUE, and increasing tomato yield

Response of Photosynthesis in Wheat (<i>Triticum aestivum</i> L.) Cultivars to Moderate Heat Stress at Meiosis and Anthesis Stages

High temperature has seriously impacted the production of wheat in many countries. We examined four wheat cultivars (PBW343, Berkurt, Janz, and Attila) under heat stress (35/25 °C) and control treatments (23/15 °C) for 3 days at the meiosis and anthesis stages to evaluate the response and recovery of the four cultivars to heat stress and the relationship between photosynthetic parameters related to heat tolerance. Photosynthetic activity in all cultivars declined in plants that were treated at 35 °C, even for only 1 d compared with control plants. However, the differences among the four cultivars were obvious in net photosynthetic rate (Pn). At meiosis, the reduction of Pn in Berkut and PBW343 was lower and could nearly fully recover after 3 d of recovery and showed higher heat tolerance characteristics. The highest reduction in Pn occurred in Janz, which did not recover completely after 3 d of recovery. The same trend was observed at the anthesis stage, but Pn in all cultivars could not fully recover. Taking transpiration rate (Tr), stomatal conductance (gs), intercellular CO2 concentration (Ci), and limitation of stomatal conductance (Ls) into account, results suggested the decline in Pn under heat stress was mainly caused by non-stomatal restriction. In parallel with the decline in Pn, the maximum photochemical efficiency (Fv/Fm) decreased. In addition, both the maximum rate of net photosynthesis (Pmax) and the light saturation point declined after heat stress in all cultivars. However, the relevant photosynthetic parameters of PBW343 and Berkut recovered more quickly at both the meiotic and flowering stages. In summary, there were significant differences in the adaptability of different cultivars to high temperatures, with Berkut and PBW343 being more adaptable to heat stress than Janz and Attila. These may be used as valuable resources for further studies in breeding to understand the physiological mechanisms of heat sensitivity. This paper provides detailed information on the ecophysiological responses of wheat under heat stress

Modification of Soil Physical Properties by Maize Straw Biochar and Earthworm Manure to Enhance Hydraulic Characteristics under Greenhouse Condition

The deterioration of soil physical properties had led to a decrease in soil–water availability in facility agriculture. Thus, an experiment was set up with five soil treatments of 0% (CK, No additives), 3% biochar (BA3, Mass ratio), 3% earthworm manure (QA3), 5% biochar (BA5), and 5% earthworm manure (QA5) to investigate the effects on soil physical properties and hydraulic characteristics under greenhouse conditions. The physical properties of soil including the soil bulk density (BD) and total porosity (TP) were measured; the results showed that BA5 provided the lowest soil BD (1.24 g·cm−3) and the highest TP (53.09%) and was 13.8% higher than CK. More importantly, the saturated hydraulic conductivity (KS), field capacity (FC), permanent wilting point (PWP), and available water content (AWC) of the soils treated with biochar and earthworm manure were significantly higher than those of CK. At the same application rate, the effect of biochar on soil–water permeability and water-retention capacity was significantly higher than that of earthworm manure, in which the soil–water-characteristic curve (SWCC) showed that as BA5 > BA3 > QA5 > QA3 > CK, the FC and AWC increased from 28.90% and 14.13% under CK, respectively, to 40.73% and 21.91% under BA5, respectively; and the KS, FC, PWP and AWC of BA5 increased by 45.93%, 40.91%, 27.46% and 54.96% compared with CK, respectively. The results revealed that the improvement of the soil TP was conducive to the enhancement of the soil KS and FC, enhanced the soil–water permeability and the water-retention capacity, and ultimately increased the AWC. From the perspective of improving the facility soil and economic benefits, the application of 5% biochar is considered to be the most beneficial

Analytic Method for Optimizing the Allocation of Manure Nutrients Based on the Assessment of Land Carrying Capacity: A Case Study from a Typical Agricultural Region in China

The separation between planting and breeding results in an unbalanced distribution of the regional livestock and poultry manure (RLM) industry, and it has raised great concerns. A holistic analysis and problem-solving scheme using 72 townships as the research point was developed in this study. On the basis of a survey from a typical agricultural region in China, the local characteristics of manure discharge, land use, and crop cultivation were analyzed. The assessment of land carrying capacity and environmental risk assessment was conducted by simulating the nitrogen cycle. Afterwards, optimized livestock breeding strategies and inter-regional transfer and flow scheme of manure nutrients were proposed. The spatial distribution of RLM in terms of pig manure equivalent showed an imbalance of high north–south and low middle, and the nitrogen requirement of crops showed a decreasing trend from north to south. In some townships, the environmental risks were higher than level I, which indicated that pollution existed around large construction sites and water areas in the northwest. The land carrying capacity index calculated at 50% nutrient ratio displayed no overloaded risk, whereas 10–20% nutrient ratio exhibited overloaded risk. Assessments showed that the residual RLM and its nitrogen volume were 151,700 and 3574.64 tons per year, respectively. More than 80% of the study area could be used as a nitrogen nutrient sink area, and only six townships are nitrogen nutrient sources. Therefore, optimizing the allocation of manure nutrients is expected to avoid agricultural contamination from livestock manure

Environmental Assessment of Soils and Crops Based on Heavy Metal Risk Analysis in Southeastern China

Heavy metal pollution in soil–crop systems has attracted great attention globally, caused by rapid urbanization and intensive industrialization. The research aims to investigate the environmental quality of the agricultural production area in Taizhou City, a typical economic region that is along the Yangtze River in the Southeast of China. A total of 370 sampling sites were chosen, with 370 soil, rice (Oryza sativa L.) and wheat (Triticum aestivum L.) samples collected, respectively, for measuring and analyzing the status, spatial distribution and pollution level of different heavy metals. The mean values of soil Cr, Pb, Cd, As and Hg were 66.78, 32.88, 0.23, 8.16 and 0.16 mg/kg, which were lower than the risk control standard values (RCV). However, the mean values of Pb, Cd and Hg were 1.25-, 1.77- and 2-fold larger than their soil background values (SBV) due to the intensive anthropogenic activities. The average content of Cd in rice exceeded its food safety limiting values (FCV) by 0.05 mg/kg, and the average contents of Pb in rice and wheat both exceeded the relevant FSV by 0.42 and 0.186 mg/kg, respectively. In addition, the maximum As and Cr contents in rice and wheat could be 0.13, 0.46 mg/kg and 0.63, 3.5 mg/kg larger than the relative FCVs in certain areas. Most of the high-value areas of soil and crop heavy metals were mainly located in Xinghua City, Taixing City and Jiangyan District, which had a similar distribution pattern with local industries or anthropogenic activities. The heavy metal pollution in soils and crops was found to be inconsistent, as 8.94% of the arable land possessed lightly metal pollution, while 3.18% of the area of rice and 4.0% of the area of wheat suffered severe pollution, with excessive accumulation of Cr, Pb and Cd. Based on the heavy metal pollution assessment of soil–crop systems, approximately 83% of the study area possessed medium or higher environmental quality, which was preferable for agricultural production. Our results implied that the spatial distribution and pollution level of the heavy metals in soil–crop systems were significantly influenced by industrial activities, followed by agricultural sources, transportation emissions and so on. Therefore, continuous monitoring and source control of heavy metals, especially for Cr, Pb and Cd, should be conducted to ensure the regional environmental quality and food security

Wheat Straw Burial Enhances the Root Physiology, Productivity, and Water Utilization Efficiency of Rice under Alternative Wetting and Drying Irrigation

This study evaluated whether the straw burial and alternative wetting and drying (AWD) irrigation could improve the root activity, yield, and water utilization efficiency (WUE) of rice. Accordingly, we conducted a field experiment with three straw burial levels, i.e., with no straw burial (NSB), low straw burial 300 kg.ha−1 (LSB), and dense straw burial 800 kg.ha−1 (DSB), and three irrigation regimes, i.e., alternate wetting/moderate drying (AWMD), alternate wetting/severe drying (AWSD), and alternate wetting/critical drying (AWCD). Results showed that straw burial improved the root activity, rice yield, and WUE under AWD regimes. The combination AWMD×DSB resulted in the greatest values of total dry mass (1764.7 g/m2) and water use (853.1 mm). Conversely, the treatment AWCD × NSB led to the lowest values of total biomass (583.3 g/m2) and water use (321.8 mm). Root dry weight density (1.11 g cm−3) and root active absorption area (31.6 m2 plant−1) were higher in the treatment AWMD × DSB than root dry weight density (0.41 g cm−3) and root active absorption area (21.2 m2 plant−1) were in the treatment AWCD×NSB. The former combined treatment increased root oxidation ability (55.5 mg g−1 FWh−1), the root surface phosphatase activity (1.67 mg g−1 FWh−1) and nitrate reductase activity of root (14.4 μg g−1 h−1) while the latter considerably reduced the values of root oxidation ability (21.4 mg g−1 FWh−1), the root surface phosphatase activity (0.87 mg g−1 FWh−1) and nitrate reductase activity of root (5.8 μg g−1 h−1). The following conclusions can be drawn with regard to water use and biomass yield. (i) The reduction in water consumption was greater than the reduction in yield in the case of AWSD. (ii) The decline in water consumption was less than the decline in biomass yield in the case of AWCD. (iii) The increase in in water consumption was greater than the increase in biomass yield in the case of AWMD. Therefore, the indicators of WUE were recorded in the following order: AWSD > AWMD > AWCD. This study recommends AWD irrigation to improve the root growth traits that contribute to the greater biomass yield of rice. It also suggests that farmers should implement AWD irrigation after leaving wheat straw residues in the field, and followed by deep tillage, to mitigate the negative effect of drought stress caused by AWD irrigation, preserving plant growth without large biomass losses, and thus, addressing the constrains of straw residues and sustaining rice production under limited freshwater resources

Wheat Straw Burial Enhances the Root Physiology, Productivity, and Water Utilization Efficiency of Rice under Alternative Wetting and Drying Irrigation

This study evaluated whether the straw burial and alternative wetting and drying (AWD) irrigation could improve the root activity, yield, and water utilization efficiency (WUE) of rice. Accordingly, we conducted a field experiment with three straw burial levels, i.e., with no straw burial (NSB), low straw burial 300 kg.ha&minus;1 (LSB), and dense straw burial 800 kg.ha&minus;1 (DSB), and three irrigation regimes, i.e., alternate wetting/moderate drying (AWMD), alternate wetting/severe drying (AWSD), and alternate wetting/critical drying (AWCD). Results showed that straw burial improved the root activity, rice yield, and WUE under AWD regimes. The combination AWMD&times;DSB resulted in the greatest values of total dry mass (1764.7 g/m2) and water use (853.1 mm). Conversely, the treatment AWCD &times; NSB led to the lowest values of total biomass (583.3 g/m2) and water use (321.8 mm). Root dry weight density (1.11 g cm&minus;3) and root active absorption area (31.6 m2 plant&minus;1) were higher in the treatment AWMD &times; DSB than root dry weight density (0.41 g cm&minus;3) and root active absorption area (21.2 m2 plant&minus;1) were in the treatment AWCD&times;NSB. The former combined treatment increased root oxidation ability (55.5 mg g&minus;1 FWh&minus;1), the root surface phosphatase activity (1.67 mg g&minus;1 FWh&minus;1) and nitrate reductase activity of root (14.4 &mu;g g&minus;1 h&minus;1) while the latter considerably reduced the values of root oxidation ability (21.4 mg g&minus;1 FWh&minus;1), the root surface phosphatase activity (0.87 mg g&minus;1 FWh&minus;1) and nitrate reductase activity of root (5.8 &mu;g g&minus;1 h&minus;1). The following conclusions can be drawn with regard to water use and biomass yield. (i) The reduction in water consumption was greater than the reduction in yield in the case of AWSD. (ii) The decline in water consumption was less than the decline in biomass yield in the case of AWCD. (iii) The increase in in water consumption was greater than the increase in biomass yield in the case of AWMD. Therefore, the indicators of WUE were recorded in the following order: AWSD &gt; AWMD &gt; AWCD. This study recommends AWD irrigation to improve the root growth traits that contribute to the greater biomass yield of rice. It also suggests that farmers should implement AWD irrigation after leaving wheat straw residues in the field, and followed by deep tillage, to mitigate the negative effect of drought stress caused by AWD irrigation, preserving plant growth without large biomass losses, and thus, addressing the constrains of straw residues and sustaining rice production under limited freshwater resources

Subsurface Drip Irrigation with Emitters Placed at Suitable Depth Can Mitigate N2O Emissions and Enhance Chinese Cabbage Yield under Greenhouse Cultivation

Agricultural practices, such as applying excessive water and nitrogen fertilizer to increase the crop yield, can be a significant source of greenhouse gas emissions (GHGs). Therefore, techniques and proper management are needed to mitigate these emissions without yield reduction. The experiment used three subsurface drip irrigation (SDI) depths with emitters buried at 0.05, 0.10, and 0.15 m below the soil surface, along with two nitrogen fertilizer (Urea, N &gt; 46.2%) application levels of 300 kg N ha&minus;1 (N300) and 240 kg N ha&minus;1 (N240) to investigate the effect of vertical and horizontal water and fertilizer distribution on N2O emissions under different SDI techniques in greenhouse conditions. The results indicated that soil N2O emissions from SDI10 and SDI15 decreased by 7.06% and 10.69%, respectively, compared to SDI5. N2O, WFPS, NH4+-N, and NO3&minus;-N were significantly reduced with the increased radial distance from the emitter. N2O was positively correlated to WFPS and NH4+-N while negatively correlated to NO3&minus;-N. The NH4+-N and NO3&minus;-N concentrations decreased with depth and increased with fertilization events. Furthermore, N2O, WFPS, NH4+-N, and NO3&minus;-N were increased under N300 compared to N240 (p &gt; 0.05). The findings demonstrated that the Chinese cabbage yield was significantly enhanced under SDI15 compared to SDI5 and SDI10. Furthermore, N300 can increase the cabbage yield more than N240 among all treatments

A Comprehensive Review of the Multiple Uses of Water in Aquaculture-Integrated Agriculture Based on International and National Experiences

Multiple uses of water aquaculture-integrated agriculture systems (AIAS) are inevitable to produce more food per drop of water to address water shortage, food insecurity, and climate change. This survey intends to outline the multiple-use water in pond-based AIAS in light of legal regulations and water salinity. Scenarios for pond-based AIA and their impact on the environment were presented and discussed. Pond-based AIA has been demonstrated to have many social, economic, and environmental benefits. Moreover, international and national experiences and attempts for genuine applications were exhibited. Throughout, pond-based AIA farming practices are seen as a proficient utilization of water that aids food sustainability. It was concluded that pond-based AIA could aid in increasing productivity, income for food producers and soil fertility, ecosystem maintenance, and adaptation to environmental change. AIAS helps adapt to and mitigate climate change by reducing waste and greenhouse gas emissions, reducing pressure on water resources, and recycling nutrients. Finally, developing and promoting the expansion of rotation of wheat-fish and pond-based AIA in the desert and encouraging global collaboration for information and knowledge transfer among different countries were discussed