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

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

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

Soil flushing coupled with aminated-nanocellulose/MOF hydrogel nanocomposites adsorbents : a novel sustainable remediation strategy for Cr (VI)-contaminated agricultural soils

Abstract: Soil flushing and adsorption-based soil remediation are promising options for removing heavy metals in agricultural soil. However, they encounter limitations in low removal efficiency, secondary pollution potential, or the need for a purification/recovery process. Optimizing flushing solutions or the functional properties of adsorbents could fundamentally eliminate the drawbacks of these methods. Yet, their practical application remains a formidable challenge. Herein, a new combined remediation strategy of multiple-pulse water soil flushing (MF) with novel aminated cellulose nanofibers (A-NFCs)/AEM/AM@MIL-100(Fe) nanocomposite hydrogel adsorbent (ANCMH) was adopted to remove Cr(VI) from agricultural soil. The characteristic analyses approved Cr(VI) adsorption-coupled reduction/swelling-based mechanisms on ANCMH with the maximum theoretical adsorption capacity of 338.24 mg g -1 at pH 6.8 governed by pseudo-second-order and Freundlich models. Instead of conventional MF application using environmentally problematic extractant fluids, a 5-day soil column simulation trial of MF coupled with ANCMH adsorbent layers (MF@ANCMH) was applied in medium-to-highly Cr(VI)contaminated soil followed by easy ANCMHs separation, preventing secondary pollution. Innovatively, the water flushing-stop flux events favorably decreased the pH of neutral soil by 0.83 folds and allowed Cr(VI) release from the soil matrix to be adsorbed by ANCMHs, achieving a high Cr(VI) removal efficiency of 98.9 %. Compared to the soil treated with ANCMH individually and soil flushed with water or Na 2 EDTA, the MF@ANCMH-treated soil reached the corresponding regulation of permissible levels for Cr(VI) residential scenarios in agricultural soil of 5.6 ppm with 3-cycles of ANCMH reuse. The residual Cr in MF@ANCMH-remediated soil displayed minimal bioavailability at root-zoon soil of <= 4.2 ppm and a 97.66 % reduction in its exchangeable-carbonate fraction compared to untreated soil, corresponding to a risk assessment code score below 1 %. Also, the application of MF@ANCMH resulted in Cr bioaccumulation below 0.1 ppm in cultivated wheat plants, prevented the physiological phytotoxicity symptoms, and elevated their antioxidant enzyme activity, photosynthesis, growth, and yielding indicators compared to that grown in untreated soil. Furthermore, it improved soil organic matter, microbial community, diversity, and microecological functions. This study provides a promising alternative remediation strategy for neutral soil that can maintain soil/crop quality and soil health with high chemical/ environmental stability of pollutants after remediation, demonstrating its sustainability and feasibility in agricultural soil

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

Soil Gaseous Carbon Emissions from Lettuce Fields as Influenced by Different Irrigation Lower Limits and Methods

Lettuce is a water-sensitive stem-used plant, and its rapid growth process causes significant disturbances to the soil. Few studies have focused on the gaseous carbon emissions from lettuce fields under different irrigation methods. Therefore, this study investigated the effect of different drip-irrigation lower limits and methods (drip and furrow irrigation) on greenhouse gas (CO2, CH4) emissions from lettuce fields. Thus, drip irrigation (DI) was implemented using three different lower limits of irrigation corresponding to 75%, 65%, and 55% of the field capacity, and named DR1, DR2, and DR3, respectively. Furrow irrigation (FI) was used as a control treatment. The CO2 and CH4 emission fluxes, soil temperature, and soil enzyme activities were detected. The results showed that the cumulative CO2 emission was highest under DR3 and relatively lower under DR1. For the FI treatment, the cumulative CO2 emission (382.7 g C m−2) was higher than that under DR1 but 20.2% lower than that under DR2. The cumulative CH4 emissions under FI (0.012 g C m−2) were the greatest in the whole lettuce growth period, while DR2 and DR3 treatments emitted lower amounts of CH4. The irrigation method considerably enhanced the activity of urease and catalase, meanwhile promoting CO2 emission. The low irrigation amount each time combined with high irrigation frequency reduced soil CO2 emission while increasing CH4 emission. From the perspective of the total reduction of gaseous carbon, DR1 is the optimal drip irrigation method among all the irrigation lower limits and methods

Interactive Effects of Microbial Fertilizer and Soil Salinity on the Hydraulic Properties of Salt-Affected Soil

Significant research has been conducted on the effects of fertilizers or agents on the sustainable development of agriculture in salinization areas. By contrast, limited consideration has been given to the interactive effects of microbial fertilizer (MF) and salinity on hydraulic properties in secondary salinization soil (SS) and coastal saline soil (CS). An incubation experiment was conducted to investigate the effects of saline soil types, salinity levels (non-saline, low-salinity, and high-salinity soils), and MF amounts (32.89 g kg−1 and 0 g kg−1) on soil hydraulic properties. Applied MF improved soil water holding capacity in each saline soil compared with that in CK, and SS was higher than CS. Applied MF increased saturated moisture, field capacity, capillary fracture moisture, the wilting coefficient, and the hygroscopic coefficient by 0.02–18.91% in SS, while it was increased by 11.62–181.88% in CS. It increased soil water supply capacity in SS (except for high-salinity soil) and CS by 0.02–14.53% and 0.04–2.34%, respectively, compared with that in CK. Soil available, readily available, and unavailable water were positively correlated with MF, while soil gravity and readily available and unavailable water were positively correlated with salinity in SS. Therefore, a potential fertilization program with MF should be developed to increase hydraulic properties or mitigate the adverse effects of salinity on plants in similar SS or CS areas

Optimization of a Lower Irrigation Limit for Lettuce Based on Comprehensive Evaluation: A Field Experiment

When optimizing irrigation methods, much consideration is given to crop growth indicators while less attention has been paid to soil’s gaseous carbon (C) and nitrogen (N) emission indicators. Therefore, adopting an irrigation practice that can reduce emissions while maintaining crop yield and quality is of great interest. Thus, open-field experiments were conducted from September 2020 to January 2022 using a single-factor randomized block design with three replications. The lettuce plants (“Feiqiao Lettuce No.1”) were grown using four different irrigation methods established by setting the lower limit of drip irrigation to 75%, 65%, and 55% of soil water content at field capacity corresponding to DR1, DR2, and DR3, respectively. Furrow irrigation (FI) was used as a control. Crop growth indicators and soil gas emissions were observed. Results showed that the mean lettuce yield under DR1 (64,500 kg/ha) was the highest, and it was lower under DR3 and FI. The lettuces under DR3 showed greater concentrations of crude fiber, vitamin C, and soluble sugar, and a greater nitrate concentration. Compared with FI, the DR treatments were more conducive to improving the comprehensive quality of lettuce, including the measured appearance and nutritional quality. Among all the irrigation methods, FI had the maximum cracking rate of lettuce, reaching 25.3%, 24.6%, and 22.7%, respectively, for the three continuous seasons. The stem cracking rates under DR2 were the lowest—only 10.1%, 14.4%, and 8.2%, respectively, which were decreased to nearly half compared with FI. The entropy model detected that the weight coefficient evaluation value of DR2 was the greatest, reaching 0.93, indicating that the DR2 method has the optimal benefits under comprehensive consideration of water saving, yield increase, quality improvement, and emission reduction