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【Background】 Soil microorganisms underpin soil functions, and its community is influenced by a multitude of abiotic and biotic factors. The objective of this paper is to study the combined effect of biochar amendment and subsurface drainage on microbial communities in salinized soil in coastal ecosystems. 【Method】 The experiment was conducted in a field at the Yellow River delta, with the subsurface drains spaced by10 m (S10), 20 m (S20), and 30 m (S30), respectively. For each drain spacing, there was a biochar amendment treatment and non-biochar treatment. During the experiment, we measured the changes in soil physicochemical properties and microbial community structure. And the main driving factors for the changes in microbial community structure under synergistic effect of biochar and subsurface drainage were elucidated. 【Result】 Biochar amendment and subsurface drainage altered soil physicochemical properties. Biochar amendment and drain spacing were interactive having a significant impact on salinity, nitrate nitrogen, organic matter and total phosphorus in the soil. The sequencing of AccuITSTM and Accu16STM showed that drain spacing working separately or in combination with biochar amendment had a significant effect on Agaricomycetes and Acidobacteria_Gp4, albeit the underlying mechanisms are elusive. Redundancy analysis and Pearson correlation analysis showed that the absolute abundance of Agaricomycetes and Mortierellomycetes, beneficial for crop growth, were negatively correlated with soil salinity and sodium ions while positively correlated with organic matter and nitrate nitrogen, both at significant levels. Sodium ion content was the key factor affecting soil bacteria and fungi in all treatments we compared. 【Conclusion】 Amending the salinized soil by biochar coupled with subsurface drainage with the drains spaced 10 m apart worked best for improving soil nutrient and soil microbial community structure. It can be used as an improved technique for soil reclamation and agriculture production in salinized soils in coastal regions.

【Objective】 The purpose of this paper is to give full play to the respective advantages and synergistic effects of straw mulching and suitable irrigation on crop yield and soil carbon sequestration and emission reduction, establish an efficient farmland management mode of emission reduction, increase, and water saving. 【Method】 Taking summer maize in Western Henan as the research object, the mulching method and the lower limit of irrigation water were tested. The mulching method was straw mulching (S) and no mulching (N). The lower limit of irrigation water was set at four levels: 50% (W1), 60% (W2), 70% (W3) and 80% (W4) of field water holding capacity. Soil respiration, crop biomass and grain yield under different treatments were systematically studied. The total amount of soil carbon emission, the amount of soil microbial isooxygen respiration carbon release and the amount of carbon sequestration of farmland net primary productivity were calculated. Farmland net ecosystem productivity (NEP) was calculated as the carbon sequestration of farmland net primary productivity and the carbon release of soil microbial iso-respiration. Carbon emission efficiency (CE) calculated from crop yields and soil carbon emissions reflected the economic and environmental benefits of farmland. NEP and CE were used to objectively evaluate the effects of straw mulching and different irrigation lower limits on crop yield and carbon sequestration. 【Result】 The soil respiration rate of SW4 treatment was the highest and that of NW1 treatment was the lowest. Soil respiration rate of SW4 treatment reached the highest value at anthesis stage 6.08 μmol/(m2·s), and there was no significant difference between SW3 treatment and NW4 treatment. Compared with NW1 treatment, straw mulching and irrigation increased the amount of carbon sequestration in farmland net primary productivity and the amount of soil microbial iso-respiratory carbon release, and that of SW4 treatment was the highest, with no significant difference compared with SW3 treatment and NW4 treatment. SW3 treatment had the highest NEP which was 3.99%-245.74% higher than that of other treatments and the highest CE which were 2.35%-138.80% higher than that of other treatments. Compared with SW4 treatment, NEP of SW3 treatment increased by 2.99% and CE of SW3 treatment increased by 2.35% under the premise of saving irrigation. 【Conclusion】 The lower limit of irrigation water is 70%FC and straw mulching (SW3) treatment, which can effectively coordinate the yield and carbon emission efficiency of summer maize farmland system, promote higher crop yield, achieve higher net ecosystem productivity and carbon emission efficiency, and reduce the carbon emission generated in the production process under the condition of higher irrigation amount. Achieve carbon sequestration and emission reduction and water utilization system promotion. Considering net ecosystem productivity and carbon emission efficiency of farmland, SW3 treatment can be used as a farmland management mode for water saving, emission reduction and yield increase.

【Background and objective】 Soil salinization is a biotic stress facing agriculture production in almost all countries. It not only destroys soil structure but also reduces bioavailable nutrients and the ability of soil to sequester carbon. Amending stalinized soil with biochar is a technology to improve soil quality and productivity, but its efficacy depends on soil texture and the amount of biochar being applied. The objective of this paper is to study the optimal biochar amendment for improving soil quality and fertility for cotton growth. 【Method】 The experiment was conducted in pots with the cultivar Medium S9612 used as the model plant. The soil was amended by biochar at ratios of 0 (CK), 1% (BC1), 1%(BC1), 3% (BC3) and 5% (BC5), respectively. In each treatment, we measured physicochemical properties, enzyme activities of the soil, as well as growth indexes of the cotton at seedling stage. 【Result】 Biochar amendment improved moisture content in the 0~20 cm soil layer, but the increase was negatively correlated with biochar amount; biochar also reduced salt content in the 0~20 cm soil layer. The amendment did not show significant effect on soil pH, total phosphorus, and available phosphorus, but increased soil organic carbon, total nitrogen, total potassium, available potassium, peroxidase (POD), and fibro two glycosidases (FTG), especially BC1 which significantly increased the activity of POD and FTG. In general, biochar reduced soil alkali-hydrolyzable nitrogen and polyphenol oxidase (PPO). BC1 increased stem diameter and above-ground dry matter accumulation of the crop, both significantly, but did not show noticeable impact on plant height. BC3 did not show significant effects on plant height, stem thickness, and above-ground dry matter, while BC5 reduced plant height, stem diameter, and above-ground dry matter. Also, addition of biochar reduced the total nitrogen content in stems and leaves. 【Conclusion】 Biochar can improve soil nutrients and enzyme activities but only when applied at an appropriate ratio. For the saline soil we studied, the optimal biochar amendment was 1%.

【Objective】 Waterlogging is a common abiotic stress affecting crop growth and soil functions. The purpose of this paper is to experimentally investigate short-term effect of waterlogging on mineral nitrogen and ammonia-oxidizing microorganisms in the rhizosphere and bulk soil of winter wheat. 【Method】 Waterlogging was imposed at the anthesis stage, and lasted 0 days, 3 days and 5 days, respectively. In each treatment, we measured the mineral nitrogen and the copy numbers of ammonia oxidizing microorganisms in the soil at the end of surface waterlogging, the end of subsurface waterlogging, as well as two days after the waterlogging completely eased. 【Result】 Compared with the control (without waterlogging), prolonged surface waterlogging promoted ammonium nitrogen and reduced nitrate nitrogen in both the rhizosphere and the bulk soil (P

【Objective】 Soil problems in southern Xinjiang of China are many and vary, characterized by scarce rainfall, shallow groundwater and high soil salinity. To safeguard crop production, mulched drip irrigation coupled with subsurface drain have been developed as the dominant cultivation in this region. The purpose of this paper is to experimentally study the efficacy of this system in desalinizing cotton fields. 【Method】 A two-year experiment was carried out in a cotton field with shallow groundwater table. Spacing of the subsurface drains varied from 10 m to 30 m, and their buried depth varied from 0.8 m to 1.1 m. Treatment without drains was taken as the control (CK). The field was mulched, and the cottons were drip-irrigated. The effect of the drains on spatiotemporal dynamics of soil salt was measured, and its variation in response to irrigation amounts was analyzed. 【Result】 A lack of drainage system resulted in inter- and intra-annual salt accumulation in the soil surface; installing subsurface drains reduced salt accumulation, with the reduction increasing significantly with the decrease in drain spacing and increase in their burying depth. Irrigation amount did not show a noticeable impact on salt leaching when the drains were absent, while having the drains in place increased the leaching rate by 10%~30%. Significance analysis of the desalination rate of the irrigation showed that salt leaching rate increased significantly with the decrease in drain spacing and the increase in drain depth. Regression analysis found that the desalination rate was impacted by drain spacing more than by the drain depth. The difference in soil salt content before and after the irrigation can be fitted to a leaching curve with R2 > 0.90. Using this curve, we calculated the irrigation amount required to leach salt in the 0~60 cm of soil below a critical value, which can be used to design the subsurface drainage system 【Conclusion】 The optimal design parameters for the areas we studied were: drain spacing 10 m, and drain depth 0.8 m. This can meet the requirement by keeping the salt content in the cotton field below a critical value.

【Background and objective】 Most agriculture-induced eco-environmental problems in north China are due to poor management in irrigation and fertigation of winter wheat, especially the use of nitrogen (N) fertilizer. Uptake of N by the wheat and its associated use efficiency depend on many biotic and abiotic factors, and the aim of this paper is to experimentally investigate how to improve them by optimally combining irrigation and fertigation at the jointing stage. 【Method】 The experiment was carried out in a field. It compared three irrigations: rain-fed (W1), irrigating 60 mm (W2), and 90 mm (W3) of water. For each irrigation treatment, there were three nitrogen top-dressing treatments: 0 kg/hm2 (N1), 75 kg/hm2 (N2) and 150 kg/hm2 (N3). The basal nitrogen application in all treatments was 150 kg/hm2. In each treatment, we measured the physiological traits, yield and N uptake of the crop. 【Result】 The leaf area index (LAI), plant height, aboveground biomass, grain yield and N uptake all increased significantly as the irrigation and nitrogen applications increased. However, when N top-dressing exceeded 75 kg/hm2, a further increase in N application did not have a significant effect on physiological traits of the crop, especially in W3 irrigation treatment. Grain yield was negatively correlated to the 1 000-grain weight at significant level; LAI, plant height, aboveground dry matter, grain numbers per spike, panicle numbers per spike were all positively correlated to the grain yield at significant level. With the increase in irrigation amount at the jointing stage, N production efficiency, grain N absorption and N utilization efficiency all increased, while the WUE decreased. With the increase in N top-dressing amount, N production efficiency, as well as grain N absorption and N utilization efficiency decreased, while the associated WUE increased. W3+N2 significantly increased grain yield and N uptake by 1.33%~65.92% and 4.63%~59.25%, respectively, compared with other treatments. 【Conclusion】 Considering crop growth and yield, as well as N uptake and N utilization efficiency, W3+N2 was the optimal irrigation and fertigation, achieving high yield while in the meantime reducing N application and increasing uptake and utilization efficiency of N by the crop.

【Objective】 Crops often endure various biotic and abiotic stresses during their growth. This paper investigates how thermal and waterlogging stresses occurring at booting stage affect photosynthesis and the ultimate yield of paddy field rice. 【Method】 The experiments were conducted in pots and consisted of four treatments: waterlogging stress by keeping the water on the soil surface 15 cm deep (T1), higher them stress (T2), high thermal stress combined with the waterlogging stress (T3). Conventional irrigation with water on the soil surface kept at 0~5 cm deep was taken as the control (CK). In each treatment, we measured the change in SPAD, photosynthetic traits and yield of the rice. 【Result】 Compared to CK, T2 reduced the photosynthetic rate by 30.77%, while T3 increased SPAD, photosynthetic rate and stomatal conductance of the leaves by up to 51.90%. Compared to CK, the impact of the stresses occurring at booting stage on shoot growth lasted into mature stage. It hence reduced the yield, especially T2 and T3 which reduced the rice yield by 80.09% and 12.33%, and 1 000-grain weight by 16.31% and 11.86% respectively. 【Conclusion】 To alleviate the adverse impact of thermal stress at the booting stage on yield, water in the soil surface should be kept about 15 cm deep to ameliorate the potential thermal damage.

As living standards rise, enhancing quality has become a central objective for many researchers. Soilless cultivation, known for its efficient use of resources, is increasingly used in vegetable production. It is critical to develop effective water and fertilizer management strategies to achieve high-quality yields and promote sustainable development in modern agriculture. This study employed an orthogonal experimental design to assess the impact of varying nutrient solution concentrations (50%, 75%, 100%, and 125% of Hoagland's), lower irrigation thresholds (40%, 55%, 70%, and 85% field capacity (FC)), and ozone concentrations (0, 1, 2, and 4 mg·L−1) on lettuce growth, yield, quality, and water–fertilizer use efficiency. The results indicated that fixed nutrient solution concentrations and lower irrigation thresholds enhanced growth metrics for lettuce. Similarly, increasing ozone concentrations initially improved, then reduced growth metrics when the lower irrigation threshold was constant. Furthermore, maintaining stable ozone concentrations while raising the nutrient solution concentration initially boosted, then diminished, growth indicators. Optimal conditions for water and fertilizer management were identified at a nutrient solution concentration of 75% to 100% and an ozone concentration of 0 to 1 mg·L−1. Variance analysis highlighted the significant effects of nutrient solution concentration, lower irrigation thresholds, and ozone concentrations on lettuce yield, quality, and water and fertilizer use efficiency. Range analysis revealed the optimal management combination to be a nutrient solution concentration of 100%, an 85% lower FC irrigation threshold, and an ozone concentration of 1 mg·L−1, yielding 16.82 t·ha−1 of lettuce and a water use efficiency of 40.14 kg·m−3. These findings provide theoretical support for the sustainable advancement of soilless cultivation in contemporary agriculture. [ABSTRACT FROM AUTHOR]

The rice waterlogging stress test was conducted at the experimental base of the College of Agriculture, Yangtze University, using Yangxian You 418 as the test subject, in order to investigate the impact of waterlogging on rice growth during the period from July to August each year. Six waterlogging stress tests with different waterlogging depth (1/4 plant height (1/4PH), 2/4 PH, and 3/4 PH) and duration (5 d and 7 d) were set up at the jointing–booting stage of rice (T1: 1/4 PH, 7 d; T2: 2/4 PH, 7 d; T3: 3/4 PH, 7 d; T4: 1/4 PH, 5 d; T5: 2/4 PH, 5 d; T6: 3/4 PH, 5 d;) with shallow water irrigation (CK) as control. The plant height, population leaf area, above-ground dry matter, and the yield of rice were measured. The correlation between the waterlogging depth and rice yield reduction was analyzed, and the flood disaster threshold index of rice was established. The results showed that at the end of stress, the plant height of all waterlogged treatments exceeded CK, and the plant height of T3 and T6 treatments significantly increased by 31.90% and 15.93%, respectively. The leaf area of rice treated with T1, T3, T4, and T5 was higher than CK (p < 0.05), and the above-ground dry matter of rice treated with T2, T3, T4, T5, and T6 was higher than CK (p < 0.05). When normal irrigation was restored to the maturity stage, the plant height of all rice treated with waterlogging was still higher than CK (p < 0.05). However, as the degree of waterlogging increased, rice yield decreased significantly, with a notable reduction of 31.68% observed in the T3 treatment compared to CK. Assuming a drainage index based on a 20% decrease in rice yield, it is imperative that the ratio of flooded depth to plant height remains below 37% when waterlogging persists for 7 days in rice cultivation. These research findings offer crucial scientific insights for implementing effective drainage management measures during flood disasters in rice paddies. [ABSTRACT FROM AUTHOR]

Applying biochar to saline soil is a novel strategy for improving soil quality. However, how biochar addition amount affects soil nutrients, bacterial communities, and cotton growth at different stages remains unclear. Three biochar treatments, no biochar (BC0), 1% biochar (BC1, w/w), 3% biochar (BC3), and two cotton varieties, salt‐sensitive (SS) and salt‐tolerant (ST), were used in pot experiments, analyzing biochar effects on saline soil nutrients, bacterial communities, and cotton growth. The study found that biochar increased only organic carbon (SOC), total nitrogen (TN), and available potassium (AK) at the seedling stage. However, at the flowering‐boll stage, biochar also increased nitrate (NO3−–N) and available phosphorus (AP) and reduced soil salt content. Biochar did not affect α‐diversity at the seedling stage, but BC3 reduced α‐diversity at the flowering‐boll stage. The principal coordinate analysis revealed changes in the soil bacterial community composition that were closely associated with biochar added. From the redundancy analyses, SOC and AK were the leading environmental factors for soil bacterial community composition changes. SOC, TN, and AK correlated positively with Proteobacteria, which increased their relative abundance through biochar addition and correlated negatively with Bacteroidetes, Chloroflexi, and Acidobacteria, which decreased their relative abundance due to biochar. Furthermore, the random forests analysis showed that SOC, Shannon index, and β‐diversity were significant predictors of cotton biomass. In summary, biochar drives changes in bacterial communities in saline soils by increasing nutrients such as SOC and AK, which affect cotton growth. This study provides data to support the application of biochar on saline soils. [ABSTRACT FROM AUTHOR]

Soil CO2 and CH4 concentrations are crucial determinants of crop physiology and the soil environment. However, the intricate relationships among soil respiration, soil nutrients, enzyme activities, and winter wheat growth in the presence of shallow groundwater remain enigmatic. This study aimed to investigate the dynamics of soil CO2 and CH4 concentrations and their correlations with soil nutrient content, enzymatic activities, and wheat root biomass to better understand the influence of shallow groundwater on soil environmental conditions. Lysimeter experiments were conducted at five groundwater depths (20, 40, 50, 60, and 80 cm) and three fertilizer application rates (low, 75%; normal, 100%; high, 125%). Soil CO2 (soil layer > 10 cm) and CH4 concentrations significantly decreased with increasing groundwater depth. The maximum values of root parameters and shoot biomass were mainly concentrated at 50–60 cm at the high fertilization level (except root length density, which was higher at the normal fertilization level), and were 0.36–77.4% higher than other treatments. Soil CO2 concentration showed positive correlations with organic matter and total N content, enzyme activities, and root biomass. Soil CH4 concentration had significant correlations with soil organic matter, total N, and available K. Compared to the fertilization level, groundwater depth emerged as a crucial factor as it affected soil physicochemical properties, soil enzymatic activities, root respiration, and winter wheat growth in shallow groundwater. [ABSTRACT FROM AUTHOR]

The impacts of rhizosphere microorganisms on the turnover of nutrients are affected by many environmental factors. In this study, rice plants were subjected to deep flooding and heat stress for one week at the jointing stage. Rhizospheric soil was sampled for the analysis of rice rhizosphere bacterial assembly and functional groups responsible for carbon and nitrogen transformation. Compared with the control, both deep flooding and heat stress increased bacterial alpha diversity. Moreover, heat stress and the interactions of heat stress and deep flooding improved the bacterial cooperation. Heat stress reduced the relative abundance of Actinobacteria and Firmicutes, which are responsible for organic carbon decomposition. The relative abundance of the gene encoding lignin-degrading catalases under deep flooding and heat stress treatments reduced by 6% and 8%, respectively. The interaction of heat stress and deep flooding increased the relative abundance of the nifD gene by 5%, may slowed down nitrate reduction to nitrite. Our results highlight the effects of heat and flooding stress on the bacteria-mediated mechanisms responsible for regulating organic carbon sequestration and nitrogen cycling in rhizosphere of paddy fields. [ABSTRACT FROM AUTHOR]

Waterlogging and salinization are considered to be the main threats to agricultural productivity and land resources in coastal areas of China. Thus far, drainage and field soil improvement programs have been ineffective. In this article, we investigated the effect of subsurface drainage combined with biochar (B–S) on soil physicochemical properties and soil bacterial community structure in coastal saline soil. In this study, B–S significantly reduced soil electrical conductivity (EC) and soil water content (W) by 35% and 10.65% compared to no drainage (CK). Compared to CK and drainage alone (S), B–S significantly increased soil total nitrogen (TN) by 24.78% and 39.62%, soil available phosphorus (AP) by 28.29% and 69.82%, soil nitrate (NO3−-N) by 64.65% and 35.45%, and significantly increased soil organic matter (SOM) by 74.69% and 66.10%, respectively. It also significantly increased alkaline phosphatase (ALP) and urease activities. The results of redundancy analysis (RDA) showed that CAT and urease made the greatest response to changes in environmental factors, indicating that CAT is more sensitive to changes in environmental alterations than ALP. AP was the dominant factor in the change in enzyme activity (R2 = 53.0%, p < 0.05), followed by NO3−-N (R2 = 14.8%). SOM was the dominant factor in the variation in microbial abundance content (R2 = 38.5%, p < 0.05), followed by ALP (R2 = 20.0%, p < 0.05). The results of the study can provide guidance for effective land use and sustainable development of agricultural soil ecology in coastal areas. [ABSTRACT FROM AUTHOR]

Exploring the impact of subsurface drainage on microbial community structures in saline-alkali soils is of great significance for maintaining the sustainability of saline-alkali fields. In this study, seven field treatments were designed in cotton fields: two drain depth (0.8 and 1.1 m) and three drain spacing (10, 20, and 30 m) treatments, as well as no drainage (control). Soil samples were obtained in the seedling and flowering and boll-setting (FBS) stages, and the soil properties and microbial communities (bacteria and fungi) were analyzed. The results displayed that compared with the control group, soil salt was significantly decreased in all subsurface drainage treatments. Subsurface drainage treatments have no effect on microbial richness and diversity. Both drain depth and spacing had significant effects on bacterial and fungal composition structures in the seedling stage, but only drain depth significantly altered soil microbial composition structures in the FBS stage. Based on the null model, the assembly of soil microbial communities was mainly driven by stochastic processes. The contributions of the deterministic process for soil bacterial community assembly at the seedling stage and FBS stage were 18.1% and 22.1%, respectively. In contrast, soil fungal community assembly was mainly determined by dispersal limitation and drift. [ABSTRACT FROM AUTHOR]

Stomatal regulation plays a pivotal role in the adaption of plants to different water conditions. In order to understand characteristics of stomatal resistance of crops with different irrigation methods, differences in leaf stomatal resistance and contribution of stomatal aperture to water vapor transfer were investigated with a field experiment conducted under alternative deficit water supply and under conventional furrow irrigation. Results indicated that for individual maize leaf, regardless of irrigation methods, the stomatal resistance decreased gradually from the base to the tip of the maize leaf. At the population level, the stomatal resistance of maize leaf increased gradually from canopy top to bottom. For the change of the leaf stomatal resistance in time, diurnal variation of leaf stomatal resistance was in a W shape. Diurnal and daily changes in the leaf stomatal resistance in the upper canopy were relatively small. The upper surface of maize leaf contributed more to CO2 and water vapor transfer than the ones underside. Except at the seedling stage, the leaves in the upper and middle part of maize canopy contributed more than 80% of the total CO2 and water vapor. Stomatal resistances of maize leaves decreased with the increase in leaf age during the vegetative growth stage. Differences in stomatal resistance among maize leaves of different ages were increased by the alternative deficit water supply. During the reproductive growth phase, leaf age had no significant influence on the stomatal resistance in matured leaves. Compared with the conventional furrow irrigation with sufficient water supply, the alternative deficit water supply increased the ratio of the stomatal resistances between the upper side and underside of maize leaves. The vertical gradient of stomatal resistance from canopy top to bottom increased significantly (P<0.05), decreasing leaf stomatal conductivity rapidly, and improving the contribution of the stomatal aperture in the upper canopy to water vapor transfer. Therefore, the leaf stomatal resistance of maize was regulated by furrow irrigation methods and soil water condition, and it was affected by the leaf age, leaf area index and natural feature of stomatal aperture. The study is useful for controllable irrigation technology and water vapor cycle in soil plant atmosphere continuum (SPAC). [ABSTRACT FROM AUTHOR]