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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.