| Straw return is one of the most important agricultural measures to achieve sustainable agricultural development,especially in dry agricultural areas where water is scarce and soils are poor.Straw return not only can change soil hydrothermal status,but also can affect soil ecological properties such as soil enzyme and soil microbial activities,which in turn affects soil fertility and crop yield.However,previous studies have lacked a systematic understanding of soil properties and crop productivity in agroecosystems under different straw return practices and their potential linkages.Therefore,it is important to explore the effects of different straw return methods on soil properties and crop productivity to optimize straw management strategies and maximize the straw return benefits.A meta-analysis was firstly used in this study,and a database of soil properties and yield under straw return was set at the global scale.This meta-analysis combined model selection and random forest approaches,taking into account multiple drivers including linear and non-linear relationships,to analyse changes in soil properties and the potential mechanisms and interactions between these variables and environmental factors under straw return in global agroecosystems.The effects of straw return on soil properties were quantified and the key factors affecting these parameters were evaluated.The field experiment was further analysed and guided based on this meta-analysis.Winter wheat(Triticum aestivum L.)was the test crop in Guanzhong Plain.Different straw return methods(no straw return(CK,control treatment),straw mulch(SM),straw incorporation(SI)and ammoniated straw incorporation(ASI))were explored to evaluated the effects on soil properties and yield as well as their potential links.This study aims to seek the optimal straw return with high crop yield and soil quality and provide theoretical basis.The main results are as follows:(1)A global database was set on soil properties and grain yield under straw return,and the effects of straw return on these parameters were evaluated.Straw return increased soil extracellular enzyme activity by 25%,soil dissolved organic carbon by 27%,soil easily oxidizable carbon by 24%,soil light fraction organic carbon by51%,soil particulate organic carbon by 34%,soil microbial biomass carbon(MBC)content by 31% and soil organic carbon(SOC)stock by 20%,respectively,relative to the CK treatment(p < 0.05).The positive effect of straw return on soil extracellular enzyme activity could be predicted by straw management practices(straw mulch and straw incorporation).The increase in soil microbial biomass carbon content and soil organic carbon content by straw return was positively correlated with changes in soil extracellular enzyme activity.In addition,the increase in soil carbon content due to straw return was influenced by environmental conditions(precipitation and air temperature)and soil properties(e.g.,soil p H and soil texture).The results clarified the understanding of the effect of straw return on soil enzyme activities and its role in improving soil properties,especially soil carbon pools,and establish a theoretical basis for increasing crop yields under straw return.(2)The effects of different straw return methods on soil hydrothermal status and soil biological properties were clarified.During the 2018-2019 and 2019-2020 winter wheat growing seasons,compared to the CK treatment,the SM,SI and ASI treatments significantly improved soil hydrothermal status.At the 0-10 cm and 10-20 cm soil layers,soil temperature showed a similar pattern,i.e.,soil temperature tended to increase,then decrease and finally increase.The SM,SI and ASI treatments significantly increased soil water storage,in relative to the CK treatment.Additionally,at the third stage of winter wheat,compared to the CK treatment,the SM,SI and ASI treatments significantly increased soil sucrase activity by 17%,24% and 22%,soil urease activity by 15%,21% and 14%,soil alkaline phosphatase activity by 14%,23% and20%,and soil catalase activity by 18%,24% and 21% at 0-10 cm soil depth,respectively(p< 0.05).These results suggest that it is feasible to improve soil hydrothermal status while obtaining higher soil enzyme activities by optimising straw return practices in Guanzhong Plain.(3)The effects of different straw return methods on soil physicochemical properties were clarified in Guanzhong Plain.Compared to the CK treatment,the SM,SI and ASI treatments significantly increased soil mean weight diameter(MWD)by 24%,22% and 27%,respectively(p < 0.05).During the 2018-2019 and 2019-2020 winter wheat growing seasons,the SM,SI and ASI treatments significantly increased soil organic carbon(SOC)content within the > 2 mm soil aggregates by 9%,18% and 24%,respectively,relative to the CK treatment(p < 0.05).The SM,SI and ASI treatments not only significantly increased soil saturated hydraulic conductivity,but also significantly improved soil water retention capacity.At the 0-10 cm and 10-20 cm soil depths,the SM,SI and ASI treatments significantly increased soil organic carbon(SOC)content and soil total nitrogen(TN)content over two consecutive winter wheat growing seasons(p < 0.05).The ASI treatment significantly increased the soil microbial mass carbon(MBC)content at 10-20 cm compared to the CK,SM and SI treatments(p < 0.05).However,the SM,SI and ASI treatments had no significant effect on the soil available phosphorus and potassium contents.In conclusion,straw return improved soil structure and increased soil SOC content,which in turn contributed to improved soil quality and higher crop yields.The results highlighted the effect of straw return on soil physicochemical properties and its positive role in improving soil structure and quality in dryland agriculture in Guanzhong Plain.(4)The effects of different straw return methods on winter wheat yield were clarified and potential linkages between soil properties and yield were explored.Compared to the CK,SM and SI treatments,the ASI treatment significantly increased wheat yield by 17%,13% and 10% respectively(p < 0.05).Similarly,the ASI treatment significantly increased aboveground biomass and 1000-grain weight of winter wheat.Linear mixed-effects model analysis showed that treatments(CK,SM,SI and ASI)had significant effects on aboveground biomass,effective spike number and 1000-grain weight of winter wheat(2018-2019 and 2019-2020 winter wheat growing seasons,p < 0.05).In addition,there was a positive correlation between changes in winter wheat yield and SOC and TN content.In this study,the treatment ranking for winter wheat yield and soil quality under different straw return methods was ASI > SI > SM > CK.Therefore,it is feasible to optimise straw return measures to achieve high winter wheat yields while improving soil fertility in the dryland agricultural region of the Guanzhong Plain. |
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