Crop Yield,soil Carbon Pool And Economic Benefit Of Conservation Tillage System In The Loess Plateau Based On Multi-scale Analysis

Conservation tillage is an important measure for increasing the efficiency of water use of dryland farming systems,enhancing land fertility,and improving soil health and economic profitability.With the focus on key agronomic production/resilience aspects such as crop yield,water use efficiency,and changes in soil carbon pool;this project integrated traditional field-based studies with meta-analysis,simulation modeling,and economic analysis to reveal how conservation tillage practices improved the quality and efficiency of conservation tillage systems in the Loess Plateau region of China.The research of relevant processes and mechanisms associated with conservation tillage is of important theoretical and practical significance for the wide application of this measure.Thus,the study first used extensive literature review and meta-quantitative analysis to synthesize the yield effects,water use characteristics,and changes in organic carbon pools of major crops under conservation tillage implemented in the Loess Plateau.Secondly,through 11 a longterm position observation,this manuscript systematically investigated the influences of traditional tillage(T),traditional tillage combined followed by straw mulching(TS),no-tillage(NT)and notill followed by straw mulching(NTS)on the crop yield,water use efficiency,and comprehensive economic efficiency of many predominant cropping systems that involve maize(Zea mays L.),winter wheat(Triticum aestivum L.)and soybean(Glycine max L.)in rotation.Additionally,support vector machine(SVM)modeling was used to simulate the crop yield and water use efficiency affected by different ecophysiological and managerial factors a cropping system level.The main findings were as follows:1.The meta-analysis on the experimental results of conservation tillage practices revealed that treatment T increased wheat yield by 9.7 and 14.3% compared with TS and NTS,respectively(P <0.05).Pea(Pisum sativum L.)yield was increased by 29.5% under treatment TS than T or NTS(P <0.05),while soybean yield was decreased by 7% under NT treatment(P <0.05)compared with T.Water use efficiency of maize under TS treatment increased by 12%,water use efficiency of wheat under TS and NTS treatments increased by 8.3 and 11.6% than T,respectively(P<0.05).Likewise,water use efficiency of pea increased by 10.8 and 20.7%,respectively(P <0.05).Interestingly,water use efficiency of soybean was decreased(P >0.05)under NT treatment than T.In terms of soil organic carbon content,the surface(0-10 cm)soil under TS and NTS treatments had 11.7 and 20.2% greater organic carbon than T,respectively(P <0.05),no increase in organic carbon content under NT treatment was found(P >0.05).2.The results of long-term position study showed that crop yield and above-ground biomass of TS-treated corn were 5.5,13.1,and 7.8% greater than those under T,NT,and NTS treatments,respectively(P <0.05).There were no significant differences in grain yield,straw yield,and above-ground biomass of winter wheat under T,TS,and NTS treatments.However,these indicators under TS treatment were significantly greater than those under NT treatment by 11.4,12.7,and 12.2%,respectively.Straw mulching significantly increased crop yield and above-ground biomass of soybean.Crop water use efficiency of under tillage treatments was significantly greater than that under no-tillage treatment.The SVM-based simulation modeling indicated great accuracy in estimating crop yield,with R2 values of 0.83,0.76 and 0.56 for winter wheat,corn and soybean,respectively;and in predicting water use efficiency,with R2 values of 0.84,0.71 and 0.68,respectively.The measured results were consistent with the prediction of the model.This model identified the main driving factors that could affect crop yield and water use efficiency and provided a basis for analyzing the mechanism of water conservation and yield increase of conservation tillage and evaluating the adaptability of the conservation tillage system under different environmental conditions in the future.3.The long-term position experiment showed that total organic carbon content in all layers of soil under NTS,TS and NT treatments increased significantly compared with T and this trend was particularly evident in the surface layer(P <0.05).Carbon pool index and carbon pool management index of 0-200 cm soil layer were the highest under NTS treatment.The benefits of long-term carbon sequestration showed that the annual carbon sequestration capacity in the tillage layer(0-30 cm)under NTS treatment was(CO2)29.55 t/hm2.According to the average transaction price of the carbon trading market in Beijing in 2016,the annual average benefits of carbon sequestration of farmland under NTS treatment was 1483 yuan/hm2.4.Energy analysis results showed that in the corn-wheat wheat-soybean rotation system,the total energy input,total energy output and net energy value under TS treatment were the highest,which were 194.9 GJ/hm2,377.42 GJ/hm2 and 329.07 GJ/hm2,respectively.Net energy value of TS was greater than those under T,NT,and NTS treatments by 6.4%,9.1%,and 1.0%,respectively.The economic benefit analysis results showed that the annual average input and output under TS processing were the greatest,which were 11,019 yuan/hm2 and 21,563 yuan/hm2 respectively.The annual average net revenue under NTS treatment was 5,952 yuan/hm2,which was greater than the 4,711 yuan/hm2 under T treatment,5,272 yuan/hm2 under TS treatment and 5,144 yuan/hm2 under NT treatment.In summary,the implementation of conservation tillage in the Loess Plateau region can significantly increase crop yield,improve water use efficiency and enhance soil carbon sequestration capacity;and it also has great economic and agroecological,thus,should be promoted in this region.