| Climate change is one of the main challenges faced by peoples globally and it induced a serious threat to agriculture industry.Greenhouse gas emissions are chief contributor to climate change,nevertheless cultivated soils are prominent source of greenhouse gas emissions.Moreover,in semi-arid region,the most of cultivated soils have low organic matter due to climatic limitations that affect crop yields,yet this multifaceted challenge can be alleviated and mitigated through agricultural management strategies.Conservation tillage was often used to improve soil physicochemical and microbial properties and reduce greenhouse gas emissions and mitigate climate change and improve agricultural sustainability.Despite extensive literature on conservation agriculture as an approach to increase soil and water conservation,resilience and mitigation agroecosystems capacity,there is still scarcity of information on the influences of different conservation tillage practices on soil physical,chemical and biological properties particularly at different soil depths,yield and greenhouse gas emissions under spring-wheat agroecosystems on a semi-arid sandy-loam cropland particularly at Dingxi in China.Hence,this study was conducted in Longzhong dryland production area from 2019 to2021,different tillage strategies(viz.conventional tillage(CT)control,straw incorporation with conventional tillage(CTS),no tillage(NT)and stubble-return with no tillage(NTS)were laid under randomized complete block design with three replications to examine their impacts on soil properties,wheat yield and greenhouse gas emissions on a semi-arid sandy-loam cropland,in order to provide a theoretical basis for greenhouse gas emission reduction in wheat fields in semi-arid areas.The main conclusions are shown below:(1)Soil physical properties viz.bulk density,pore space,gravimetric soil water content,soil water storage,water filled pore space,soil aggregates,saturated hydraulic conductivity and soil temperature were significantly influenced by different tillage systems.Significant reduction was observed under conservation tillage practices(viz.NTS,CTS and NT)over CT in case of soil bulk density at 0-10 cm,10-20 cm and 20-40 cm soil depths.The NTS,CTS and NT significantly increased gravimetric soil water content,soil water storage,water filled pore space,soil aggregates and saturated hydraulic conductivity compared with CT during the three years of study period at different soil depths.Moreover,conservation tillage systems significantly decreased average soil temperature over CT.The soil temperature followed the trend of CT > CTS > NT > NTS.(2)The NTS,CTS,and NT significantly increased soil organic carbon,light fraction organic carbon,carbon storage,total nitrogen,available nitrogen,nitrogen storage,total phosphorous,available phosphorous,total potassium and available potassium over CT.In 0-10 cm,10-20 cm and 20-40 cm soil depths during the three years of study period,the soil chemical properties followed the trend of NTS > CTS > NT > CT.Moreover,the influence of conservation tillage systems was reduced with increasing soil depth particularly at 10-20 cm and 20-40 cm soil depths in case of soil p H,electrical conductivity,C:N ratio,N:P ratio and C:P ratio.The general distribution of soil nutrients at 0-10 cm,10-20 cm and 20-40 cm soil depths with regard to conservation tillage systems was greater over conventional tillage,based on Principal Component Analysis.(3)Significantly higher soil biological properties were recorded under NTS,NT and CTS over CT at different soil depths.At 0-10 cm soil depth,the NTS,NT and CTS treatments notably increased the soil microbial counts by 28,20 and 14% respectively,soil urease activity by 8,6 and 3% respectively,soil alkaline phosphatase activity by 25,22 and 16% respectively,soil invertase activity by 24,15 and 8% respectively,soil cellulase activity by 6,5 and 3% and soil catalase activity by 5,3 and 2% respectively compared with CT average over three years study period.At 10-20 cm and 20-40 cm soil depths,the soil biological properties followed the trend of NTS > NT > CTS > CT.Moreover,the microbial biomasses(carbon and nitrogen)were highest under conservation tillage practices over CT.The microbial biomasses(carbon and nitrogen)were in order of CT < NT < CTS < NTS.(4)Conservation tillage practices viz.NTS,CTS and NT significantly(P < 0.05)increased wheat yield.Average across three years study,the NTS,CTS and NT treatments increased aboveground biomass yield by 40,25 and 12% respectively whilst grain yield increased by 16,11 and 7% respectively compared with CT.Overall,wheat agronomic traits viz.plant height,number of spikes per plant,number of seeds per meter square,root yield,thousand seed weight and dry matter yield were higher under NTS,CTS and NT over CT.The agronomic traits followed the trend of CT < NT < CTS < NTS.(5)Significant variations were observed in greenhouse gas fluxes under different conservation tillage practices.Average carbon dioxide flux rates followed the order: NTS <NT < CTS < CT.The NTS and NT reduced carbon dioxide emissions by 35 and 29 %respectively over CT system across three years.The methane absorption under NTS,NT and CTS practices was markedly higher over CT technique.Significantly higher methane absorption was noted under NTS system whilst CT system had lowest methane absorption rates during the three years of study period.Significantly reduction of nitrous oxide emission was recorded under NTS,NT and CTS compared with CT system.Moreover,NTS and NT practices resulted in noteworthy decrease in net global warming potential over CT systems.Carbon dioxide,methane and nitrous oxide emissions had significant positive correlation with soil temperature,water content and bulk density whilst carbon dioxide,methane and nitrous oxide emissions had negative correlation with soil hydraulic conductivity,organic carbon and light fraction organic carbon.In summary,implementation of conservation tillage systems for instance stubbleretention,residue incorporation and no tillage on a semi-arid sandy-loam crop land can increase spring-wheat yield by improving soil physical,chemical and biological properties.Especially,the no tillage with stubble-retention technique can increase soil and environmental quality as a result of decreased greenhouse gas emissions.Therefore,conservation tillage could be recommended as a tillage practice in regional farmland that can improve soil properties,yield and environmental sustainability. |
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