| The objective of this research was to determine a suitable tillage rotations and organic manure practices in wheat-maize cropping system of North China Plain which can not only enhance the carbon sequestration capacity,promote nutrient accumulation,but also improve crop yield and economic benefits.Six treatments were compared,which were straw returning with rotary tillage-subsoiling(PRS),straw returning with subsoiling-no tillage(PSN),straw returning with conventional tillage-no tillage(PCN),cow manure with rotary tillagesubsoiling(FRS),cow manure with subsoiling-no tillage(FSN),and cow manure with conventional tillage-no tillage(FCN).This study evaluated the effects of tillage rotation,organic manure practices and their interactions on soil organic carbon fractions,nutrient content,enzyme activity and crop yields,as well as the correlation between soil enzyme activity and organic carbon fractions,nutrient content.The main results were as follows:1 Effects of organic manure and tillage rotation practices on labile organic carbon fractionsThe tillage rotation,organic manure and their interactions significant affected soil organic carbon and its fractions(SOC,MBC,ROOC,POC).At wheat and maize harvest,the RS and SN patterns had higher contents of soil organic carbon and its labile fractions in 0-10 cm and 10-20 cm soil layers compared with the CN pattern.Under the same tillage rotation patterns,compared with the return of straw,the application of cow manure resulted in significantly higher soil readily oxidized organic carbon and particulate organic carbon at wheat harvest.The soil organic carbon contents and its labile fractions were the highest in the FSN treatment among the six treatments.The organic carbon content in 20-30 cm and 30-40 cm soil layers reached the maximum at the flowering stage of maize.2.Effects of organic manure and tillage rotation practices on soil nutrientsThe tillage rotation,organic manure and their interactions significant affected total nitrogen,available phosphorus,available potassium.At wheat and maize harvest,the RS and SN patterns had higher contents of total nitrogen,available phosphorus and available potassium in 0-10 cm and 10-20 cm soil layers compared with the CN pattern.At maize harvest in 2016,compared with the RS,SN patterns,the CN pattern significantly increased soil total nitrogen contents in 20-30 cm soil layer by 12.23%-26.20%,10.89%-13.67% respectively.Compared with the RS,SN patterns,the CN pattern significantly increased soil available potassium contents in 30-40 cm soil layer by 1.88%-16.04%,2.82%-24.24% respectively.Compared with the return of straw,the application of cow manure significantly increased the available phosphorus content in 0-10 cm soil layer at wheat and maize harvest.The return of straw significantly increased the available potassium content in each soil layer at maize harvest compared with the application of cow manure.In 0-10 cm and 10-20 cm soil layers,the interaction of cow manure and subsoiling-no tillage significantly increased the total nitrogen and available phosphorus contents;However,the contents of available potassium significantly increased in response to interaction of cow manure and rotary tillage-subsoiling.Whether in wheat or maize growing period,the content of available potassium reached the maximum at flowering stage in 0-10 cm and 10-20 cm soil layers.For the content of available phosphorus,each treatment reached the maximum at wheat jointing stage;for total nitrogen content,each treatment was the lowest at maize jointing stage.3 Effects of organic manure and tillage rotation practices on soil enzyme activitiesThe tillage rotation,organic manure and their interactions significant affected invertase,urease and catalase activities.At wheat and maize harvest,the RS and SN patterns had higher contents of invertase and urease activities in 0-10 cm and 10-20 cm soil layers compared with the CN pattern.In 20-30 cm and 30-40 cm soil layers,the RS pattern had higher contents of catalase activities compared with the SN,CN patterns at maize harvest;The SN pattern had higher contents of catalase activities compared with the RS,CN patterns at wheat harvest.Compared with the return of straw,the application of cow manure significantly increased the invertase activity of wheat harvest in 10-20 cm,20-30 cm soil layers,and also significantly increased the urease activity of maize harvest in each soil layer.In the 0-10 cm and 10-20 cm soil layers.The interaction of cow manure and subsoiling-no-tillage was the most significant increased soil activity of invertase,urease and catalase.4 Effects of organic manure and tillage rotation practices on crop yields and economic benefitsThe tillage rotation,organic manure and their interactions significant affected crop yield.The costs of SN and CN patterns were the same,but the SN pattern was significantly increased annual yield and income by 4.53%-9.43%,2.15%-11.82% respectively compared with CN pattern.The costs of applying cow manure was higher than that of straw returning directly to the field,but the application of cow manure significantly increased the annual yield and benefit under the SN and CN patterns compared with the return of straw.The costs of cow manure combined with subsoiling-no-tillage was not only lower than that of rotary tillage-subsoiling,but also significantly increased the yield and income by 5.05%-5.58%,9.07%-11.17%,respectively.5 Carbon footprints under different organic manure and tillage rotation practices in a wheat-maize crop systemIn wheat period,the difference of rotation tillage and organic manure treatments of carbon footprint was mainly caused by the difference of carbon emissions from application chemical fertilizer and tillage methods.The proportion of carbon footprint produced by application chemical fertilizer was the largest.In maize period,the difference of rotation tillage and organic manure treatments of carbon footprint was mainly caused by the difference of tillage methods.The proportion of carbon footprint produced by application chemical fertilizer was the largest.The carbon cost of FSN treatment was lowest in a wheat-maize crop system.This indicated that the interaction of cow manure and subsoiling-no tillage not only had low input-output ratio,but also emitted less carbon in the production process,which was conducive to soil carbon sequestration.6 Correlation analysis between soil organic carbon fractions,nutrients,enzyme activity and crop yieldSoil total nitrogen was positively correlated with organic carbon and its fractions.Available phosphorus was positively correlated with organic carbon,readily oxidized organic carbon and particulate organic carbon.Available potassium was positively correlated with organic carbon and readily oxidized organic carbon.Soil organic carbon and total nitrogen were positively correlated with sucrase,urease and catalase.Microbial biomass carbon and particulate organic carbon were mainly affected by sucrase.Readily oxidizable organic carbon and available phosphorus were mainly affected by sucrase and catalase.Available potassium was mainly affected by urease and catalase.Crop yield was mainly affected by carbon footprint,total nitrogen and microbial biomass carbon.Compared with other treatments,the FSN treatment has significant advantages in improving carbon sequestration capacity,nutrient content,enzyme activity and increasing both crop yields and economic benefits,although requires a larger economic input at the early stage.Thus,the FSN management practice is a good method for increasing soil quality and crop productivity and is expected to be adopted in the wheat-maize cropping systems of the North China Plain. |
PDF Full Text Request