Effects Of Living Common Vetch And Rape Retention On Decomposition,Subsequent Wheat Yield And Soil C N

Green manure is an important material to improve the fertility of the soil and increase the yield of subsequent crops.The decomposition and nutrient release of organic matter affect the nutrient absorption of subsequent crops and the changes of soil nutrients,and the way of returning to the field greatly affects the decomposition of green manure.Planting forage crops in the summer fallow period is one of the ways to improve the utilization of water and heat resources in the winter wheat planting system of the Loess Plateau.However,planting forage crops in dry years leads to the reduction of subsequent winter wheat production due to the consumption of soil water,which is not conducive to the sustainable development of the system.Returning forage crops directly to the field is one of the effective measures to improve the climate resilience and comprehensive benefits of the rotation system.Therefore,this study was conducted to study the decomposition dynamics of common vetch（Vicia sativa）and rape（Brassica napus）under mulching（G）and overturning（B）into the field by using the nylon mesh bag method and to determine the yield of subsequent winter wheat（Trticum aestivums）and soil carbon and nitrogen nutrients.It provides a theoretical guidance for the utilization of green manure in the summer fallow period of winter wheat production system in semi-arid areas.The main results are as follows:（1）During the whole growth period of winter wheat,the cumulative decomposition rates of common vetch and rape were 65.2%and 71.9%,respectively,which were 51.1%and 36.8%higher than those under ground mulching（P<0.05）.The decomposition rates of common vetch and rape were 0.08 g·d^-1 and 0.09 g·d^-1,respectively,which were 1.6 and 1.25 times higher than those under ground mulching（P<0.05）.Under ground mulching,the highest carbon（C）degradation rate of common vetch was 16.5%,and the lowest C/N ratio was 13.96;the highest nitrogen（N）degradation rate and C/N ratio of rape were 35.5%and 20.55,respectively.（2）The leaf area index（LAI）and normalized difference vegetation index（NDVI）of winter wheat at filling stage under common vetch returning were higher than those of continuous winter wheat cropping（CW）.The LAI and NDVI values under common vetch ground mulching treatment were the largest,with an average of 3.81and 0.81,respectively.The grain yield of winter wheat under common vetch ground mulched（VG）and common vetch buried（VB）treatment were 4.85 t·hm^-2 and 4.60t·hm^-2,respectively,which was 14.8%and 8.1%higher than that of CW（P>0.05）,and the harvest index（HI）were 0.35 and 0.37,respectively.The LAI and NDVI of winter wheat after rape ground mulched were lower than those of CW.The grain yield of winter wheat after rape ground mulched（RG）and rape buried（RB）were 3.96 and3.89 t·hm^-2,respectively,and both HI was 0.36,which was not significantly different from CW yield（P>0.05）.（3）Compared with CW,the 0-25 cm soil water content under VG,VB,RG and RB treatments increased by 2.0%,5.0%,7.7%and 4.4%,respectively,and decreased by 16.8%,14.3%,12.1%and 14.8%compared with fallow（F）treatment.The contents of soil organic carbon（SOC）and total nitrogen（TN）under RB treatment were the highest,which were 9.72 g·kg^-1 and 1.06 g·kg^-1,respectively,which were22.1%,17.4%and 9.0%and 11.2%higher than those under F and CW treatments,respectively.Returning green manure significantly increased the contents of soil readily oxidized organic carbon（EOC）,nitrate nitrogen（NO₃^--N）and microbial biomass carbon and nitrogen（MBC and MBN）（P<0.05）.The contents of soil NO₃^--N,MBC and MBN under VG treatment were the highest,which were 39.7%,10.8%and2.8%higher than those under CW treatment,respectively.The soil EOC content under RG treatment was the highest,which were 75.8%and 9.7%higher than that of F and CW,respectively.Returning green manure significantly increased soil carbon and nitrogen invertase（P<0.05）.The activity ofβ-N-acetylglucosaminidase（NAG）in VG treatment was the highest,which was 3.63 nmol·g^-1·h^-1,which was 9.6%～14.2%higher than that in other treatments.The activities ofβ-1,4-glucosidase（βG）,Cellobiohydrolase（CBH）,β-Xylosidase（βX）and Leucineaminopeptidase（LAP）in returning rape treatments were higher than those in returning common vetch treatments.The activities ofβG,CBH,βX and LAP were 37.85,9.02,18.41 and390.40 nmol·g^-1·h^-1 under RG treatment,and 38.74,9.04,16.54 and 358.47nmol·g^-1·h^-1 under RB treatment,respectively.MBC and soil water content were the main factors affecting the activity of carbon and nitrogen invertase（P<0.001）.In summary,returning common vetch and rape in the Longdong Loess Plateau does not affect the grain yield of subsequent winter wheat,and burying green manure is more conducive to the improvement of soil carbon and nitrogen content.The results have theoretical and practical guiding significance for promoting the quality of regional farmland and high yield and quality of grain production.