| Dry land accounts for more than 60% of China’s arable land.The Loess Plateau regions are the typical dryland and rain-fed agricultural areas,and water shortage and poor soil fertility limit crop production in this area.Conservation tillage can improve precipitation storage efficiency and soil quality,thereby increasing soil productivity.To determine the effects of different fertilization modeand conservation tillage on the grain yield,soil water,soil fertility,soil microbial and the relationship between microbial and soil fertility,A 7-year(2014-2020)field experiment was conducted in Fuping Modern Agriculture Comprehensive Experimental Station in Weibei,Shaanxi Province.Also,the DSSAT model was used to verify and simulate the yield of winter wheat and spring corn and also the soil water content.The fertilization mode include NP、NPK、manure input(M)and NPM,tillage mode include straw mulching(NPS),film mulching(NPF),bare furrow and ridge(NPR),plastic film-mulched ridge and straw-mulched furrow(NPRFS)and green manure(NPG).The major objective of this study was to improve soil water content and nutrients managements,reveal the importance of microbial community structure and diversity to soil quality improvement,provide a theoretical basis for the sustainable development of dryland agriculture.The main results were as follows:(1)Different conservation tillage mode had the different effect on soil moisture,precipitation storage efficiency and grain yield.Plastic film-mulched ridge and straw-mulched furrow(NPRFS)was the best measure to increase grain yield in dryland.This measure integrated the plastic film mulching to the soil water storage and straw mulching improved the soil fertility,so water and fertility together improve the yield.For wheat,the average yield for NPRFS from 2015-2020 was 8.2%-63.6% higher than other treatments,and it was 6.4%-77.5% for maize.NPRFS couldreduce the ineffective evaporation of soil water during fallow period and increase the effective water consumption during the growth period.The order of water consumption during the fallow period was NP>CK>NPF>NPS>NPRFS.The precipitation use efficiency(PUE)was improved under NPRFS,for wheat,the PUE for NPRFS increased by 5.2%-67.6% compared with other treatments,and it was increased by 30.1%-60.7% for maize.From the perspective of nutrients,NPRFS can reduce the accumulation of nitrate in soil profile,which is more beneficial to crop nutrient absorption,reduce nitrogen residue,improve fertilizer utilization rate and increase crop yield.(2)Different fertilization treatments also had different effects on soil moisture,nutrient and crop yield.Among them,the yield of NPM was the highest.The yield of wheat increased by 0.19%-24.4% compared with other treatments,and increased by 2.7%-40.4%for maize.For WUE,NPM treatment increased by 5.7%-23.1% for wheat and 0.6%-45.1%for maize,respectively.At the same time,NPM reduced the accumulation of soil nitrate nitrogen,and nitrogen use efficiency(NUE)increased by 53.6% in wheat and 121.8% in maize from 2015 to 2020 compared with NP,which increased soil organic matter content and increased crop yield.The above results were also verified by the DSSAT model,which can better simulate the growth and yield of crops and dynamic changes of soil moisture except in dry years,and guide the optimization management of local crop production and fertilization.(3)Planting green manure in dryland could consume soil water storage in fallow period,and had different effects on crop yield with different rainfall years.In normal rainfall or abundant rainfall years,the water deficit caused by green manure will be replenished.Long-term planting of green manure increased the content of soil organic matter,available nitrogen and available phosphorus,therefore,had a positive effect on crop yield.For winter wheat,planting green manure increased organic matter by 2.0%-31.8% and 16.5%-25.3% for available N compared with NP from 2016-2020.For maize,organic matter content was increased by 3.8%-4.6% and 42.3%-87.8% for available N compared with NP from2016-2020.Crop yields were severely reduced in insufficient rainfall years.The effect of green manure on yield was mainly affected by annual rainfall,growth period rainfall and precipitation storage efficiency.(4)Long-term fertilization resulted in soil nutrient surplus.For winter wheat,the accumulated nitrate increased about 37 kg/ha when N balance content in soil was increased at each 100 kg/ha.The available P increased about 1.7 mg/kg when P balance in soil was increased at each 100 kg/ha.For maize,the accumulated nitrate increased about 45 kg/ha when N balance in soil was increased at each 100 kg/ha.The available P increased about2.3mg/kg when P balance in soil was increased at each 100 kg/ha.Potassiumfertilizer can improve grain yields,which indicating that the deficit and accumulation of available nutrients in soil was mainly determined by the nutrient balances in soil.(5)Fertilization and conservation tillage had different positive effect on soil aggregates,organic carbon and enzyme activity.M、NPK and NPM increased organic carbon content by48.2%,3.7% and 26.9% compared with NP.The order of mean weight diameter(MWD)was M>NPM>NPK>NP> CK.NPM increased the stability of soil aggregates.At the same time,organic fertilizer input improved activity of sucrase,phosphatase and urease.Compared with NP,soil organic carbon content of straw mulching(NPS),plastic film-mulched ridge and straw-mulched furrow(NPRFS),green manure(NPG)increased by 44.6%、23.1% and11.4%.It also increased >7mm aggregates and the activities of sucrase and phosphatase,but had no significant difference in catalase.(6)By detecting OTU numbers and analyzing the alpha diversity,the highest bacterial and fungal community diversity was NPM,and the community diversity order was NPM>NPK>NPG>CK.As shown by the beta diversity,there were significant differences in bacterial and fungal communities between treatments.RDA analysis showed that soil physical and chemical properties had a significant effect on microbial community structure.For bacteria,soil organic matter,total N and available P were the most important driving factors.For fungi,p H,available N and organic matter were the main driving factors.Therefore,manure input and conservation tillage can improve microbial diversity,changed the microbial community distribution,and provided a possible way for sustainable agricultural management.In conclusion,the mechanism ofconservation tillage and combined application of organic and inorganic fertilizers to increase crop yield is that this measuressignificantly increase theprecipitation storage efficiency,improve soil organic carbon and expand soil carbon pool,and also improve microbial community structure and diversity. |
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