Effects Of Organic Amendments And No Tillage On Nematode Communities,Enzyme Activities And Crop Yields

Red soil agroecosystem has faced the challenge of the degradation of soil fertility and the loss of soil biodiversity as well as ecosystem functions.Soil nematodes are the most abundant microfauna,which have unique advantages in representing the structural and functional changes of soil food web following disturbance and restoration.Organic amendments and conservation management could re-use the organic wates as sustitutes of fertilizers,reduce the distruction of soil structure,so improving soil habitat and crop yields.This study has 8 treatments with a full-factorial 2x2x2 design(without and with straw amended;without and with pig manure;conventional tillage and no-tillages).The two consecutive years' investigation explored the effect of organic amendments and conservation management on nematode communities and ecosystem function,as well as the the relationship between soil environmental factors,nematode communities and function.The results are as follows:(1)No-tillage significantly increased soil bulk density while organic amendments decreased soil maximum water holding capacity and increased soil pH and nutrient content.Organic amendments and conservation tillage improved soil fertility and improve soil habitat.(2)Amendment of straw,pig manure and no-tillage had significant effects on soil basal respiration and microbial biomass,and there was a significant interaction among them.For example,the responses of basal respiration to organic amendement depended on tillage.Organic amendemtns increased microbial biomass regardless of tillage.(3)There are significant interactions in terms of sampling times,organic amendments and tillage.The organic amendment combining no-tillage increased total abundance of nematodes.Effects of different factors on nematode trophic groups were different.Bacterivores and fungivores increased with pig manure and straw respectively,and herbivores decreased under straw.Pig manure and straw increased nematode maturity index,shannon diversity,enrichment index and nematode channel ratio,suggesting that organic amendment was one of the most effective practice to assemble stable nematode community.(4)Soil nematode communities were distinctly separatedly by sampling times,Straw,pig manure and no-tillage treatments in non-metric multidimensional scaling(nMDS)ordination.(5)Organic amendments significantly increased crop yields and biomass,confirming that organic amendments improved soil habitat especially in July compared to November.Irrspective of tillage management,pig manure significantly increased enzyme activities involved in C,N and P cycling.Enzyme activities showed an increasing trend except for the drought November in 2016.Temperature and humidity are also important for crop growth and soil enzyme activity with favorable water and heat facilitatign crop growth and soil enzyme activities.(6)Redundancy analysis(RDA)showed a close relationship between soil nematode communities,physicochemical properties,microbial communities and soil ecosystem function.Our results supported the common point that nematodes are ideal bioindicators for soil ecosystem state.(7)Influences of sampling times were strong and even outweigh the organic amendments and tillage practices,especially for pH,water holding capacity,available nutrients.Soil basal respiration,microbial biomass,total nematodes and different nematode trophic groups increased with experiment duration,except for the drought November.