A Study On Consistent Effect Of Biochar Amendment On Crop Yield,Soil Properties And Greenhouse Gas Emissions In Agriculture

The conversion of crop straw and other organic wastes from agriculture to biochar,via pyrolysis,is becoming a new technique to utilize crop residues.If amended into agricultural soils,biochar could increase soil carbon sequestration and improve soil fertility and crop productivity.There is a growing interesting in biochar production and soil amendment,not only because it utilizes agricultural organic wastes and it also has great potential in soil fertility improvement and carbon sequestration.Although a lot of studies have shown that biochar can improve soil properties,enhance crop productivity and reduce the emission of greenhouse gases.These results are mostly from short-term experiments.Therefore,it is still unclear how biochar affect soil properties,crop productivity and GHGs emission in the long run and how long the effecs can persist.This study was conducted in a rice-winter wheat rotatioin system,which is located was the East part of Chengdu plain.The objective of this study was to access the changes in crop yield and nutrients uptake,soil properties and GHGs emission following a single biochar amendment at high application rates.We aimed to provide a scientific suggestion for the development of biochar use in agriculture.The field triap was started in 2010 with two factors including biochar application and nitrogen fertilization.Biochar was applied at application rate of 0,20 and 40 t·ha-1.Nitrogen fertilizer was applied at two rates including normal nitrogen fertilization(N1)and no nitrogen fertilization(NO).Therefore,there was six treatments in total and each treatment was replicated three times.Crop yield was monitored in rice season of 2014 and 2015 and wheat season in 2015.Nutrient uptake and soil properties were analized.Greenhouse gases(GHGs)emission was nomitored in rice season in 2014.The sustainable effect of biochar on crop yield,nutrient uptake,soil properties and GHGs emission was dicussed by putting the results at early stage after this experiment establishment.The main results are as follows:(1)Crop yield and nutrient uptake:Biochar amendment had no effect on the yield of rice grains and biomass of straw and root in 2014,but it increased wheat grain yield and straw biomass in 2015 respectively at rate of 40 t·ha-1 in the presence of nitrogen fertilizer and decreased rice grain yield in 2015 respectively in the absesence of nitrogen fertilizer.However,the effect of biochar nutrients uptake varied across plant parts and elements.More specifically,biochar decreased the concentration of N in rice straw while it had no effect on the concentration of N in rice grain.Biochar increased the uptake of P by rice straw in 2014 and decreased the uptake of P by rice grain,whereas a contrry effect was observed on rice.Biochar increased the uptake of K by rice in 2014 and wheat in 2015 while it decreased the uptake of K in rice straw and root in 2015.(2)Soil properties:Biochar amendment increased soil pH,organic carbon,total N,available P and available K but decreased the bulk density in rice in 2014 and 2015,wheat in 2015.The effect of biochar on soil microbial biomass was modified by nitrogen fertilization.In the absence of N fertilizer,biochar amendment had no effect on soil microbial biomass carbon and N(MNC and MBN),but it increased the MBC and MBN in the presence of nitrogen fertilizer.However,biochar amendment had no effect on soil dissolved organic carbon extracted by hot water with or without nitrogen fertilizer.(3)GHGs emission:Biochar had no effect on the emission of CH4,CO2,and N2O and this was not affected by N fertilization during rice growing season in 2014.In addition,no significant changed in GWP(CH4+N2O)and GHGI was observed.In conclusion,the effect of biochar,after a sinlge amendment in higher dose,on crop yield was modified by crop types,N fertilization and biochar amended years.During the early stage after biochar amendment,biochar has no significant effect on crop yield.However,biochar increased wheat yield and aboveground biomass significantly in the presense of N fertilizer after 5 years' application.The positive effect of biochar on soil pH,organic carbon,total N,available P and available K could persist at least for 5 years.However,the effect of GHGs mitigation disappeared after 5 years amendment.