Effects Of Biochar On N And P Leaching In Yellow Soil And Growth Of Oil Peony In Karst Region

Yellow soil is the main soil type for agricultural production in Guizhou Province.Special karst geological conditions and abundant rainfall in Guizhou province often cause soil nutrients intensely leached,whitch results in not only poor soil fertility to limit to plant growth,but also degradation of water qunlity in rivers and lakes.Biochar can be used to improve soil environments and to control nutrient leached,and correspondingly carbon is sequestrated in the soil to reduce greenhouse gas emissions.However,it is still unclear for the following questions:what are effects of biochar application on the contents of nitrogen and phosphorus in yellow soil?How mchu is the decreases of nitrogen and phosphorus loss in runoff and leachate solution with the biochar applicaton to soils?How much is optimal biochar amount?To unserstand these,we used a combination method of indoor soil column simulating leaching and field tests to study the effect of biochar addition on changes of nutrient contents in soils,nitrogen and phosphorus loss with leaching solution and surface runoff in yellow soil,and the growth of oil peony under biochar application.The main results are as follows:(1)In indoor simulation test,soil pH,soil total nitrogen,available nitrogen,soil total phosphorus,and available phosphorus all increased with the increasing of biochar addition to soil.The volume of cumulative leaching solutions was decreased with the increasing of biochar addition compared to the control,when the amount of biochar added to soil was 2kg/m~2,4 kg/m~2,6 kg/m~2,respectively.The volume of cumulative leaching solutions was decreased by 0.3%,1.5%,and 2.0%,respectively compared with controls.Total phosphorus,total nitrogen,nitrate nitrogen,and ammonia nitrogen in the leaching solution from soil were also reduced significantly with incrasing addition of biochar.The addition of 2 kg/m~2 was the best for control of nutrient leaching loss among these treatments,followed by 4 kg/m~2.The addition of biochar can effectively reduce the leaching of nutrients in yellow soil and maintain soil fertility.(2)Under natural rainfall conditions,adding biochar to yellow soil in farmland could reduce surface runoff and nitrogen and phosphorus loss with the surface runoff from farmland.In the event of torrential rain,the addition of biochar caused the increasing loss of total phosphorus,and comparatively the addition of 4 kg/m~2 was the lowest loss for total phosphorus among all treatments.The concentration of total nitrogen in surface runoff with 2kg/m~2 of biochar added to soil was reduced 9.78%compared with the control treatment.Ammonia-nitrogen concentration in surface runoff with the addition of 4 kg/m~2 decreased by11.39%;Nitrate concentration in surface runoff at 6 kg/m~2 of adding level was reduced by18.45%.In the event of heavy rain,total phosphorus concentration in the surface runoff with4kg/m~2 of adding level was reduced by 26.67%compared with control,Total nitrogen concentration in the surface runoff with 2kg/m~2 of adding level was reduced by 12.94%;The concentration of ammonia nitrogen in surface runoff with 4kg/m~2 of adding level was reduced by 13.11%.The concentration of nitrate in surface runoff at 6 kg/m~2 of adding level was reduced by 7.81%.In the event of moderate rain,total phosphorus concentration in surface runoff with 6 kg/m~2 of the addition level was reduced by 21.88%compared with control.Total nitrogen concentration in surface runoff with 4 kg/m~2 of the additing level was reduced by 19.65%.Ammonia-nitrogen concentration in surface runoff with 4 kg/m~2 of the addition level decreased 20.33%.The concentration of nitrate in surface runoff at 6 kg/m~2 of the addition level was reduced by 12.11%.However,there is a significant difference of total nitrogen concentration only between 6 kg/m~2 and 4 kg/m~2 of the addition level in the event of moderate rain.Adding 4 kg/m~2 of biochar to soil showed better effects on reduction of total phosphorus,total nitrogen and ammonia nitrogen loss with surface runoff than other treatments.Comparatively,addition of 6kg/m~2 biochar to soil showed better effects on reduction of nitrate nitrogen loss with surface runoff than other treatments.(3)The addition of biochar to soil under fertilization conditions had a significant effect on the growth of oil peony.Moreover,after adding biochar to soil,soil pH,total nitrogen,total phosphorus,available nitrogen and available phosphorus in soil increased with the increasing of biochar addition.At the non-fertilization plots,6 kg/m~2 of biochar application had the greatest positive effects on plant height,root diameter and leaf SPAD of oil peonies.Compared with the plots no biochar applied,plant height and diameter increased by 10.43%and 10.69%,respectively.The contents of nitrogen and phosphorus in roots,stems and leaves of oil peonies were also highest at at the plots with 6 kg/m~2 of biochar applied.At the fertilization plots,4 kg/m~2 of biochar application had the greatest positive effects on plant height,root diameter and SPAD of oil peonies.The content of nitrogen in root sytems,stems and leaves of oil peonies increased by 12.26%,13.04%and 10.41%compared with the subplots of no biochar applied.Overall,plant height,root diameter,leaf SPAD value and nitrogen contents in different organs of oil peonies in the plots fertilized were greater than those of the plots not fertilized.Therefore,the amount of biochar applied to yellow soil for plantation of oil peony is best at a 4 kg/m~2 of applicated level.In summary,we found that the addition of biochar in yellow soil can effectively reduce the loss of nitrogen and phosphorus with the leaching solutions and surface runoff from fields planted by oil peony.Application of biochar to yellow soil can improve soil nutrients,which is conducive to the growth of oil peony.The addition of 4 kg/m~2 was the best.