Response Of Soil Physical And Chemical Properties To Biochar Application In Degraded Farmland

Soil erosion is one of the main causes of farmland soil degradation,which causes the continuous loss of nutrient-rich topsoil and reduces the effect of soil water retention and fertilizer retention.As a soil improver,biochar has been widely applied to tillage soil.Biochar application can not only reduce greenhouse gas emissions,but also improve soil physical and chemical properties.However,there are few studies on the effects of biochar on soil improvement in degraded farmland.In this paper,the effects of 0%,4% and 8% biochar on soil moisture content,available P,alkali-hydrolyzable N,organic matter and alfalfa yield were studied by simulating 3 erosion degrees of farmland brown soil in Shenyang area,so as to provide certain theoretical basis and technical support for the application of biochar in eroded degraded farmland.The main results are as follows:(1)The degree of erosion and biochar application had no significant influence on soil water content,and soil depth was significantly positively correlated with soil water content.Among the three treatments,the lowest moisture content in the unplanted alfalfa plot and the unplanted alfalfa plot appeared in moderate erosion and uneroded plot respectively,and the overall change of moisture content in the year was the highest in the strongly eroded plot.(2)Both the erosion and biochar application had significant effects on soil available P.The available P content at the three biochar applied levels in the soil with different degrees of erosion had the following changes: uneroded> moderate erosion> strong erosion(P <0.05).In the 0-20 cm soil layer,the available P content was 24.74% and 28.91% higher than that of moderate erosion,and 130.58% and 64.48% higher than that of intense erosion.As a whole,the content of available P in soil was as follows: 8% biochar>4%biochar>0%biochar(P<0.05).The available P of 4% biochar ranges from 54.77% to 211.57%,while that of 8% biochar ranges from 106.00% to 352.01%.Under the conditions of non-erosion and moderate erosion,the available P content in alfalfa planted plots was significantly increased compared with that in unplanted plots,but decreased under intense erosion.(3)Both the degree of erosion and the application of biochar had no regular effect on soil alkalytic N.However,the comparison of alkali-hydrolyzed n content between alfalfa planting plots and non-planting plots showed that the alkali-hydrolyzed N content in alfalfa planting plots was higher than that in non-planting plots with the same degree of erosion and the application of biochar,and the difference between the two plots was slightly reduced after the application of biochar.(4)Biochar application was found to have a significant effect on soil organic matter uptake(P<0.05).After biochar was applied,the content of soil organic matter increased with the increase of biochar content,showing as follows: 8% biochar >4% biochar >0% biochar.The organic matter of 4% biochar increased from 24.16% to 31.41% compared with 0% biochar,and the organic matter of 8% biochar increased from 56.61% to 68.34% compared with 0% biochar,while planting alfalfa had no significant effect on soil organic matter content.This indicates that biochar has a significant effect on soil organic matter,and the higher the biochar is applied,the better the effect will be.However,according to the correlation analysis,soil erosion had no significant effect on organic matter content(P>0.05).(5)Biochar was found to increase alfalfa yields.Under the condition of no erosion,the alfalfa yield in the plots with 4% biochar and 8% biochar was significantly higher than that in the plots without biochar,while the yield in the plots with 4% biochar was higher than that without biochar,which was 52.10% and 32.77% higher than that without biochar.That is,with the increase of biochar content,the yield of alfalfa began to decline,and the inhibition of biochar on alfalfa growth began to appear.After soil erosion occurred in farmland,the yield of alfalfa increased with the increase of biochar content.Especially under strong erosion,the yield of alfalfa increased by 197.22% when 8% biochar was applied compared with that of the plots without biochar.It can be seen that the application of biochar can effectively alleviate the reduction effect caused by erosion degradation.