Effect Of Biochar Addition On Soil Organic Chemical Composition In Ningxia Irrigation Area

The effects of biochar on soil organic matter have been extensively studied,but how biochar affects the chemical composition of native soil organic matter is not clear,especially in farmland ecosystems.Based on the five-year localization experiment of paddy soil in Ningxia irrigation area,on the one hand,the chemical constituents of organic matter in soil were extracted by solvent extraction and CuO oxidation.On the other hand,the basic physical and chemical properties of soil and the morphological indexes of rice roots were determined by routine detection and root scanning.The performance of rhizosphere effect is obtained by principal component analysis.The key questions of biochar addition to the composition and stability of soil organic matter in rice fields were answered.The effects of biochar addition on paddy soil were further explained by physical and chemical indicators and rice growth.Four biochar levels were designed in the research,which were C0 treatment?0 t/ha biochar?,C1treatment?4.5 t/ha biochar?,C2 treatment?9 t/ha biochar?and C3 treatment?13.5 t/ha biochar?respectively.The test was carried out on the basis of conventional fertilization?300 kg/ha N,90 kg/ha P₂O₅,90 kg/ha K₂O?,and each treatment was repeated for three times.The main conclusions are as follows:?1?The short-chain alcohols and short-chain acids mainly derived from microorganisms and long-chain compounds and sterols mainly derived from plants that were obtained by solvent extraction of soil organic matter in paddy fields in Ningxia.The chemical composition obtained by CuO oxidation were mainly lignin-derived phenols,such as vanillyl,syringyl,cinnamyl-based acids,alcohols and aldehydes,and other benzene-rings.?2?The addition of biochar can increase the degradation of soil organic matter components,but reduce the degree of oxidation of the compounds.Compared with C0 treatment,the research has shown that C1 treatment can significantly reduce plant-derived lignin by 31.19%,long-chain composition content by 32.7%,ergosterol content by 25.9%,but significantly increase short-chain microbial-derived compounds by 42.9%;C2 treatment decreased short-chain compound by 20.1%,15.4%long-chain compound,8.9%ergosterol content,and lignin content increased by 4.59%;biochar addition in C3treatment still reduced various organic compositions content.However,the addition of biochar significantly reduced the degree of oxidation of the aldehyde groups within the lignin.?3?The addition of biochar did not significantly increase the available nutrients content and pH in the paddy soil in Ningxia,and even reduced the content of available nitrogen by 7.48%and 5.04%available potassium in low level of biochar treatment,But significantly increased the organic carbon content in the soil.The study showed that compared with C0 treatment,C1,C2,and C3 treatments significantly increased soil TOC by 24.26%,50.59%,and 36.69%,respectively.?4?The addition of biochar had different effects on the growth of rice roots.The main effect was that the addition of biochar can promote the growth of roots during tillering stage.The low level of biochar treatment in jointing stage can promote the growth of roots,while the effect of high level of biochar treatment on growth of roots was inhibition,the promotion of low level of biochar treatment in the filling stage reduced,while high carbon can delay root senescence.?5?Principal component analysis showed that the rhizosphere effect at the tillering stage had a clear distinction among the active nutrient content factors,while the organic matter chemical composition and degradation parameters were significantly different among treatments.In the C0treatment,the two main components of the free compound content and the lignin degradation parameter were clearly distinguished between the rhizosphere and the non-rhizosphere,and the carbon treatment had a clear distinction in the lignin content.