Returning Organic Materials To The Field: Dynamic Impacts On Soil Carbon And Nitrogen Drip Irrigation

Crop straw and manure are important sources of fertilizer in the agricultural system.my country is rich in straw resources and the output of livestock manure is huge.However,the utilization rate of organic materials such as plants and livestock manure is low in China,and the effective return rate is less than 1/3.A large amount of organic materials cannot be used reasonably,which will inevitably bring about ecological damage and environmental pollution.For example,the burning of crop straw will increase air pollution,and the random disposal of untreated livestock and poultry manure will cause serious water pollution.Therefore,more and more attention has been paid to the research of returning organic materials such as plants and livestock manure to the fields.And applying organic materials as fertilizers into the soil is one of the effective ways of organic matter management and utilization.Tumuji Town,Zhalaite Banner,Xing’an League,Inner Mongolia Autonomous Region is located in a semi-arid area,with poor soil,thin soil layers,and lack of water,which severely restrict the yield of local crops.Drip irrigation technology under mulch has the effect of retaining water and moisture,and is widely promoted and applied locally.The long-term single drip irrigation technology under the mulch gradually makes the organic matter mineralized and decomposed after improving the soil.The addition of external organic matter can supplement carbon and nitrogen sources,activate soil carbon and nitrogen reservoirs,and promote the storage of carbon and nitrogen reservoirs in the soil.Therefore,this experiment selects three common organic materials in the test site,namely straw（MS）,pasture（FG）,and sheep manure（SM）,and conducts field fertilization experiments under drip irrigation under semi-arid mulch.Clarify the fertility effects of different organic materials on chestnut soil and the differences in the effects of soil nutrients during the growth period of maize,provide a theoretical basis for the semi-arid drip irrigation conditions under the condition of materials to return to the field to improve soil fertility,and select the most suitable local return to field Organic materials.The four treatments of maize straw（MS）,forage grass（FG）,sheep manure（SM）,and non-organic material control treatment（CK）are applied according to the carbon content of the local corn stalks returned to the field,and the nitrogen content is adjusted according to the equal carbon principle.Soil samples were collected during the maize growth period in 2019 to study the effects of different organic materials on the carbon and nitrogen pools of drip irrigation chestnut soil under semi-arid mulch.The results of the study are as follows:1.The return of organic materials to the field promotes the accumulation of soil organic carbon and total nitrogen during the corn growing period.Compared with the control,the return of organic materials to the field increased the content of soil organic carbon（SOC）,total nitrogen（TN）,soil organic carbon storage（SOCS）,and soil total nitrogen storage（TNS）.Among the three materials,the organic carbon（SOC）,total nitrogen（TN）,soil organic carbon storage（SOCS）,and total soil nitrogen storage（TNS）content under the SM treatment were significantly higher than other treatments,indicating SM treatment provides more carbon and nitrogen.2.The return of organic materials to the field promotes the accumulation of soil particulate organic matter and mineral combined organic matter during the corn growth period.Compared with the control photos,the return of organic materials to the field increased soil particulate organic carbon（POC）,soil particulate organic nitrogen（PON）,mineral-bound organic carbon（IOC）,and mineral-bound organic nitrogen（ION）.In addition,the soil particulate organic matter and its C/N are higher than the mineral-bound organic matter and its C/N,indicating that more active particulate organic matter is produced after the material is returned to the field and decomposed,and there is a significant or extremely significant negative correlation between each other,indicating The transformation relationship between particulate organic matter and mineral combined state.The distribution ratio of soil particulate organic carbon（POC）and soil particulate organic nitrogen（PON）is 36.78%-66.30%,8.95%-54.90%,which are relatively high,indicating that after the material decomposes,it is easier to generate particulate organic matter and easier to decompose And transformation.Among the three materials,the return of MS to the field is more conducive to the storage of particulate organic carbon;the return of SM to the field is more conducive to the storage of particulate organic nitrogen;the return of FG to the field is more conducive to the mineral-bound organic carbon The storage of MS is more conducive to the storage of mineral-bound organic nitrogen.3.Returning organic materials to the field will increase soil soluble organic matter content and soil carbon pool and nitrogen pool index during the corn growing period.Compared with the control photos,the return of organic materials to the field during the corn growth period increases the proportion of soil soluble organic carbon（DOC）and soil soluble organic nitrogen（DON）in soil organic carbon and total nitrogen,among which MS and FG is the best treatment,which indicates that plant-based organic materials are returned to the field to produce more soluble organic matter.Among the three materials,MS treatment can increase the content of soluble organic matter（DOC,DON）,easily oxidizable organic carbon（EOC）,soil carbon pool index（CPMI）and nitrate nitrogen（NO₃^--N）in the soil.Soil Nitrogen Pool Index（NPMI）,different materials have different effectiveness,but in general,returning organic materials to the field is better than returning to the field without organic materials.The content of ammonium nitrogen（NH₄⁺-N）under CK treatment is higher than that with material treatment,indicating that the absorption of ammonium nitrogen（NH₄⁺-N）by crops,the conversion of ammonium nitrogen（NH₄⁺-N）and the loss of nitrogen are the cause of ammonium The reason for the decrease of nitrogen（NH₄⁺-N）content.4.The return of organic waste to the field will increase the soil microbial carbon and microbial nitrogen content during the corn growth period.Compared with the control photos,the organic wastes returned to the field during the corn growth period can effectively increase the soil microbial biomass carbon and nitrogen（MBC,MBN）content,reduce the microbial biomass C/N,increase the qMBC and qMBN values,and increase the The activity of soil organic matter and the utilization of nitrogen.The soil metabolic entropy（q CO₂）content of organic waste treatment during the period of vigorous growth and development is significantly lower than that of CK treatment,indicating that the addition of organic waste can promote the utilization of carbon by microorganisms and reduce respiratory consumption.Among the organic waste,returning MS to the field significantly increases the content of microbial biomass carbon（MBC）and microbial biomass nitrogen（MBN）in the soil,and also significantly increases the proportion of microbial biomass organic matter in soil organic carbon and total nitrogen.Indicating that returning straw to the field is more conducive to the storage of microbial biomass.In general,returning organic materials to the field under drip irrigation under semi-arid mulch is conducive to the storage of carbon and nitrogen content in the soil,promotes the storage of nutrients in the thinly cultivated chestnut soil,activates soil active organic matter,and promotes the accumulation and renewal of active organic matter.Among them,the application of SM can promote the storage of soil organic carbon and total nitrogen,and the application of MS is more conducive to the accumulation of soil active organic matter.