Effects Of Combined Organic And Inorganic Fertilizers Use On Salinized Soil Greenhouse Gas Emissions And Sorghum Growth In Hetao Irrigation Distrcit

Hetao Irrigation District is an important grain producing area in Inner Mongolia and one of the areas most widely affected by soil salinization.Fertilization is the main way to improve the salinized soil fertility and promote crop growth in irrigation areas.However,the increasing amount of nitrogen fertilizer and traditional fertilization methods may lead to nutrient imbalance,reduction of nitrogen fertilizer utilization rate,and large emissions of greenhouse gases while improving crop yield.This study conducted a two-year field plot experiment from 2021 to 2022,following the principle of equal nitrogen replacement,to conduct a combined application experiment of nitrogen and organic fertilizers.The experiment was conducted with no nitrogen fertilizer treatment（CK）,optimizing the nitrogen fertilizer application rate of 180 kg/hm² single fertilizer（N1T0）,40%organic fertilizer replacement fertilizer（N1T1）,60%organic fertilizer replacement fertilizer（N1T2）,conventional nitrogen fertilizer application rate of 240 kg/hm² single fertilizer（N2T0）,and40%organic fertilizer replacement fertilizer（N2T1）There are a total of 7 treatments where60%organic fertilizer replaces chemical fertilizer（N2T2）.Exploring the effects and interrelationships of organic and inorganic fertilizer application ratios on soil physical and chemical properties,sorghum growth characteristics,and greenhouse gas emissions from farmland under different nitrogen application levels,providing theoretical basis and practical guidance for saline soil improvement in irrigation areas,efficient utilization of nitrogen fertilizer resources,and carbon sequestration and emission reduction in farmland.The main conclusions are as follows:（1）Increasing the amount of nitrogen and Manure decreased soil bulk density by0.64%～10.32%,increased soil porosity by 0.91%～18.81%,and increased soil moisture content by 0.19%～24.70%;The combined application of organic and inorganic fertilizers reduced soil p H by 0.03%to 6.77%and total salt by 0.86%to 77.46%.Increasing the level of nitrogen application and Manure will increase the content of soil nitrate nitrogen and ammonium nitrogen;The combination of organic and inorganic fertilizers can increase the content of total nitrogen,organic matter,and alkaline nitrogen in the soil.（2）The flux of N₂O and CO₂ emissions increases with the increase of nitrogen application level,while the cumulative emissions decrease with the increase of organic substitution ratio;The cumulative absorption of CH₄ decreases with the increase of nitrogen application level.Greenhouse gas emission intensity showed an increasing trend with the increase of nitrogen application rate and organic substitution proportion.The two-year warming potential（GWP）and emission intensity（GHGI）showed that 40%Manure was the best alternative to chemical fertilizer.（3）Increasing nitrogen application level can increase the plant height,stem diameter and leaf chlorophyll content of wine making sorghum,and the treatment of 40%Manure replacing chemical fertilizer is the best.The dry matter quality of sorghum increased with the increase of nitrogen application level.At maturity,the dry matter quality of 40%Manure instead of chemical fertilizer treatment was the highest,which increased by 0.71%～18.87%compared with other treatments.（4）The nitrogen uptake,nitrogen utilization efficiency and partial productivity of nitrogen fertilizer under 180 kg/hm² nitrogen application rate were higher than 240 kg/hm²,and 40%Manure instead of chemical fertilizer was the best.The combination of nitrogen fertilizer and organic inorganic fertilizer can improve the yield of brewing sorghum,with the40%organic substitution treatment having the highest grain yield,which is 6.63%～24.14%higher than other treatments under the same nitrogen application rate.Considering the changes of yield,growth status,nitrogen utilization rate and soil greenhouse gas emissions of brewing sorghum,Manure instead of 40%chemical fertilizer at the nitrogen application rate of 180kg/hm² is the more appropriate nitrogen fertilizer amount and organic ratio for brewing sorghum planting in Hetao irrigation area.