Effects Of Organic Materials Replacing Nitrogen Fertilizer On Gas Emission,physicochemical Properties And Crop Yield In Fluvo-aquic Soil Under Wheat-maize Rotation

In view of the problems of nutrient loss,decrease of fertilizer utilization rate,soil compaction,fertility reduction and agricultural non-point source pollution caused by large amounts of nitrogen fertilizer input at present,the previous studies found that organic fertilizer replacing part of nitrogen fertilizer can improve soil fertility,improve fertilizer utilization rate,and reduce greenhouse gas emissions and soil ammonia volatilization.Therefore,based on the traditional nitrogen application rate in Huang-Huai-Hai Plain,the field experiment was carried out under the equal rate of N input.Six treatments were set as(1)Control(farmer’s practice of fertilizer rates,CF);(2)CF + straw(CFS);(3)nitrogen reduction 20% + straw(RFS);(4)20% cow manure +80%mineral nitrogen(M1F);(5)20% cow manure + 80% mineral nitrogen + straw(M1FS);(6)20%chicken manure + 80% mineral nitrogen(M2F).The effects of organic input on ammonia volatilization,greenhouse gas emission,soil properties and crop yield were measured and analyzed.The main results were as follows:(1)The cumulative ammonia volatilization of each fertilizer treatment was 1.74-3.62 kg·hm-2,and the ammonia volatilization flux and cumulative ammonia volatilization significantly decreased under straw returning,fertilizer reduction and organic fertilizer addition.Compared with CF,the ammonia volatile flux of CFS,RFS,M1 F and M2 F decreased by 0.75%-46.49%.Ammonia volatilization accumulation decreased by 2.55%-52.00%.Ammonia volatilization was closely related to soil ammonium nitrogen.The addition of straw and manure and nitrogen reduction of chemical fertilizer significantly weakened the correlation between soil NH4+-N concentration and ammonia volatilization.In addition,the NH4+-N content of soil under each fertilization treatment increased rapidly in the first 3 days and then decreased,and the NH4+-N content of soil under CFS treatment was the highest on the third day after fertilization.In addition,the addition of organic fertilizer significantly improved soil urease activity,M1 F,M2F treatment of soil urease activity increased by 18.75%-25.49% compared with CF treatment.(2)The N2 O emission flux showed a trend of first increasing and then decreasing.The N2 O emission flux was higher within one week after fertilization,and then maintained a relatively stable emission level.After rainfall or irrigation,the emission peak was weak.The cumulative emission of N2 O was CF>CFS>M1FS>RFS.Compared with CF treatment,M1 FS and RFS treatment can reduce N2 O emission by 18.21% and 42.38%,respectively.The cumulative CO2 emissions showed an increasing trend,and the order was M1FS>CFS>CF>RFS,in which the cumulative CO2 emissions of M1 FS treatment was 1.24 times that of CF.The cumulative CO2 emission of RFS treatment was reduced by 26.40% compared with CF treatment.Total N2 O emission is CF>CFS>M1FS>RFS,total CO2 emission is M1FS>CFS>CF>RFS,greenhouse gas emission intensity(GHGI)is CFS>CF>M1FS>RFS,global warming potential(GWP)is consistent with total CO2 emission.Overall,the addition of manure and straw increased GWP,and the organic replacement treatment of cow manure significantly reduced GHGI.(3)The additional organic fertilizer significantly reduced soil bulk density and improved soil porosity.Straw returning and partial replacement of fertilizer by organic fertilizer significantly increased the content of organic carbon in aggregates of all grain sizes and the content of large aggregates in soil.Compared with CF,the mass proportion of the water-stable large aggregates(diameter > 0.25 mm)increased,among which M1 F treatment had the best effect,with the highest mean weight diameter and geometric mean diameter,while the lowest fractal dimension.Increased application of organic fertilizer significantly increased the contents of total nitrogen,alkali-hydrolyzed nitrogen,nitrate nitrogen,ammonium nitrogen,soluble carbon,nitrogen and microbial carbon and nitrogen in 0-40 cm soil layer and increased soil enzyme activities.In wheat season,M2 F treatment had the best effect,while M1 F treatment had the best performance in maize season.In addition,CFS,M1 F and M2 F treatments significantly increased the normalized enzyme activity in 0-40 cm soil layer.In maize season,compared with CF treatment,M1 F treatment significantly increased soil EC/N value(C cycle related enzyme /N cycle related enzyme)and normalized enzyme activity,with the highest increase of 8.27% and 22.21%.(4)M1F and M2 F significantly increased the photosynthesis of wheat flag leaves and crop yield.In the wheat season,M1 F and M2 F treatments significantly increased the number of ear per mu and yield of wheat,and M2 F treatment increased by 15.53%.In the maize season,M1 F and M2 F treatments increased ear diameter,row number,100 grain weight and yield of maize,which increased by 11.53% and 15.40%,respectively,compared with CF treatment.In conclusion,the straw and cow manure input reduced soil bulk density,ammonia volatilization flux,ammonia volatilization accumulation and N2 O emission,weakened the correlation between soil NH4+-N concentration and ammonia volatilization,but increased CO2 emission,improved GWP and slightly reduced GHGI.Additionally,20% organic material substitution improved soil porosity,increased the aggregate organic carbon content of each particle size and the soil mass aggregate content,soil nutrient content,and soil enzyme activity.Meanwhile,they improved the intensity of crop photosynthesis and crop yield.Therefore,it was suggested as the optimum fertilization practice in northern Henan province.