| Biogas slurry is a kind of high quality organic liquid fertilizer,which is rich in nutrients necessary for plant growth.Biogas slurry combined with chemical fertilizer can reduce the amount of chemical fertilizer,improve soil fertility and reduce agricultural production investment,which is beneficial to the sustainable development of agriculture.In this study,cow dung anaerobic digestion biogas slurry was used as the research object,and silage maize’ Dongrun 58’ was used as the indicator crop.The field plot experiment was used to study the optimal consumption of biogas slurry directly returning to field and the effect of biogas slurry compound returning to field on maize growth,yield and soil quality,so as to provide scientific guidance and theoretical basis for the efficient utilization of biogas slurry.The main conclusions are as follows:1.The biogas slurry irrigation at 450 m3/hm2 significantly promoted the improvement of soil quality.Compared with conventional fertilization,R0.25 of biogas slurry irrigation at 450 m3/hm2 significantly increased by 5.4%,and soil bulk density significantly decreased by 13.0%.Soil organic matter,total nitrogen,total phosphorus,available nitrogen,available phosphorus and available potassium increased by 53.4%,78.6%,75.7%,164.9%,87.2%and 46.2%,respectively.Under the treatment of biogas slurry irrigation at 450 m3/hm2,soil microbial quantity and enzyme activity increased significantly,and soil microbial biomass carbon,nitrogen and phosphorus content increased by 44.2%,149.0%and 182.6%,respectively.At the same time,biogas slurry irrigation at 450 m3/hm2 significantly increased soil microbial entropy and decreased soil microbial biomass carbon-nitrogen ratio.2.The growth index,root index,photosynthesis and yield of maize under biogas slurry irrigation of 450 m3/hm2.Compared with conventional fertilization,the plant height of maize under biogas slurry irrigation of 450 m3/hm2 significantly increased by 24.9%,and the total root length,total root surface area,total root volume and branch number significantly increased by 44.9%,57.9%,73.3%and 47.2%,respectively.Intercellular CO2 concentration decreased by 15.9%,net photosynthetic rate and water use efficiency increased by 12.4%and 21.3%,respectively.Biogas slurry irrigation at 450 m3/hm2 significantly increased maize yield by 33.5%and dry matter by 10.3%.According to the numerical simulation of yield and biogas slurry application rate,the maximum biogas slurry application rate was 480 m3/hm2.3.Compared with conventional fertilization,R0.25 of 45%biogas slurry+55%chemical fertilizer treatment significantly increased by 17.6%,and soil bulk density significantly decreased by 16.5%;The contents of soil organic matter,total nitrogen,total phosphorus,available nitrogen,available phosphorus and available potassium in 45%biogas slurry+55%chemical fertilizer treatment increased by 71.5%,40.5%,24.2%,65.6%,96.9%and 162.6%,respectively.The total number of soil bacteria increased first and then decreased with the proportion of biogas slurry.The total number of bacteria,bacteria and actinomycetes in 45%biogas slurry+55%chemical fertilizer treatment increased by 173.4%,160.3%and 312.5%,respectively,and the number of fungi decreased by 66.0%.The activities of urease,phosphatase and invertase were significantly increased by 41.3%,29.0%and 147.5%,respectively.The contents of soil microbial biomass carbon,nitrogen and phosphorus were significantly increased by 70.0%,195.6%and 91.6%,respectively,compared with conventional fertilization.The soil microbial entropy was significantly increased by 61.7%.4.The compound fertilizer of biogas slurry had significant effect on maize growth and yield,and the treatment of 45%biogas slurry+55%chemical fertilizer was the best.Compared with conventional fertilization,the plant height and stem diameter of maize treated with 45%biogas slurry+55%chemical fertilizer increased by 23.8%and 22.8%,respectively.The total root length,total root surface area,total root volume,branch number and cross number of maize significantly increased by 34.1%,32.6%,66.2%,44.3%and 27.9%,respectively.stomatal conductance and chlorophyll content increased by 28.6%and 16.3%,and intercellular CO2 concentration decreased by 28.5%.The maize yield and dry matter weight of 45%biogas slurry+55%chemical fertilizer treatment were significantly increased by 40.9%and 16.2%compared with those of conventional fertilization,respectively.Considering the response indexes of silage maize growth,yield and soil quality,the optimal consumption of direct returning biogas slurry from cow dung anaerobic digestion was 450m3/hm2～480 m3/hm2,and the optimal proportion of compound returning biogas slurry was 45%biogas slurry+55%chemical fertilizer. |
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