| In this study,aiming at the problems of large amount of farmed manure,low utilization of resources and increasingly serious environmental pollution,alfalfa was taken as the research object.First,the effects of different nitrogen rates and additives on soil ammonia volatilization and nitrogen and phosphorus nutrient content were investigated through indoor culture experiments.Then,the effects of adding humic acid to farmed manure on alfalfa yield,growth and development,soil ammonia volatilization,nitrogen leaching and nitrogen and phosphorus balance were studied through soil column leaching experiments.The conclusions of this paper are as follows:（1）The increase of nitrogen application rate in cattle farm slurry will increase the ammonia volatilization rate and ammonia volatilization accumulation in soil.When the application rate is90·kg·N·hm-2,it will have the least effect on ammonia volatilization rate and reduce the ammonia volatilization accumulation loss.The amount of slurry applied in cattle farm affects the loss of nitrogen and phosphorus in soil.With the increase of slurry applied in cattle farm,the ammonium nitrogen content and available phosphorus content decreased by 3.41～21.01 times and 1.28～6.04 times,but the nitrate nitrogen content in soil increased by 1.81～3.06 times.（2）Adding different additives to cattle farm slurry can reduce ammonia volatilization loss,and the total nitrogen content of BSHA treatment with humic acid was significantly higher than that of other treatments on the 14th day of culture.Adding different substances in cattle manure slurry will change soil nutrient content,and the content of ammonium nitrogen and nitrate nitrogen in soil treated with humic acid will decrease.After adding humic acid and biochar,the content of available phosphorus finally stabilized at about 16.19 mg·kg-1.Adding humic acid to cattle manure will reduce soil urease activity compared with urea.（3）Adding humic acid to the cattle farm slurry can significantly increase the yield of alfalfa.The yield of fertilizer treatment with humic acid was significantly higher than that without application,and the average yield of three crops reached 44.46%.The plant height,stem diameter and leaf width of humic acid treatment increased by 1.64%～10.82%,3.14%～16.96%and 0.09%～2.66%respectively.The nitrogen uptake and nitrogen use efficiency of fertilizer treatment with humic acid were also significantly higher than those without humic acid,increasing by 14.05%～28.64%and 12.32%～82.39%respectively.The absorption of phosphorus increased by 0.69%～57.61%,and the apparent utilization rate of phosphorus increased by 66.42%when BSHA treatment was added to cattle farm slurry.（4）The ammonia volatilization rate and accumulation of humic acid treatment were significantly lower than those of other treatments,with FBS treatment combined with chemical fertilizer and manure decreased by 23.36%,BSHA treatment combined with humic acid in cattle farm slurry decreased by 64.49%and FBSHA treatment combined with chemical fertilizer and manure decreased by 71.27%.On the whole,the change of nitrate leaching concentration is consistent with total nitrogen,and the cumulative leaching loss of nitrate nitrogen accounts for 46.38%～52.57%of total nitrogen.Comprehensive analysis of alfalfa yield,nitrogen and phosphorus absorption and utilization rate,nitrogen and phosphorus balance by adding humic acid into cattle farm slurry can significantly reduce soil nitrogen and phosphorus surplus,improve nitrogen and phosphorus utilization rate and reduce the risk of agricultural non-point source pollution.When the nitrogen intake of manure is 90 kg·hm-2,the nitrogen and phosphorus surplus by adding humic acid will be significantly reduced. |
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