| Biogas slurry is a brown liquid formed by anaerobic fermentation of organic waste,rich in nitrogen,phosphorus,potassium and other nutrients,and contains a variety of amino acids,auxins and active enzymes and other nutrients.Therefore,it has the strong quick-effect nutrition ability and the high nutrient utilization rate.From the perspective of resource priority,recycling economy and environmental friendliness,biogas slurry returning to the field is the most ideal treatment.The application of biogas slurry can not only meet the nutrient requirements of crops,but also improve soil fertility and promote improvement of soil quality.In this study,field experiments were performed,biogas slurry was used to replace chemical fertilizer to plant potatoes.A total of 10 biogas slurry application plots were set up,with clear water and conventional chemical fertilizers as controls.The effects of different amounts of biogas slurry to the field on potato growth and development,yield,nutrient quality,and soil environmental quality were discussed,which provide theoretical basis and practical application for the safe agricultural production of biogas slurry on alluvial paddy soil in the Chengdu Plain area.The main findings are as follows:(1)Compared with clean water control and conventional chemical fertilizer treatment,proper biogas slurry treatment can promote potato yield,improve nutritional quality,and to a certain extent,increase potato mineral element content and reduce the risk of heavy metal contamination.When the biogas slurry application amount was controlled within the range of 76000-94000 kg/hm~2(BS5-BS7 plots),the physical quality and yield of potatoes were at a high level;when the application amount was controlled at 85000-94000 kg/hm~2(BS6-BS7 plots),the content of crude protein,dry matter,vitamin C,starch,and reducing sugar in potatoes was high,and the nutrition was rich;when the application amount was controlled in the range of 85000-112000 kg/hm~2(BS6-BS8 plots),the content of mineral elements in potatoes reached a relatively high level;when the application amount was controlled within the range of 40000-112000 kg/hm~2(BS1-BS8 plots),the contents of heavy metals in potatoes were all at a low level,and did not exceed the Corresponding standard limits in GB 2762-2017 food pollutant limits.Combined with potato yield,nutritional quality,mineral elements and heavy metal content,when the application amount of biogas slurry was controlled within the range of 85000-112000 kg/hm~2(BS6-BS8 plots),the potato yield was the highest,the nutritional quality was better and safer,and the application of biogas slurry economic benefit was better.(2)Biogas slurry is not only rich in nitrogen,phosphorus,and potassium nutrients,but also rich in organic matter,amino acids,humic acid,growth hormone and other nutrients,as well as a variety of trace elements,the application of proper amount of biogas slurry is conducive to improve the physical and chemical properties of soil and the content of soil mineral elements.The p H value of the soil in the biogas slurry treatment area was higher than that in the clear water control and conventional chemical fertilizer plots,which has a significant effect on preventing and controlling soil acidification.When the biogas slurry application amount was controlled within the range of 112000-130000 kg/hm~2(BS8-BS9 plots),the content of organic matter and cation exchange in soil was high;when the application amount was controlled within the range of 850000-112000 kg/hm~2(BS6-BS8 plots),the contents of total nitrogen,total phosphorus,total potassium,alkali-hydrolyzed nitrogen,available phosphorus and available potassium in soil were at a high level;when the amount was controlled within the range of 76000-940000 kg/hm~2(BS5-BS7 plots),the content of soil mineral elements was at a high level;In the range of40000-940000 kg/hm~2(BS1-BS7 plots),the heavy metal content in the soil was at a low level,Moreover,it satisfied the limit value of soil pollution risk screening value of GB15618-2018 agricultural land.Therefore,the study believed that when the application amount of biogas slurry was controlled in the range of 85000-94000 kg/hm~2(BS6-BS7plots),the soil fertility was higher,the soil environmental quality and the application of biogas slurry environmental benefits were better.(3)The application of biogas slurry is also associated with the risk of contamination of plants and soil heavy metals.When the biogas slurry application amount was controlled within the range of 58000-94000 kg/hm~2(BS3-BS7 plots),the enrichment factor of potato heavy metals was at a low level;when the amount was controlled between 40000-76000kg/hm~2(BS1-BS5 plots),the soil heavy metal pollution was at a low level.From the comprehensive quality index of potato-soil system,all biogas slurry treatment plots were cleaner,and the overall quality of potato-soil system was relatively higher.Combined with the Nemerow pollution index,potential ecological risk index,enrichment coefficient and correlation coefficients,Cd was more likely to accumulate in the soil,more harmful to the soil,and more easily absorbed by potatoes.So.it is necessary to prevent and control Cd in practical agricultural production of biogas slurry.In summary,in the alluvial paddy soil in Chengdu plain,controlling the application amount of biogas slurry within a certain range,and applying biogas slurry reasonably to plant potatoes can promote its yield and quality,and also improve soil fertility and ensure soil environmental quality.From the comprehensive consideration of factors such as the effect of biogas slurry on potato growth and development,yield,quality,and soil quality,the best application amount of biogas slurry is 85000-94000 kg/hm~2(BS6-BS7 plots).at this time,biogas slurry agricultural economic benefits and environmental benefits can achieve the best balance. |
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