Effects Of Biogas Slurry And Biochar Application On Soil Physicochemical Properties And Lotus Root Growth

Lotus root is the aquatic vegetable with the largest planting area in our country.It is rich in nutrition and can produce good economic benefits.However,during the planting process,there are problems of soil acidification,nutrient imbalance and fertility decline caused by excessive fertilizer application,which reduces the yield and quality of lotus root.Therefore,how to improve soil fertilizer efficiency while reducing the amount of chemical fertilizers is the current dilemma in the development of the lotus root industry.Based on the current large amount of farming waste and the difficulty of harmless and resourceful utilization,biogas engineering is currently the most common and effective comprehensive utilization method for dealing with farming waste,especially livestock and poultry waste.The products of biogas projects contain rich nutrients such as nitrogen,phosphorus,and potassium,which can be absorbed and utilized by crops.In addition,planting and breeding waste can generate biochar after high-temperature pyrolysis and carbonization under oxygen-isolated conditions.Biochars,with large surface area,rich pore structure and functional groups,can improve soil physicochemical properties and enhance soil fertility.Application of biogas slurry and biochar are effective way to reduce the addition of chemical fertilizer and improve soil quality and efficiency.In this study,the effects of single and combined application of biogas slurry and biochar on soil physicochemical characteristics and enzymatic properties were explored through pot experiments.The effects of biogas slurry and biochar on the botanical traits,yield and quality of lotus root plants were studied.This study will provide a theoretical basis for the scientific application of biogas slurry and biochar and the sustainable development of lotus root industry.The main findings are as follows:(1)Application of biogas slurry can increase soil nutrient content and enzyme activity,and the degree of improvement increased with the increase in biogas slurry application quantity.Among these treatments,100% replacement of nitrogen by biogas slurry(A2B0)had the best effect on increasing soil nutrient content.Compared with the control treatment and single addition of fertilizer treatment,the soil total nitrogen,soil total phosphorus and soil available potassium content under the action of A2B0 increased by 22%,83%,392% and 18%,32%,125%,respectively,and the soil enzyme activity was the highest.The application of rice straw biochar and swine manure biochar could increase soil p H and soil nutrient content.When the biochar application rate was2%,except for soil alkaline nitrogen,swine manure biochar had a better effect on nutrient content than rice straw biochar.Moreover,the soil enzymatic properties were significantly improved under the action of rice straw biochar and swine manure biochar.The combined application of biogas slurry and swine manure biochar increased the soil total nitrogen,total phosphorus,available phosphorus,available potassium and organic carbon content was better than that of biogas slurry and swine manure biochar alone,and the combined application of 100% replacement of nitrogen by biogas slurry with2%-350°C swine manure biochar(A2B2)had the best effect on soil enzyme activity.(2)Addition of biogas slurry can improve the botanical characters of lotus root plants,and A2B0 treatment can promote the growth of lotus root leaves,floating leaves and petioles.The leaves dry weight,stem dry weight and chlorophyll content of vertical leaves had also been significantly improved.Compared with the control treatment,the increase rate was 166%,270%,and 38%.Application of rice straw biochar and swine manure biochar can also promote the growth of lotus root plants,and the growth of floating leaves,vertical leaves,petioles and plant biomass had been significantly improved,as well as the chlorophyll content of vertical leaves.2%-350°C swine manure biochar(A0B2)had the best improvement effects.Under the action of the combined application of biogas slurry and swine manure biochar,the improvement effect on the botanical traits of lotus root plants was better.Under the action of A2B2 treatment,the promotion effect on lotus root plant growth,biomass and vertical leaf chlorophyll was the best.(3)The yield and quality of lotus root were improved after the application of biogas slurry,and A2B0 treatment had the best effect on the increase of lotus root yield,starch,crude fiber,polysaccharide and mineral element content.In addition,compared with the treatment of single application of chemical fertilizer,the nitrate content of lotus root was significantly reduced by 11% under the A2B0 treatment.After applying rice straw biochar and swine manure biochar,the yield and quality of lotus root were improved.Among these treatments,A0B2 treatment had the greatest improvement in lotus root yield,starch content,crude fiber,polysaccharide,and magnesium content.Compared with the control group,the nitrate content of lotus roots significantly increased under the action of single chemical fertilizer treatment and biochar treatment.Compared with the single chemical fertilizer treatment,the nitrate content of lotus roots decreased when applying rice straw biochar,500℃ swine manure biochar,and 650℃swine manure biochar at 2% application rate.After application of biogas slurry combined with swine manure biochar,except for nitrate,the yield and quality of lotus root were significantly improved compared with the single addition of biogas slurry and biochar.The yield and quality of lotus root reached the maximum under the action of A2B2 treatment.After the application of biogas slurry and biochar,the heavy metal content of lotus root was lower than the limit value in the lotus root industry standard,and the short-term application of each treatment would not cause the risk of excessive heavy metals in lotus root.