Partially Replacement Of Mineral Fertilisers With Poultry Biogas Slurry As Nutrient Solution For Soilless Culture

In recent years,with the rapid development of animal husbandry,a large number of animal excreta have been posing a potential threat to the environment,and anaerobic digestion has become an important way to utilize wastes in a resourceful manner.This has also produced a large amount of biogas slurry.Poultry biogas slurry is rich in nutrients needed by plants and is an important part of biogas slurry.However,there are relatively few researches on poultry biogas slurry.The configuration of the nutrient solution requires a large amount of mineral fertiliser,which becomes a way for poultry biogas slurry to enter the crop nutrient cycle.In order to make effective use of poultry biogas slurry and promote sustainable development of agriculture,this study first analysed the composition of poultry biogas slurry,then used lettuce,biogas slurry and mineral fertilisers as raw materials to conduct lettuce hydroponics experiments to evaluate poultry biogas slurry in lettuce.The feasibility of replacing mineral fertilisers in hydroponics production and its effects on lettuce growth,quality,heavy metal content,and economy and ecology;followed by the application test of poultry biogas slurry nutrient solution in substrate culture.The main findings are as follows:1.The analysis of physicochemical properties and stability of poultry biogas slurry shows that poultry biogas slurry contains abundant N(4001.30 mg·L-1)and K(3625.00 mg·L-1)elements,but it is also associated with Hoagland nutrient solution.Compared with the proportion of nutrients,the contents of P,Ca and Mg are relatively small;the content of heavy metals in biogas slurry is lower than the national fertiliser standard;the physicochemical properties of biogas slurry are stable in the short term.It shows that poultry biogas slurry can be used as a liquid fertiliser.2.The experiment of poultry biogas slurry instead of fertiliser hydroponic lettuce test showed that compared with the control(half-strength Hoagland nutrient solution),the poultry biogas slurry can partially replace the mineral fertiliser(in this study,it replaces 50%).The addition of poultry biogas slurry will not cause adverse effects on lettuce growth,even promote root growth,significantly increase soluble sugar content,and significantly reduce nitrate content.Although,compared with the control,the content of heavy metals increased after application of biogas slurry,but it was still in the safe range.In addition,the application of poultry biogas slurry can reduce the production cost of lettuce hydroponics by 25%,reduce energy consumption by 42%,and reduce greenhouse gas emissions by 41%.Therefore,the poultry biogas slurry can be used as a partial replacement of mineral fertilisers in lettuce hydroponics,and the key is to control the electrical conductivity and supplement the nutrients lacking in the biogas slurry.3.The application of poultry-biogas-slurry nutrient solution in vegetable substrate culture was studied.The results showed that poultry-biogas-slurry nutrient solution(1.3%biogas slurry+quarter-strength Hoagland nutrient solution)did not adversely affect the growth and quality of the substrate culture lettuce,oiled wheat dish,garland chrysanthemum,non-heading Chinese cabbage,spinach and tomato.However,the yield of cucumber has decreased.Therefore,poultry biogas slurry can partially replace mineral fertilisers as a nutrient solution for lettuces,oiled wheat vegetables,garland chrysanthemums,non-heading Chinese cabbage,spinach,cucumbers and tomato,and can meet the nutrient requirements of leafy vegetables and tomato crops.