| Excessive or single use of chemical fertilizers in agricultural production will cause soil hardening and environmental pollution.The bio-organic fertilizer prepared with agricultural waste can not only improve soil structure,increase soil fertility and improve crop quality,but also achieve the purpose of resource utilization of agricultural waste.Rich in porous structure and having a large number of plant fibers,pomelo peel has the potential to be made into adsorbents or carriers of slow-release fertilizers because it can absorb bacteria and nutrients and provide passages for the release of bacteria and nutrients.However,the unfixed shape and unstable chemistry limit its potential.In order to improve its performance,it is necessary to change its physical property and chemistry.This paper studied the preparation and effect of Liang ping pomelo peel-based compound microbial slow-release fertilizer.The performance of nitrogen fixing bacteria and phosphorus and potassium solubilizing bacteria used in microbial fertilizers were identified and the production conditions were optimized.Taking Bacillus megaterium as phosphorus solubilizing bacteria,its phosphorus solubilizing capacity is 209.04±4.22 mg/L,and the optimum culture conditions are 1.5%molasses,1.45%soybean powder,1%magnesium sulfate,28℃and 180 r/min;Bacillus gelatinosus as a potassium dissolving bacterium,its potassium dissolving ability is 15.57±0.12 mg/L,and the optimum culture conditions are 1.5%molasses,1.45%peptone,1%magnesium sulfate,28℃and 180 r/min;As a nitrogen fixing bacterium,Paenibacillus polyxa has a nitrogen fixing ability of 340.42±22.4 mg/L.the optimum culture conditions are 1.5%molasses,1.45%defatted soybean powder,1%magnesium sulfate,28℃and 180 r/min.Pomelo peel powder was modified by carbonization,isopropanol,phosphoric acid,ferric chloride and hydrogen peroxide.The study analyzed surface functional groups,element content,morphology and specific surface area of modified and unmodified pomelo peel powder,as well as analyzed the adsorption capacity of nitrate nitrogen,phosphate and potassium ions in different p H environment,different adsorption system concentration and different time to explore its adsorption mechanism.The results show that the content of iron in pomelo peel powder modified by ferric chloride increase significantly,the surface functional groups are more abundant,and the surface become coarser and more dense pores because of being covered by iron compounds;The adsorption effect of nitrate nitrogen and phosphate is better in acidic environment,and the adsorption effect of potassium ion is better in alkaline environment;The adsorption mode of nitrate nitrogen is mainly monolayer physical adsorption,with the maximum adsorption capacity of 36.95±3.52 mg/g;the adsorption mode of phosphate and potassium ions is mainly chemical adsorption,with the maximum adsorption capacity of46.76±0.12 mg/g and 15.4±2.2 mg/g respectively;The fixed amount of functional bacteria was 3.67±0.15×10~8pieces/g.The modified pomelo peel-based compound microbial slow-release fertilizer is composed of inner core,inner membrane,pomelo peel powder layer and outer membrane.With core-shell structure,its surface outer membrane layer is intact,smooth and without cracks,and there are micro-pores on the surface to facilitate the release of nutrients.The effective viable number of the finished fertilizer is 0.35±0.01×10~8pieces/g,total nitrogen content of 4.52±0.12%,total phosphorus content of 1.75±0.32%,total potassium content of 12.87±0.65%,organic matter content of 52.14±0.42%,water content of 16.97±2.46%and p H of 6.07±0.01.The heavy metal elements did not exceed the standard,which met the standard of biological organic fertilizer NY884-2012.Nutrient release:total nitrogen released 31.41%on the first day,95.6%on the 11th day and 99.01%on the 28th day;Total phosphorus was released 45.16%on the first day,98.4%on the 11th day and 99.02%on the 28th day;the release of available potassium was 56.96%on the first day,98.67%on the ninth day and 99.24%on the 28th day.The fertilizer had a certain slow-release effect.The fertilizer effect test of Chinese cabbage showed that the pomelo peel based compound microbial slow-release fertilizer group improved the soil p H,increased the soil water content by 28%,increased the soil organic matter by 15%,increased the soil available nitrogen,available phosphorus and available potassium by 861%,545%and140%,increased the soil peroxidase activity,urease activity and sucrase activity by 16%,90% and 1303% respectively,and increased the soil microbial biomass by 210%.Compared with the control group,the fresh weight of Chinese cabbage increased by659%,chlorophyll and vitamin C increased by 625%and 231%,catalase activity,peroxidase activity and superoxide dismutase activity increased by 107%,61%and 1%,and total nitrogen,total phosphorus and total potassium increased by 179%,112%and504%.Pomelo peel based compound microbial slow-release fertilizer effectively improved soil fertility and the yield and quality of Chinese cabbage.The results show that the pomelo peel-based compound microbial slow-release fertilizer is a kind of biological organic fertilizer with slow-release effect.The preliminary fertilizer effect is obvious,which makes it worthy of further promotion and demonstration.In so doing,this study can provide certain solutions for realizing the comprehensive resource utilization of pomelo peel and reducing the environmental problems caused by excessive use of chemical fertilizers. |
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