Effects Of Large-scale Cattle Manure Composting Technology On Nutrient And Water Content Changes And Harmful Gas Emission

Composting process is to transform organic matter in livestock manure into decomposed materials with the help of various microorganisms in the manure,which can effectively improve the environment,reduce water and air pollution,and supplement sufficient nutrients and organic matter for the soil.Static composting,aerobic composting（turning over regularly）,film mulching composting and mixed composting（turning over regularly）are four widely used composting technologies at present.At present,there is still a lack of relevant research on the quality of organic fertilizer and harmful gas emission in different composting methods.In order to explore the effects of different composting processes on the maturity of compost,the loss and retention of nutrients and the emission of greenhouse gases and ammonia,an outdoor composting experiment was conducted with cow dung and corn stalk as raw materials for 71 days.The main research results are as follows:（1）The highest temperatures of T1（composting）,T2（composting+dumping）,T3（composting+film mulching）and T4（turning+film mulching）were 67.70,70.13,63.12,67.18℃,respectively,and the duration of high temperature period（>55℃）was 11,11,4 and13 days,respectively,all of which met the technical specifications of livestock manure composting.The temperature of T2（composting+dumping）and T4（turning+film mulching）treatments increased on the second day after turning,the materials were fully mixed,and the organic matter was degraded again.The heat preservation of T4（turning+film mulching）was better than that of T1（composting）treatment because of film mulching,and the temperature increase was more significant.（2）At the end of composting,the p H value of the treatment without film mulching was low,and the turning effect had no significant effect on p H value.The final EC values of each treatment are 3.09,3.11,2.95,2.96 m S/cm,respectively.Plastic film mulching will reduce the EC value of materials,but the decrease is not significant.Turning and throwing will accelerate the loss of water in the manure,and film mulching treatment will have better water retention.The effects of plastic film mulching and turning were not significant on C/N,GI,fecal coliforms and mortality of ascaris eggs.Turning and throwing will promote the reduction of volatile solids,and all treatments will meet the requirements of harmlessness.（3）During composting,CO₂emission mainly concentrated in the first 15 days.Although plastic film mulching and turning treatment can improve the emission rate of CO₂,they have no obvious influence on the total emission.The emission of CH₄is mainly concentrated in the cooling period,and the emission rate of CH₄is always kept at a low level in the high temperature period.Turning and throwing will make air enter,thus inhibiting the production of CH₄.N₂O emission is mainly concentrated in the first 8 days,and turning is beneficial to the generation and accumulation of N₂O,and plastic film mulching will delay the peak of N₂O emission rate and reduce the peak.T4（turning+film mulching）treatment has the largest cumulative emission of NH₃,and turning and film mulching promote the emission of NH₃.（4）Among the four treatments,T2（composting+dumping）and T3（composting+film mulching）have the highest and lowest warming potential,respectively,and dumping can enhance greenhouse gas emissions,and film mulching can effectively reduce greenhouse gas emissions.On the whole,T3（composting+film mulching）has the lowest warming potential,only19,145.52 g CO₂-C d^-1m^-2,which emits the least greenhouse gases and has good nutrient retention,so T3（composting+film mulching）is the best treatment.