Impacts Of Different Organic Fertilization On Soil Fertility Improvement And Its Microbiological Mechanism In Red Paddy Soil

Red paddy soil is generally characterized by low organic matter and nutrient contents,and especially in low biological fertility.Application of organic materials is an effective way to improve soil fertility and crop yield.We conducted a long-term organic fertilizer experiment in Jiangxi Province,and studied the soil basic physicochemical properties and crop yield.Furthermore,Illumina MiSeq sequencing and Microplate fluorometric protocol were applied to study and evaluate the effects of typical organic fertilization of southern China on soil microbial community and enzyme activities in red paddy soil under different fertilizations.The field experiment comprised of six treatments:?1?no fertilizer,?2?chemical NPK fertilizers?N 159kg/hm²,P₂O₅ 75kg/hm²,K₂O 142.5kg/hm² in both early rice and late rice?,?3?green manure?22500kg/hm²?at early rice,?4?double application of green manure?45000kg/hm²?at early rice,?5?green manure?22500kg/hm²?at early rice and pig manure?22500kg/hm²?at late rice,?6?green manure?22500kg/hm²?at early rice and straw returning?4500kg/hm²?at late rice,In addition,a certain amount of fertilizer?N 69kg/hm²,P₂O₅ 30kg/hm²,K₂O 67.5kg/hm²?was applied to the organic treatments every season on the basis of the application of organic materials.The main results were outlined as follows:?1?Crop yield and soil fertility were improved by long-term organic fertilizers return.The treatment of green manure at early rice and pig manure at late rice obtained the highest yield among all treatments,followed by double application of green manure at early rice,both of them were obviously higher than chemical NPK fertilizers,Besides,there were no significant difference between the other organic amendments with the treatment of chemical NPK fertilizers.The treatment of green manure at early rice and pig manure at late rice obtained the highest soil organic carbon,total nitrogen,available phosphorus and available potassium among all treatments.Compared with lower or balanced nutrition input than the chemical NPK fertilizers,other organic amendments could maintain the level of soil nutrition.Furthermore,crop yield was positively correlated with soil organic carbon,total nitrate,available phosphorus and available potassium.?2?Compared with chemical NPK fertilizers,long-term application of organic fertilizers increased soil microbial biomass and enzyme activities,among which,the treatment of green manure at early rice and pig manure at late rice was the best.Soil microbial biomass and enzyme activities were positively correlated with soil organic carbon and total nitrate,thus soil microbial carbon and nitrogen,enzyme actives could reflect the changes of soil fertility as bio-indicators.Furthermore,Soil organic carbon played a more profound influence than pH on increasing crop yield,soil microbial biomass and enzyme activities.?3?Compared with chemical NPK fertilizers,the treatment of green manure at early rice and pig manure at late rice increased the Sobs,Chao 1 and PD's diversity indexes of bacteria,and significantly changed the bacterial community structure,however,there was no significant difference between other organic amendments and chemical NPK fertilizers.Proteobacteria,Chlorflexi,Actinobacteria and Acidobacteria were the dominant phyla in red paddy soil.The bacterial communities were closely correlated with soil properties,in which soil organic carbon and available phosphorus were the most important factors in affecting bacterial community compositions.?4?Compared with chemical NPK fertilizers,organic amendments decreased the values of diversity and richness of soil fungi,and the treatment of green manure at early rice and pig manure at late rice obtained the lowest values.Beside,in comparison with other organic amendments,the treatment of green manure at early rice and pig manure at late rice also significantly changed the fungal community compositions.Mortierella was indentified as the keystone taxa,which involved in soil carbon and nitrogen cycling.Organic amendments,especially the treatment of green manure at early rice and pig manure at late rice increased the relative abundance of Mortierella.The fungal communities were closely correlated with soil properties,in which available phosphorus,total nitrogen and soil organic carbon were the most important factors in affecting fungal community compositions.In summary:Organic Amendments could increase grain yield and soil nutrient contents,improved soil microbiological indicators.Among them,the treatment of green manure at early rice and pig manure at late rice had the best effects on increasing grain yield,soil microbial biomass and enzyme activities,significantly changed the soil bacterial and fungal community structure,and increased the bacterial alpha-diversity but decreased the fungal alpha-diversity indexes respectively.