Effects Of Organic Manure Substitution And Bio-fertilization In Upland Red Soil

With the increasing use of chemical fertilizers,several soil problems such as decline in fertility,soil compaction and decreased biological activity are becoming more and more serious,which is not only impeding the sustainable development of agriculture in China,but is also deviating the development direction of modern ecological agriculture.Meanwhile,the improper disposal of crop stalk,livestock manure and poultry manure in rural agricultural production causes terrible waste of natural resources;the burning of straw and the arbitrarily discard of manure would cause air and water pollution separately.As a traditional manner on improving soil fertility in China,organic fertilization could utilize the discarded stalk and manure adequately,it can improve the soil fertility and avoid improper use of the resources in the same time.Organic fertilization would also reduce the costs coming from the use of chemical fertilizers,alleviate environmental pollution,enhance soil quality,and achieve the prospects of storing food underground and storing food technologically.Soil organisms,as decomposers and predators in the soil food web,are the biological carriers of material cycling and energy flow in the soil ecosystem.A large number of studies have shown that soil organisms such as earthworms,nematodes are closely connected with many other soil organisms,they can improve the soil physical and chemical properties and biological activity,moreover,the activities of these organisms will affect the soil biological community composition and promote nutrient transformation.As a functional microorganism,phosphate-solubilizing bacteria(PSB)can convert insoluble phosphorus into available phosphorus which can be absorbed and utilized by plant roots more easily,this kind of bacteria exhibits great potential for increasing the supply of available phosphorus from the soil.In southern China,the dryland red soil is not suitable for the growth of crops due to the serious degradation of soil ecological function and quality,resulting in the decline of crop yield.In this study,the effects of organic manure and bio-fertilization on soil fertility,bioactivity,microbial community and the crop yield of red soil were studied.The mechanisms of organic manure and bio-fertilization on improving soil fertility were discussed.Our results will provide scientific guidance for improving fertility and restoring ecological function of red soil.The experiment was set up in Yingtan Red Soil Ecological Experiment Station of the Chinese Academy of Sciences.The treatments were:F(inorganic fertilizer),O(100%organic substitution),FO(60%organic substitution),FO+S(60%organic substitution+soil animals concentrated in situ),FO+E(60%organic substitution+earthworm),FO+P(60%organic substitution+PSB),FO+EP(60%organic substitution+earthworm+PSB).The fertility,bioactivity and microbial community function of the soil and the crop yield under different treatments were measured in the flowering stage and harvesting stage for both rapeseed and sweet potato.The results are as follows:1.Organic manure substitution and inoculation of earthworms can promote the formation of soil aggregates and enhance the stability of soil aggregates.Organic fertilizers could significantly increase the total and available contents of nutrients in red soil,while the bio-fertilization had limited effect on the total nutrients of red soil.The inoculation of earthworms could significantly increase the content of available phosphorus,available potassium and nitrate,and PSB could improve the available phosphorus significantly.2.Under different crop systems,organic manure substitution and bio-fertilization could significantly increase the total number of nematodes.The proportion of different nematode trophic groups changed in different seasons.Amendment with organic fertilizer or inoculation of soil organisms can reduce the proportion of phytophagous nematodes,inoculation of earthworms will reduce the proportion of fungivorous nematodes.Under the treatment of organic substitution,inoculation of PSB singly or composed with other soil animals can promote the colonization of PSB in the soil.Organic fertilizer and bio-fertilizers are all beneficial to enhance the biological activity of red soil(basal respiration,microbial biomass,enzyme activity).Inoculation of earthworms can significantly improve the activity of enzymes that related to C and N cycling,and phosphate-solubilizing bacteria could increase phosphatase activity.3.For the function of microbial community,organic fertilizer substitution and bio-fertilization can improve the utilization efficiency of carbon source,and inoculation of earthworms is beneficial to the utilization of amino acids,sugars and amines in soil microbes.The application of organic fertilizer could increase the abundance and evenness of microbial community in red soil,while earthworms could decrease the microbial community evenness and increase the microbial groups that use amino acids,carbohydrates and amines,which indicated that earthworm could affect the microbial community composition and function.4.Organic fertilizer substitution and bio-fertilization have a significant effect on increasing the yield of sweet potato and rapeseed,and the organic substitution and compound inoculation were the best.Although the yield of rapeseed was negatively affected by the bad weather in the second year,significant increases were still detected compared with the treatment of inorganic fertilizer.