Effects Of Long-term Fertilization On Soil Fertility, Organic Carbon Pools And Soil Aggregation In Paddy Soil And Upland Red Soil

Along with the global warming and the development of modern agriculture, the problems of environmental degradation and resource scarcity have been more prominent, in order to keeping the quality of soil conservation and the sustainable use of soil resources the study of soil fertility quality, soil organic carbon pools and soil structure has become an important research field. In this study, paddy and upland red soils which derived from quaternary red clay had been chosen as the research materials. Affected by different patterns of fertilization, long-term fertilization plots are located in Jiangxi Provincial Red Soil Research Institute, the soil fertility quality, soil organic carbon pools distribution and turnover rates, stability of soil aggregates and the effects on soil aggregate stability were investigated. Thereby, it is meaningful to guide the agricultural production, strengthen the farmland nutrient management and finally realize the sustainable development of agriculture.The main results are showed as follows:(1) The long-term fertilization treatments significantly affected the properties of soil. The long-term application of N fertilizer may lead to soil acidification. In upland soil the soil pH values were significantly lower than in paddy soil. Only the NPKOM treatment effectively inhibited the soil acidification and significantly improved soil fertility quality. The SOC content of all treatments increased as a result of stubble and organic fertilizer remaining in the fields since the beginning of the experiment. Therefore, the combined application of inorganic and organic fertilizer is benefited for enriching soil nutrients and the sustainable development of agriculture.(2) The results of evaluating on the soil fertility quality by use of the Fuzzy comprehensive assessment showed:The NPKOM treatment in paddy soil and upland soil belonged to2grade and others were in the3grade. The upland soil under NPK,2NPK treatment belonged to3grade, and others were in the4grade. However, the fertility quality of upland soil was lower than paddy soil. The results described above illustrated that the application of chemical fertilizer plus organic manure will enhance the soil fertility quality in two soils. The quality of single application of N fertilizer had a decreasing trend on both soils.(3) The land use and long-term fertilization significantly changed the composition of POM associated C pools (cPOM、fPOM and iPOM_mM). The C conten of mM accounted for60%in paddy soil whereas the mineral associated C was mainly in upland soil. Through59days laboratory aerobic incubation, the cumulation of CO2-Ct followed the order of microaggregate, original soil and silt clay. The half-life of upland soil was larger than paddy soil, however, soil organic carbon pool turnover rate is slower. Therefore, the application of organic fertilizer can increase soil organic carbon pool turnover rate, and promote to update soil organic carbon pool. In the two ecosystems, the results showed a growing exponentially positive correlation between soil carbon sequestration and SOC input. The higher carbon sequestration efficiency (ΔSOC/ΔC input) and SOC pools in paddy soil explained that organic matter mineralization rate is relatively low under flooded. Apparently, microbial activity in anaerobic conditions is lower than in aerobic conditions.(4) In this paper, we chosed three long-term fertilizer treatments (CK, NPK and NPKOM) of the paddy soil and upland soil to study the formation mechanism of soil aggregates. After extracting from four treatments (Water treatment, Oxalate treatment, DCB treatment and H2O2treatment), throgh discussing the contents of organic carbon, iron and aluminum oxides and specific surface area, the results showed:at0.053-0.25mm level, free iron and aluminum oxides instead of organic matter acted as the main cementing substance of soil aggregates in paddy soil. Unlike paddy soil, in upland soil the main cementing substance was organic matter at0.25～2mm level or iron and aluminum oxides at0.053～0.25mm level.At<0.053mm level, iron and aluminum oxides were the main factors of specific surface area.(5) The biomass of different organs of rice and maize were affected by different fertilization patterns. Overall, The grain yield of rice biomass accounted for more than50%. Compared with CK, only single application of P fertilizer could improve rice grain yield among one-factor fertilization. The results revealed that P fertilizer has played an important role in raising grain yield and biomass of straw and stubble. NPKOM treatment significantly improved crop biomass and promoted system productivity. Maize straw biomass of total biomass accounted for about50%. The maize biomass is the lowest under the application of N fertilizer, indicating that the application of N fertilizer may decline the production of maize.The SOC and alkalized N reached extremely significant level with all organs of maize. Total P and available P has a significantly impaction on aboveground biomass. From the point of nutrient uptake of crops, N and P uptake of rice and maize were mainly absorbed in grains, and K nutrient was in straw.