Research On Soil Organic Carbon Fractions Changes Of Continuous Cropping And Straw Incorporation Cotton Field

Xinjiang is the largest cotton planting region in China and accounts for about 70% of the suitable area for cotton cultivation, which even reaches 95% in some cotton cultivation locations, resulting in the large of continuous cropping area, long period of continuous cropping, the prominent problem of continuous cropping. Long-term continuous cropping can produce continuous cropping obstacle, led to soil borne disease aggravated, the decline of soil fertility, crop failures and other issues. Straw incorporation not only can improve soil fertility, nutrient and organic carbon storage,but also can improve soil structure and physical properties. However, straw incorporation exacerbate the plant diseases and insect pests, straw decomposition will release the allelochemicals so that produced autotoxicity, advantages and disadvantages coexist. Soil organic carbon and its fractions can reflect the change of soil pr operties and soil fertility, is a comprehensive evaluation indicators on the impact of field management measures on soil quality. Therefore, this paper based on the long-term continuous cropping cotton positioning exper imental field as the research object, with straw removal treatments as contrast, in order to analysis of the change characteridtics of soil physicochemical properties, active organic carbon fractions and the changes of the content of humus component of long-term continuous cropping cotton under straw incorporation conditions.The result was shown as follow:1.Straw incorporation declined soil BD of three soil layers of long-term continuous cropping cotton field, soil BD decreased gradually with the increase of continuous cropping years, and soil BD increased with the increase of soil depth; straw remove soil BD increased with the increase of soil depth and continuous cropping years.Straw incorporation reduced the continuous cropping cotton soil p H value, was conducive to the growth of crops. Long-term continuous cropping and straw incorporation cotton soil p H value with the increase of continuous cropping year showed a change trend of decreased first and then increased and after decreased gradually, reached the maximum when the continuous cropping for 15 years, the soil p H value began to decline signif icantly 15 years after, straw removal treatments soil p H values increased with the increase of continuous cropping years. Straw incorporation treatments three soil depth EC value overall were rising gradually with the increase of continuous cropping years, and straw incorporation treatments soil EC were significantly higher than straw removal treatments.2.Compared with straw remove cotton field, straw incorporation signif icantly improved the three so il layers SOC, LOC, SMBC and the content of SOC, LOC, SMBC with the increase of continuous cropping years gradually increased. Straw incorporation cotton field SOCD,(LOC/SOC)%, CPMI and q MB gradually inproved with continuous cropping years increasing. Straw incorporation cotton field SOCD and CPMI rapidly increased with the increase of planting years in linear growth in 0~20 cm soil layer, 20~40 and 40~60 cm soil layer in cm soil layer of SOCD and CPMI first slowly increased and then the rapid increase with the increase of planting years in an exponential growth. Straw removal cotton SOCD,(LOC/SOC)%,CPMI and q MB decreased along with the continuous cropping years increasing. Soil organic carbon content, easily oxidized organic carbon content, microbial biomass carbon, soil organic carbon density, carbon pool management index, microbial quotient difference between the three layers decreased with soil depth increasing.3.Straw incorporation could signif icantly increase HA, HM content of three soil layer, and the soil fulvic acid content is maintained at a stable level, HA, HM content increased gradually with continuous cropping years increasing. Straw incorporation cotton field HA were predominat, straw removal cotton field FA were prevailing. Straw incorporation could signif icantly improve the CHA/CFA and PQ values compared with straw removal, CHA/CFA and PQ values gradually increased with the increase of continuous cropping years, especially after continuous cropping 15-year cultivation straw incorporation effect was remarkable.