Effects Of Long-term Continuous Cropping On Cotton Growth And On Cotton Field Soil Biological Activity

The cotton is an important crop in Xinjiang area, since the cultivated area is large and the continuous cropping time is long , there are a series of negative influences, which caused continuous cropping questions of cottons in Xinjiang to be prominent. This experiment simulates cottons long-term continuous cropping through fixed-point micro area experiment, the influence of growth, the important physiology characteristic and so on to show up the continuous cropping influence on the growth of the cotton. The experiment also shows that the influence of soil biological activity by studying main soil microorganism class group, and shows that soil enzyme activity changes in different continuous cropping ,and the continuous cropping influence on the soil biological activity by contrasting the field with activated charcoal processing to the field without it as well as the coordinate straw stalk. In order to reduce the continuous cropping barrier, the experiment establishes the scientific cultivation system, which provides the theory basis to the high quality and continuouce production of Xinjiang cotton.The main results are as follow:1. The long-term continuous cropping has the obvious adverse effect on the cottons growth, and some cotton important physiology target has been influenced by the continuous cropping barrier in the different continuous cropping age. Consequently, the output of cottens has reduced,the root activity and the chlorophyll falled along with the continuous cropping, While the SOD and the POD activities of the roots and leaves and the content of MDA have the varying rised in the different period of duration. the SOD and POD activities and the content of MDA with the activated charcoal adding have the varying degree drop contrast to that has not added activated charcoal while the root activity and the chlorophyll have the distinct enhancement .By test the physiological target we can know that the cotton continuous cropping soil can causes the harm to cotton's growth and the output, but with the activated charcoal adds to the soil it can reduce the adverse effect which caused by the cotton continuous cropping .2.When the continuous cropping cotton field soil adds the activated charcoal, the urease activeness in soil reducing with the continuous cropping.The soil with urease activities that processed by activated charcoal has the ascension slightly compared to the soil without it. The urease activities of treatment 5+C, 10+C and 15+C in buding elevates 11.4%,7.2% and 0.3% compared to that without the activated charcoal,which explained that in buding after adding the activated charcoal, the short-term continuous cropping can obviously enhance the soil urease activites; after joining the activated charcoal the invertase activity in the long-term continuous cropping improves more obviously than the short-term continuous cropping. When the soil adds the activated charcoal, the catalase activites reduces along with the continuous cropping age.The influence of the activated charcoal on the catalase active is little ,and can't improve the the soil condition obviously; The soil with the activated charcoal dosen't influence the peroxidase activitives obviously.3.In the seedling stage the number of the bacterium reduces when the soil adds the activated charcoal, and in the later birth period besides the long-term continuous cropping, the the soil with the activated charcoal enhances the number of the bacterium in the soil.In the different period ,the soil bacterium number of every treatments reducing after first elevating. In the cotton's buding it is highest, and in the boll opening time it is the lowest. The fungi number with the activated charcoal in the later period can reduces the fungi number obviously, and reduces continuous cropping question because of the the cotton fungi. In the whole period the fungi number is highest in the seedling stage while reduces in buding and rises in flowering, the fungi number is lowest in the boll opening. The number of actinomyce in the soil has no regular changes after adding the activated charcoal.4. The urease activites drops firstly and rises lately along with the continuous cropping after returning cotton stalk to field . the urease activines assumes the drop tendency when not surpass for 15 years while rise surpasses for 15 years ;The Invertase activities is lowest by the continuous cropping 10 years afterlong-term continuous cropping Invertase activities strengthens, the soil condition tends to the change for the better, is advantageous in cotton's growth ;Catalase activeness reduces first after the continuous cropping and rise laterly, when the continuous cropping is shot the catalase activeness is low, the peroxide decomposition is blocked, and affects the cotton's growth, when the continuous cropping surpasses 10 year catalase activeness ascension, speeds up the decomposition peroxide, and advantageous in reduces the peroxide poisons the function to the soil and the biology; returning stalk also field processing along with the continuous cropping, the peroxide enzyme activity assumes the trend of escalation.