Decomposition Regularity Of Rice Straw Returning To Soil And Its Effect On Soil Nutrients And Enzyme Activity

Straw returning is the most straight and valid path of effective utilization straw resource, straw returning is the important path for agricultural sustainable development, which can return most nutrition from crop absorbing to soil. Plot experiment and pot experiment were used in the test, effect of nutrition releasing regularity of rice straw returning on soil nutrition content and rice yield were researched, The results showed that:Straw decomposition amount during the first breeding season was higher than that during the second breeding season after straw returning, straw decomposition rate was53.67%during the first breeding season, which was14.07%during the second breeding season, straw decomposition amount was seldom during harvest of the first breeding season to land preparation of the second breeding season. The order of N, P, K and C releasing rate was:K>P>N≈C.Inorganic nitrogen of soil solution decreased gradually as the rice grew, inorganic nitrogen presented a significant peak after topdressing urea. Straw returning decreased inorganic nitrogen of soil solution decreased, however, NH4+-N increased, and decreased slowly as the rice grew; NO3--N of soil solution decreased, and rate of decay presented fast-slow, topdressing urea could increase NH4+-N and NO3--N of soil solution. P content of soil solution was low, the regulation was that decrement was large in prophase and small in anaphase. K content of soil solution decreased gradually as the rice grew, and decreased rapidly in metaphase. K content increased significantly with straw returning.There was significant effect of continuous straw returning on soil nutrition. Continuous straw returning increased organic matter content, average increasing0.241g/kg per year, and the content of total-N, NO3--N and NH4+-N were increased, continuous straw returning had no significant effect on total-P and available-P of soil, while continuous straw returning significantly increased total-K and available-K of soil, and K content increased with straw returning amount increasing.There was effect of straw returning on enzyme activity of soil. The trend of Urease enzyme activity was increase-decrease-increase during the whole sampling stages, average activity of Urease enzyme with straw returning was445.5mg (g·d)-1, which was lower28.1%than not straw returning570.5mg (g·d)-1. Invertase enzyme activity was increased then decreased, and invertase enzyme activity of first three sampling were higher than other sampling stages, then which change was not significant; average activity of invertase enzyme with straw returning was20.2mg (g·d)-1, which was higher19.8%than not straw returning16.2mg (g·d)-1. The activity of acid phosphatase enzyme was larger fluctuation with straw returning, the maximum was at8.21, the minimum was at9.1, the difference of enzyme activity was over200mg (g·d)-1, enzyme activity with not straw returning presented decrease-increase-decrease, and the difference of average activity was small with straw returning. Regularity of catalase enzyme activity was the same between two treatments during the whole sampling stages, which was decreased then increased, and had no significant difference.Straw returning had effect on rice yield. There was not significant effect on rice yield when straw returning amount was lower than80g/pot (12500kg/hm2); there was negative effect on growth and yield when straw returning amount was80-160g/.pot, rice yield was significantly decreased with straw returning amount increasing.