Studies On Changes Of Soil Fertility In Paddy Soils With Rice Plastic Film Mulching Cultivation

Compared with traditional flooded cultivation and uncovered cultivation, the fertility characters of paddy soils with plastic film mulching cultivation were studied in this paper. The results were as follows:Compared with conventional flooded paddy soils, rain fed and mulching plastic film slightly reduced bulk density, increased total porosity of the soils. It greatly reduced the pH value of the soils and increased the cation exchange capacity of the soil. It markedly accelerated mineralization of the soils, which resulted in decreasing organic matter, total N, and total P of the soils and increasing available N, P, and K of the soils. It could increase the yields of rice.Compared with traditional flooded cultivation, film mulching cultivation reduced available N of the soils in the 0-10 cm soil layer and increased it in the 10-60 cm soil layer. It reduced available P of the soils in the shallow farming layer (0-10cm) , increased it in the middle farming layer(10-20cm ) and was almost no difference variety in the deep farming layer(20-60cm). Compared with uncovered cultivation, it increased available N, P of the soils in each soil layer. Compared with traditional flooded cultivation and uncovered cultivation, it obviously increased available K of the soils in each soil layer of most experiment sites. When underground water level was lower, mulching plastic film resulted in salt accumulate in the surface layer of soils. When underground water level was higher, it caused to takes off the salt in the surface layer of soils.Compared with traditional flooded cultivation, film mulching cultivation increased available Zn in the 0-30 cm layer of soils. It reducedavailable Fe of the soils in the 0-10 cm layer, increased it in the 10-20cm layer and was almost no difference variety in the 20-60 cm layer. It reduced available Cu, Mn of the soils in the 0-60 cm layer of soils. Compared with uncovered cultivation, film mulching cultivation increased available Zn, Fe in the 0-30 cm layer of soils and reduced available Mn in each soil layer, but available Cu was almost no difference.Under higher temperature and less rainfall circumstance during early growth stage of rice in plain, film mulched cultivation increased available N, P of the soils in early growth stage and reduced them during late growth stage. Film mulching cultivation increased soil available K during early growth stage, reduced it during middle growth stage, and slightly increased it after harvesting. The soil salt contents were increased in all growth stages of rice with film mulching cultivation, especially in panicle initiation stage and harvesting stage.