Effects of Rapeseed Straw Returning on Increment of Yield and Supplying Capacity of Potassium in Rice

The effects of rapeseed straw returning on yield and potassium uptaking of rice were studied in the four counties including Yingcheng Xiaochang, Hanchuan, and Jingmen of Hubei province. Potassium fertilization had significant effects in Yingcheng, Xiaochang and Jingmen site. The yield and straw biomass of rice averagely increased 725 and 669 kg / hm2 in the straw returning with treatment(NP+S) compared with no potassium fertilization(NP) with the increase rate of 10.21% and8.36%. The K uptaking was improved by applying potassium fertilization or straw returning over all sites. Compared with NP treatment, the K uptake increased 20.2, 48.3 and 58.3 kg K2 O / hm2, in the NP +S, NPK and NPK +S treatments. The increase of rice potassium uptaking was due to the increase of biomass. The differences of K content were not significant among the treatments. Soil available K content declined in all treatments among the sites after planting rice. The decline was significantly lower in the treatment of straw returning compared with treatments without straw returning. It is indicated that rapeseed straw returning can improve the yield of rice grain and straw, enhance the K supplying and relieve the deficiency of soil potassium.