A comparison of the effects of controlled release urea, stable urea and microorganisms increasing double rice yield and nitrogen use efficiency

【Objectives】 China is the largest producer and consumer of rice(Oryza sative L)in the world. Nitrogen is the most essential element for rice production, however, low nitrogen use efficiency(NUE)has been existed. New nitrogen fertilizers(controlled release urea, nitrification inhibitor and microbial inoculant) were developed to solve this problem. Their effects were compared in this paper to provide reliable basis for the fertilizer promotion in rice cultivation. 【Methods】 Five different fertilizer treatments, CK: conventional urea, CRU: polymer-coated controlled release urea, NU: urea containing nitrapyrin, DMPP: urea containing nitrification inhibitor 3,4-dimethylpyrazole phosphate, and EM: microbial inoculant combined application with urea were set for conducting a two year field experiment(2012-2013)in Jingzhou city , Jianghan Plain, Central China. Effects of different fertilizers on growth(plant height, chlorophyll, tiller and spike numbers), yield(grain numbers, setting rate, 1000-grain weight, straw and grain yield)and NUE(nitrogen recovery efficiency, nitrogen agronomic efficiency, nitrogen physiological efficiency)were explored. Increases in yield and NUE caused by different fertilizers were synthetically analyzed, and their seasonal fluctuations were also discussed. 【Results】The new fertilizers contribute to the increases of rice plant height, chlorophyll concentration, tiller numbers, spike numbers, grain numbers, setting rate and 1000-grain weight, and ultimately improve the straw and grain yields effectively. Compared with CK, CRU achieves the highest and most stable yield increase by 18%(P0.05)in both early and late rice, and DMPP, NU and EM achieve a yield increase by 14%(P0.05)in late rice, no significant increases in early rice. Better growth and yield promotion is showed in late rice than in early rice. The new fertilizers raise the nitrogen recovery efficiencies significantly compared with CK(35%). The nitrogen recovery efficiencies of CRU and NU reach to 53% and 47%, respectively. With the combined application of microbial inoculant, it presents a higher nitrogen recovery efficiency, which reaches to 55% and is very significant higher(P0.01)than that of late rice under CK in 2013. The nitrogen agronomic efficiencies of the new fertilizers are higher than that of CK at different levels, among which CRU is very significant higher(P0.01)than CK in 2013. The nitrogen physiological efficiencies of the new fertilizers are lower than that of CK, except that DMPP is higher than CK in 2013, but there exists no significant difference. 【Conclusions】 The application of controlled-release urea, nitrification inhibitor and microorganisms in paddy field get remarkable rice yield increases and NUE promotion significantly. The beneficial effect is in order of controlled release urea higher than stable urea and higher than combined application of microbial inocul urea.