Study on high efficiency nutrient use and regulation of soil nutrient dynamics for high yield rice

This long-term project, started in 2005, is being implemented by the Soil and Fertilizer Institute, Hunan Academy of Agricultural Science. The objective is to collect and compile all the relevant information on N in relation to rice cropping and it's environmental impact to improve the efficiency of rice production. In 2012, a summary of results collected in recent years (2005 to 2012) from the analysis of 2,367 field experiments was prepared. Partial factor productivity (PFP), agronomic efficiency (AE), apparent recovery efficiency (RE), and physiological efficiency (PE) of early rice, late rice, and middle-season rice varieties in Hunan province were calculated.

The effect of applying N, P and K fertilizers on yield of early rice, later rice and middle-season rice was investigated over seven paddy soil areas. Results showed that the average contribution rates of soil nutrients to early rice, later rice and medium rice were 65, 62 and 59%, respectively. Mean yield increases with N, P and K applications to early rice, late rice and medium rice were 20, 11 and 9%; 20, 9, and 9%; and 15, 7, and 8%, respectively. The critical indices of alkali-hydrolysable N, Olsen-P, and available K for rice were 120, 7 and 60 mg/kg. In general, the maximum fertilization rates to early rice were 201 kg N/ha, 96 kg P₂O₅/ha and 120 kg K₂O/ha, while the economic fertilization rates were 148 kg N/ha, 53 kg P₂O₅/ha and 60 kg K₂O/ha. Similarly, the maximum fertilization rates to later rice were 203 kg N/ha, 80 kg P₂O₅/ha and 135 kg K₂O/ha, while the economic fertilization rates were 150 kg N/ha, 43 kg P₂O₅/ha and 62 kg K₂O/ha. The maximum fertilization rates to middle-season rice were 165 kg N/ha, 98 kg P₂O₅/ha and 121 kg K₂O/ha, while the economic fertilization rates were 122 kg N/ha, 49 kg P₂O₅/ha and 49 kg K₂O/ha. PFPs of N, P₂O₅ and K₂O for rice crops were found to be 48, 122 and 87 kg/kg, respectively; while AEs of N, P₂O₅ and K₂O were found to be 11, 12 and 9.7 kg/kg, respectively; and REs of N, P₂O₅ and K₂O were found to be 32, 12 and 36%, respectively. Hunan-16