Nutrient uptake requirements with increasing grain yield for rice in China

Improved estimates of nutrient requirements for rice (Oryza sativa L.) in China are essential to optimize fertilization regulation for increasing grain yields and reducing the potential of environmental negative influences, especially under high-yielding intensive systems. A database involving rice grain yields, nutrient concentrations and accumulations collected from on-field station experiments in the literatures published from 2000 to 2013 in China was developed to understand the relationships between grain yields and plant nutrient uptakes, and to quantify nutrient requirements for different yield levels. Considering all data sets, rice grain yield ranged from 1.4 to 15.2 t ha−1 with the mean value of 7.84 t ha−1, and ca. 10.4% of yield observations were higher than the yield barrier level of 10 t ha−1. N requirement to produce one ton grain was 21.10 kg for the yield range <4.0 t ha−1 with a high variation of 45.8%. Except of the yield range <4.0 t ha−1, the values of N requirement, firstly increased from 18.78 kg for yield range 4.0-5.5 t ha−1 to 20.62 kg for yield range 7.0-8.5 t ha−1, then decreased slightly to 19.67 and 19.17 kg for the yield range 8.5-10 and >10 t ha−1, respectively. Phosphorus (P) and potassium (K) requirements showed increasing trends, from 3.51 and 19.87 kg per t grain for <4.0 t ha−1 yield range to 4.10 and 21.70 kg for >10.0 t ha−1 range. In conclusion, nutrient requirement varied with increasement of grain yield, and N, P and K presented various response trends, increasing, declining or stagnating, which would be of great benefit for improving fertilizer strategies.