Accumulation and utilization of nitrogen, phosphorus and potassium of irrigated rice cultivars with high productivities and high N use efficiencies

In the iiangsu province of Southeast China, high irrigated rice yields are supported by high nitrogen (N) fertilizer inputs and low fertilizer N use efficiencies. A little attention has already been paid to the combined increase of rice yield and N use efficiency, however, the accumulation and utilization of N, phosphorus (P) and potassium (K) of irrigated rice genotypes with high yield and N use efficiency is still obscure. Field experiments were conducted in 2010 and 2011 where two cultivars with low productivity and low N use efficiency (LPLNE), two cultivars with high productivity and medium N use efficiency (HPMNE) and two cultivars with high productivity and high N use efficiency (HPHNE) were grown separately under their respective optimum N application to achieve maximum attainable yields. Accumulation and utilization of N, P and K as well as their interacting relationships were studied. The results showed that: (i) When values were averaged across cultivars and years, compared with LPLNE, HPMNE and HPHME showed 18.1, 25.3, and 9.6% higher N, P, K accumulations at maturity, respectively. The N grain production efficiency (NGPE) and K grain production efficiency (KGPE) were both higher, although P grain production efficiency (PGPE) showed no consistent tendencies; (ii) When values were averaged across cultivars and years, in comparison with HPMNE, HPHNE achieved a 1.7% lower total N accumulation, but a 6.5% higher N accumulation during the period from heading to maturity. At maturity, N accumulation in leaves increased by 3.5% and that in grains decreased by 4.0%. Total P and total K accumulation increased by 2.5% and 2.8%, respectively, which was mainly attributed to greater accumulation after panicle initiation, especially in the period from heading to maturity. At maturity, P accumulation in leaves increased by 11.5% and that in stems and grains did not differ significantly, K accumulation in stems increased by 4.2% and that in leaves and grains did not differ significantly. The N, P and K accumulation in grains at maturity did not explain the higher N use efficiency of HPHNE. This study suggested that a decrease of N accumulation before panicle initiation and increase of N, P. K accumulation during the period from heading to maturity may be helpful to combine the high yield and high N use efficiency in rice. (C) 2014 Published by Elsevier B.V.