Integrated nutrient, water and other agronomic options to enhance rice grain yield and N use efficiency in double-season rice crop

Abstract Options to increase resource use efficiency and climatic yield potential of locally adapted super rice hybrids including combined water, nutrient and other agronomic management are limited. Hence, the aim of our three-year (six seasons) experiments during early-season (ESR; Luliangyou996) and late-season (LSR; C-liangyou396) rice in southern China was to identify key yield parameters and optimum resource use options to enhance the crop's climatic yield potential. Grain yield averaged across all three years with effective N management combined with post-anthesis shallow wetting and drying was 32.8% and 37.1% higher than the normal farmers’ practice in Liuyang County in ESR and LSR, respectively. More spikelets m −2 were the key to achieving high yield potential, further supported by increased leaf area index and high radiation interception and internal use efficiency. The split application of nitrogen in combination with shallow wetting and drying allowed for better N uptake, use efficiency and partitioning, leading to enhanced biomass and yield. The high yield potential, however, was not just a function of genetics and management but also depended on the climatic conditions prevailing, particularly temperature and radiation. In ESR, lower temperature during vegetative stage reduced overall biomass and sink size while subsequent higher temperature reduced the total grain filling period by 17 days compared with LSR, indicating a climatic condition-driven decline in yield potential rather than lower genetic potential of the super hybrids. A lack of correlation of spikelets panicle −1 and spikelets m −2 with grain-filling percentage in LSR provided evidence that a larger sink does not necessarily result in poor grain filling when sufficient time and assimilates for grain filling are provided, which is more climate dependent. Our work highlights the benefits of integrating nutrient, water and agronomic management options to achieve high NUE and grain yield.