Physiology-based crop management for yield maximization of hybrid rice

摘要

High grain yield of hybrid rice is attributed to high vegetative biomass production, high leaf area, large panicles, and, in some cases,high tillering capacity. Crop management strategies based on physiological characteristics of temperate hybrid rice have been developed to maximize yield in China. Early growth of temperate hybrids is promoted by proper seedbed management, plant spacing, and nutrient supply. Unproductive tillers are controlled by proper timing and rate of N application and by mid-season drainage or deep irrigation.Nitrogen topdressing based on leaf N status is practiced to regulate canopy size and architecture. Nutrient and water management even during late grain filling and delayed harvest is important for improving the grain filling of temperate hybrid rice. Hybrid rice has recently been released for commercial cultivation in the tropics. Crop management practices used for conventional rice are also commonly used in tropical hybrid rice. Knowledge is limited on management strategies to maximize yield of tropical hybrid rice. The methods developed to maximize yield of temperate hybrid rice cannot be adopted for tropical hybrid rice. In 1992, IRRI began research on crop management of hybrid rice, especially N management for tropical hybrid rice based on physiological characteristics.Applying N at the basal and mid-tillering stages improved biomass production and sink size for both the tropical hybrid and the inbred cultivar. As sink size increased, however, the grain filling percentage of the inbred cultivar declined more than that of the tropical hybrid. Therefore, the tropical hybrid responded more to N application at the basal and mid-tillering stages than the inbred cultivar.Application of N at flowering ncreased leaf N concentration, Rubisco content, and photosynthetic rate in flag leaves. The grain filling percentage and yield of tropical hybrid rice were improved significantly by late-season N application. The inbred cultivar did not respond to N application at flowering in terms of grain yield. Rectangular planting and increased hill density improved sink size and grain yield only in hybrid rice. These results suggest that crop management strategies should be developed based on the physiological characteristics of tropical hybrids to fully express their yield potential.