Population Characteristics of Super <I>Japonica</I> Rice Ningjing 1 and Ningjing 3 and Its Responses to Nitrogen

Abstract

In order to study the super high-yielding population characteristics of super japonica rice and its responses to nitrogen, two field experiments with five N rate treatments and four N application ratio treatments of Ningjing 3 were carried out in 2008, the 6.7 ha demonstration fields of Ningjing 1 and Ningjing 3 in 2007 and 2008 were also investigated. Results showed that the dry matter accumulation of Ningjing 1 and Ningjing 3 after heading was 70–80% of the grain yield, and the apparent translocation ratio of dry matter from stem and leaves to grain was small, which resulted in the high and stable grain yield. Ample spikelets per square meter were the guarantee of super and stable high yield. To achieve the target yield of 11.0 t ha?1, the spikelets per square meter must be above 42 000 m?2; to achieve the target yield of 11.7 t ha?1, the spikelets per square meter must be above 45 000 m?2, as well as grain filling rate and grain weight must be above 90% and 26 mg. For super high-yielding rice population, the op- timal LAI at heading should be 7.0–7.5, crop growth rate (CGR) from heading to maturity should be higher and the harvest index (HI) should be above 0.5. The appropriate N rate and relative more N topdressed at panicle initiation stage could not only ensure the optimal LAI at heading, but also maintain the plant type characteristics of super high-yielding rice, improve the LAI after heading, leaf area duration, CGR and HI, therefore achieve the super high grain yield.