Effect of sowing time and nitrogen on rice cultivars of differing growth duration in New South Wales 2. Biomass production and partitioning

Abstract

In New South Wales, rice cultivars with shorter growth duration are sought to reduce water use and to increase the efficiency of rice production. We examined the biomass accumulation of a short-duration cultivar in comparison with 3 long-duration cultivars across a range of sowing time and nitrogen treatments. The biomass accumulation of the short-duration cultivar was smaller than that of the long-duration cultivars, but the yield potential was similar. This was achieved by the production of similar number of florets per m2, despite smaller biomass at flowering, and greater harvest index. Only early-sown treatments resulted in smaller yield of the short-duration cultivar due to restricted biomass accumulation and floret production. A simple biological model of post-anthesis growth, which included the effect of low temperature, predicted growth with an accuracy similar to that of the measurements. The low temperature function assumed growth stopped following a daily minimum temperature below a specified threshold, and the number of days without growth was a function of the severity of the temperature. We concluded that the yield of short-duration cultivars may be less stable when stress occurs during grain filling because there is less biomass at anthesis and, therefore, less reserve available to fill the grain.