2017 Volume 86 Issue 3 Pages 267-275
Effects of sowing date on the yield, quality and palatability of rice cultivated by non-tillage direct sowing were investigated using the leading medium ripening varieties in Kagawa prefecture “Koganemasari”, “Oidemai”, and “Hinohikari”. The sowing dates were April 23, May 7, and May 21, in plot I, II and III, respectively. For comparison, “Koganemasari” was transplanted on June 10. Yield was highest in plot I followed by plot II and plot III in this order. On the other hand, the overall eating-quality in the sensory test compared with that in the transplant plot of “Koganemasari” was highest in plot III followed by plot II and plot I in this order. The ratio of whole grain to above-ground biomass was highest in plot II followed by plot III, and lowest in plot I. The effects of sowing date were determined by the average temperature during the period from heading to maturity (ripening temperature) of the respective sowing plots. That is, the ripening temperature in plot III was 21.4～22.4ºC which is near the suitable temperature for high yield (22ºC), but is lower than the suitable temperature for high palatability (25ºC). Thus, in plot III, the yield was high but palatability was low. The ripening temperature in plot I was 24.2～24.5ºC which was suitable for eating quality but higher than the suitable temperature for yield. Thus in plot I palatability was high but yield was low. Furthermore, grain appearance was inferior in plot I because the ripening temperature exceeded 24ºC, which increases the occurrence of immature grain. Therefore, considering yield, quality of grain, appearance and eating quality comprehensively, the optimum sowing time in non-tillage direct sowing culture in Kagawa Prefecture was considered to be around the sowing date of plot II in this experiment which was 20～14 days earlier than the currently practiced sowing time.
