Effects of planting time and cultivar on dry matter yield and estimated total digestible nutrient content of forage rice in southwestern Japan

We examined the effects of planting time and cultivar on dry matter yield of forage rice in southwestern Japan. The cultivar Tachiaoba produced a 81.1% higher dry weight per tiller but a 40.5% fewer tillers per square meter than Hinohikari, thus producing a 9.0% higher dry matter yield. Nishiaoba produced almost the same dry matter yield as Hinohikari. Early transplanted plants produced a 14.9% higher dry matter yield and a 21.1% higher dry weight per tiller than normally transplanted plants. Early transplanted Tachiaoba produced the highest dry matter yield in the experiment. We also examined the effects of planting time and cultivar on estimated total digestible nutrient (TDN) content. The estimated TDN content in panicles was 27.0% higher than that in leaf sheath plus stem and 31.1% higher than that in leaf blades. Tachiaoba and Nishiaoba, which had 5.2% and 4.2% lower ratios of panicle to total dry weight than Hinohikari, respectively, had a 2.0% lower estimated TDN content in the whole plant than Hinohikari in 1 of the 2 years. However, early transplanted plants, which had a 5.9% lower ratio of panicle to total dry weight than normally transplanted plants, had a 0.6% higher estimated TDN content in the whole plant than normally transplanted plants. Early transplanted plants had a 4.7% higher estimated TDN content in leaf sheath plus stem than normally transplanted plants. These results suggest that early transplanted plants had a higher estimated TDN content in the whole plant than normally transplanted plants because of the higher estimated TDN content in leaf sheath plus stem. Tachiaoba produced a 9.1% higher estimated TDN yield than Nishiaoba and a 7.7% higher than Hinohikari. Early transplanted plants produced a 16.1% higher estimated TDN yield than normally transplanted plants. Early transplanted Tachiaoba produced the highest estimated TDN yield in this experiment. Therefore, it is effective to plant Tachiaoba early to obtain high dry matter and estimated TDN yields.