Early Planting and Early Nitrogen Application Increase Stem Total Digestible Nutrient Concentration and Yield of Forage Rice in Southwestern Japan

Abstract

The effects of planting time (early or normal), nitrogen (N) application rate (150 or 225 kg N ha^-1), and N application method (early, even, and late application of extra N) on total digestible nutrient (TDN) concentration and yield of forage rice (Oryza sativa L.) in southwestern Japan were examined. For optimal forage rice production, it is important to maximize nutritional level in leaves and stems rather than panicles because the hull restricts cattle’s ability to digest rice grain. In particular, it is important to maximize the TDN in leaf sheath plus stems (stems) which are the major part of the crop rather than leaf blades (leaves). Stem TDN yield was higher with early planting (340 g m^-2) than with normal planting (217 g m^-2) irrespective of N application rate or method. The high stem TDN yield with early planting resulted from both the high DM yield and the high TDN and organic cellular content (OCC) concentration. Stem TDN yield was not affected by the N application rate. With both early and normal plantings, stem TDN yield was higher with early N application (374 and 226 g m^-2, respectively) than with late N application (305 and 208 g m^-2, respectively). With early planting, the high stem TDN yield with method 1 resulted from both the high DM yield and the high TDN and OCC concentration. Thus, to obtain high stem TDN concentration and yield of forage rice, early planting and early N application are recommended.