Abstract
The purpose of this study is to clarify suitable cutting stages for the 2nd and 3rd crops of perennial ryegrass swards under 3 levels of fertilization. Each growth was measured weekly upto 8 weeks after cutting, and the changes of measured values with time were significantly fitted by cubic regression equations. Maximum stages of average productivity (green yield/days after cutting) and maximum stages of green yield were calculated using cubic regression equations. It was concluded that under high fertilization, the suitable cutting stages should be around the maximum stage of average productivity, 5.5 and 4.8 weeks after cutting for the 2nd and 3rd crops respectively, in order to keep high growth-rates and less accumulation of dead material through the growing season. And under low and medium fertilization, the suitable cutting stages should be around the maximum stage of green yield, 6.8, 7.0 weeks for low and 6.8, 6.7 weeks for medium after cutting in the 2nd and 3rd crops respectively, in order to keep high efficiencies of nitrogen fertilizer for dry matter production.
