Abstract
In this experiment, the relation between basal coverage and the yield were studied on orchardgrass swards in 1970. Swards were treated with 3 levels of fertilizer application (N.P.K. 1kg/a/year, 2kg/a/year and 4kg/a/year). Each sward were divided into 4 plots which treated with different degrees of basal coverage in early spring of the year, namely 25, 35, 50, 65% of basal coverage in plots of 4kg/a fertilization and 35, 50, 65, 75% of basal coverage in plots of 1kg and 2kg/a fertilization. The results were summarized as follows ; 1) In the sward of low level of fertilizer application, orchardgrass swards continued as same degrees of basal coverage as treated in early spring through the year even though in the plot of high basal coverage. But in the plots of heavy fertilizer application, it was difficult to keep up the high basal coverage and decreased gradually with the cutting were repeated (Fig.1). 2) In the plots of low level of fertilizer application, linear correlation were obtained between basal coverage and fresh yields in each cutting, high yield were obtained in plots of high basal coverage. But in the swards of heavy fertilizer application, the maximum yield was not always obtained with high basal coverage but with middle degree of basal coverage, namely there was the optimum basal coverage for maximum yield (Fig.3). 3) The optimum basal coverage for maximum yield was 35-46% in the sward of 4kg/a fertilization, and 45-56% for 2kg/a fertilization. The optimum coverage was seemed to decrease according with the increase of fertilizer application level. 4) The reason and the mechanism of these results as above mentioned were discussed with the relation between basal coverage and number of stubbles in unit area, basal coverage-stubble size relation and the relation between yield and number of stubbles (Fig.5 and 6).
