Botanical Structure of Sown Grassland : II. Growth of the individual plant in the population of orchardgrass sward

Abstract

In order to clarify the process of decrease of density in sown grassland, two clones of orchardgrass namely semi-erect form and prostrate form were prepared to make the population in the fall of 1970. Several individuals of a clone were planted at spacing of 20×20cm. in a plot size of which was 1.2m×1.2m. Each clone was treated with two, levels of fertilizer applications. Cutting frequency was four times in a year, 1st June 7 (full heading time), 2nd July 16, 3rd Aug. 25, 4th Nov. 8, and height of cutting was 10cm above the soil surface. The trend of individual plant growth, the correlations between before and after cutting on several characters and the influence of adjacent plants upon the growth of an individuals were evaluated. The results are summarized as follows ; 1) In heavy fertilized plots the coefficients of variation of plants weight and number of tillers per plant in the population were increased during four times of cutting (Table 1). 2) A high correlation was found between and after cutting on the plant weight and number of tillers per plant, suggesting that in general the plant which have large number of tillers and weight have a tendency to regrow with large number of tillers and weight after cutting (Table 2). However, there were changes of order in individual weight through. the four cuttings, especially in individuals having about average plant weight of a population. In individuals of the greatest and the smallest plant weight, the order little changed. during the season (Fig.1). 3) Changes of order of plant weight seemed to be influenced by the adjacent individuals. It was shown that if an individual have a greater weight and number of tillers than the adjacent plants, it will grow more vigorously than the adjacents and if it is smaller than the adjacent plants its growth will be inferior to the adjacents (Fig.2).