Abstract
Single application of fertilyzer in spring on orchard grass (Dactylis glomerata L. cv. KITAMIDORI) cultivation was studied using controlled release polyolefin coated urea (POCU) to conduct labour saving and to maintain stable plant density. Field experiment was carried out on Kawatabi Andosol in 1988 to 1989. The following three treatments were designed. Conventional plot: 4 times application of N fertilyzer (10-8-4-2 gN/m^2), coated urea plot: single application of N fertilyzer (20gN/m^2 of POCU, LP100 and 4 gN/m^2 of urea and-N plot : none application of N fertilyzer. 1) A relationship between days calculated as 25℃ after application (X) and cumulative percentage of nitrogen release from POCU,LP100 (Y) was expressed by the following equation. Y=0.759X+4.67(r=0.988^<***>, n=9) There was a quite high correlation between these two factors. However, the release rate of nitrogen from LP100 applied at the surface of grass land was about 30% faster than that applied in plow layer. 2) The relative dry matter yields of orchard grass of conventional plot, coated urea plot and -N plot were 100, 110-111, and 55-83, respectively. They were closely related to both leaf color index and amounts of nitrogen absorption. 3) The recoveries of N fertilyzer of plant both in conventional and coated urea plots were calculated by substructing the amounts of nitrogen uptake in -N plot. These recoveries were 53% and 68%, respectively. Therefore, recovery of coated urea by plant seemed to be much higher than that of urea. 4) We may conclude that single application of nitrogen fertilyzer in spring using POCU is one of the most feasible methods judging the matter from the viewpoints of the labour saving, high yielding, envirmental conservation, etc.
