Uptake of Fertilizer Nitrogen by Pasture Plants

Abstract

Orchard grass and Ladino clover were grown in pure and mixed stands using resin cylinders which were filled with Iwate volcanic ash soil and placed in field. ^<15>N-labelled nitrogen in form of ammonium sulfate was applied to them at the three levels equivalent to 10, 20 and 50kg N/10a per year. The results of this experiment were summarized as follows: The same amount of fertilizer nitrogen was recovered both in grass-clover mixture and pure grass stand. In grass-clover mixture, the uptake of fertilizer nitrogen by grass was not affected so much with clover accompanied, but the presence of grass reduced the uptake of fertilizer nitrogen by clover. The nitrogen recoveries by grass-clover mixture were 36% for basal and 70, 50 and 50% for top dressing in spring, summer and fall respectively. With increasing nitrogen application, grass became dominant. The nitrogen recoveries by plants for the application of 10, 20 and 50kg N/10a were 47, 51 and 52% respectively.