YIELD AND COMPOSITION OF ALFALFA AND CRESTED WHEATGRASS, GROWN SINGLY AND IN MIXTURE, AS AFFECTED BY N AND P FERTILIZERS

Abstract

The effects of four rates of N and P fertilizers applied in the spring to alfalfa and crested wheatgrass, grown singly and in mixture, at three ages of stand were investigated. N fertilizer increased yields and protein content of the grass in the year of application regardless of age of stand; the effect in subsequent years depended upon the level of yield in the year of application. The results indicated that grass should be fertilized with N every year at a rate related to the amounts of N removed from the soil in the preceding year. N fertilizer also increased the yield of the mixture in the year of application. The proportion of alfalfa in the hay mixture decreased with age and with applications of N fertilizer. This effect of N fertilizer was brought about by changes in the absolute yield of the grass component but not that of the alfalfa component of the mixture. The management of the mixture is affected by management of the grass component and any increases in yield and quality of the grass are at the expense of the alfalfa. P fertilizer slightly increased the P content of all forages, regardless of age of stand, both in the year of application and in the succeeding years, but did not increase yields.