The effects of ammonium and nitrate nitrogen on the growth of perennial rye grass

The results show clearly a more rapid and greater uptake of ammonium than of nitrate nitrogen by perennial rye grass grown in a sand-bentonite medium ofpH 7·61. The extent to which the extra uptake with added ammonia was reflected in increased yields was dependent upon the age of the grass. Except in the very early stages the percentage nitrogen content of the herbage was higher where nitrate nitrogen was applied than where ammonium nitrogen was applied. This indicates that any nitrate absorbed by the plant was less, efficient in increasing yields than was ammonium nitrogen. The percentage P205content of the grass was higher where the nitrogen was applied in the ammoniacal form than where it was applied as nitrate, and it appears that this greater P205uptake with ammonium nitrogen resulted in increased growth.