An experiment measuring effects of N, P and K fertilizers on yield and N, P and K contents of grazed grass

An experiment was started in 1959 to measure effects on grazed permanent grass of ammonium sulphate, calcium nitrate, superphosphate and muriate of potash; yields and N, P and K contents of the herbage were measured from 1961 to 1964. 2. Applying 1.5 cwt. N/acre per year (in four bi-monthly doses) consistently increased yields. The first and fourth cuttings yielded less with 3.0 cwt. N/acre per year (also in four bi-monthly doses) than with 1.5 cwt. N/acre, but the second and third cuttings yielded more; the total additional yield from 3.0 cwt. N was small. Yields were increased equally by ammonium sulphate (providing that lime was also applied) and calcium nitrate. 3. Yields were increased more by P than by K; the increase from P was greater when N was also applied.