PRODUCTIVITY AND CHEMICAL COMPOSITION OF ALFALFA AS INFLUENCED BY VARYING LEVELS OF PHOSPHORUS AND POTASSIUM APPLICATIONS

Abstract

In a greenhouse study conducted at the Experimental Farm, Lennoxville, Quebec, P2O5 and K2O were applied separately at rates of 0, 60, 120, 180 and 240 pounds per acre and in all combinations to surface samples of two soil types prior to seeding alfalfa. Nine cuttings were taken and fertilizer treatments were re-applied every three cuttings.On Greensboro loam soil, an initial application of 180 pounds of P2O5 per acre at seeding time followed by applications of 120 pounds after the third and sixth cuttings were necessary for continued yields of alfalfa. On Coaticook silt loam soil, little was gained in yield increases from P2O5 applications higher than 60 pounds per acre. Both soils contained, at the beginning of the investigation, sufficient amounts of available potassium for the proper establishment and satisfactory growth of alfalfa. As cropping continued, the needs for applied potassium increased markedly. Yields increased with increasing levels of K2O; however, the response to potassium was more pronounced on Greensboro loam soil than on Coaticook silt loam soil.The Ca content in alfalfa was affected little by phosphorus fertilization but decreased with the potassium supply. The P content increased with increasing rates of phosphorus fertilizer and decreased with increasing rates of potassium fertilizer. The per cent K increased with increasing rates of potassium application and decreased with increasing rates of phosphorus application.