RESPONSE OF ALFALFA HAY YIELD TO PHOSPHORUS FERTILIZATION IN 2 SOILS IN CENTRAL ALBERTA

Many soils in Alberta contain insufficient amount of available P and fertilizer P is needed for optimum crop yields. Fields experiments were conducted at two sites (Lacombe - Black Chernozem silt loam and Botha - Thin Black Chernozem loam) in central Alberta to determine the hay yield response of alfalfa (Medicago sativa leyss. cv. Rambler) to P fertilizer applied annually (0, 10, 20, 30, 40, and 60 kg P ha-1) or once initially (60, 120, and 180 kg P ha-1). In the initial application triple superphosphate was incorporated into soil prior to sowing of alfalfa in 1974 and in the annual application the P fertilizer was spread on soil surface for three years at Lacombe and for five years at Botha beginning in the spring of 1975. The hay yield increased with P application, but its magnitude of response to added P was lower at Botha than at Lacombe. The residual effect of large single P applications on hay yield lasted at least for five years.