Fertilizer Requirement of Irrigated Alfalfa

Surveys have indicated that there is a discrepancy between soil and tissue tests for P and K in many irrigated alfalfa fields in southern Alberta, and that insufficient P and K was being applied to these fields. Results of the last 3 years indicate that a combination of soil and tissue tests provide the best option for predicting P response in alfalfa. However, neither worked well for K. Alfalfa did not respond to K fertilization even when soil and tissue tests predicted it should and when the soils had a long history of alfalfa production without K fertilization. More research is needed to understand this peculiar lack of response. Despite the lack of response to applied K, this study has demonstrated improved yields from applied P and will undoubtedly encourage farmers to use more phosphate fertilizers. AB-11