Response of field peas to phosphate fertilization

Abstract

Canadian Prairie Provinces in general, and Saskatchewan in particular are major producers of peas worldwide. Individual provincial criteria for P application are considerably different from each other. Further introduction of new pea varieties and the adoption of direct seeding practices prompted us to re-evaluate these criteria. To this end, two experiments with field peas (Pisum sativum L. var. Carneval) were carried out between 1994 and 1998 at nine different locations in Alberta. The first experiment was carried out in 1994 and consisted of three trials with six rates of P (0, 4.4, 8.7, 13, 17.5 and 21.8 kg P ha-1) in the form of monoammonium phosphate (MAP) (12-51-0). To eliminate the impact of varying N rates along with P, a series of 21 trials and a uniform design that included five rates of P (0, 6.5, 13, 19.5 and 26 kg ha-1) in the form of triple super phosphate (0-45-0) and two methods of placement (seed placement or side banding) were subsequently carried out. There was a significant response to P application at all 13 sites of both experiments that contained 10 or less mg of a Modified Kelowna (MK) extractable-P kg-1 of soil. Side banding resulted in significantly higher yield in only three trials. Maximum average yield increase of 645 kg seed ha-1 was obtained with application of 19.5 kg P ha-1; it was influenced by soil texture as the magnitude of response was greater on loamy (535 kg seed ha-1) than on clay loam soils (285 kg seed ha-1). There was no significant yield increase in the trials that contained greater than 10 mg MK-P kg-1 soil. Reduction in plant population was more frequent as a result of seed placement (nine cases with P < 0.1) than side banding in both experiments. The impact of P fertilization on seed moisture was not consistent. The ability to side band or to seed with an increased seed bed utilization may fulfil the need for application of greater rates of P than the ones currently recommended for prairie soils. Key words: Seed placement, side banding, triple super phosphate, monoammonium phosphate