Phosphorus and potassium fertilization of dry pea
In Quebec, the P recommendationsfor dry peas( Pisum sativum L.) are nearly three times higher than those in western Canada, while recommendationsfor K are at least 20% lower. The objective of this project was to re-evaluate the P and K needsof dry peas under the climatic conditions of the Saguenay-Lac-Saint-Jean region (Quebec, Canada) in soils with a range of soil P and K availabilities. The treatments consisted of four P rates (0, 20, 40, 80 and 160 kg P 2O5 ha-1) and three K rates(0, 50 and 150 kg K2O ha-1). The trials were conducted at two sites over 3 yr. Site 1 was classified as low in P availability and site 2 as medium according to the soil analysis. Both sites had a medium level of soil K availability. Grain yields increased significantly, by 6%, with increasing fertilizer P (3246 to 3437 kg ha-1). Potassium fertilization had no significant effect on grain yields. Grain yields were also 37% higher in the highest soil P site. This low response of the crop to mineral fertilizers was attributed to the significant soil contribution to crop P and K needs. Soil tests have also indicated an enrichment of P and K with large inputs of mineral fertilizers. Thus, a rate of 30-35 kg P2O5 ha-1 for P poor soils would be sufficient to meet the crop needs. For soils with moderate levels of K (201-400 kg K ha-1), a rate of 50 kg K2O ha -1 would be sufficient to meet the crop needs and to maintain the soil fertility.
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