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Use of Phosphorus and Potassium Fertilizer in the Fall preceding the Bringing into Production of a New Blueberry Field

Abstract: A trial was established in 1999 to evaluate the effect of applying phosphorus and potassium in the fall preceding the bringing into production of a blueberry field versus applying these elements in the spring at the time the field is brought into production. The trial consisted in a control treatment (no fertilizer), a treatment with application of P and K in the fall followed by an application of N the next spring, and a spring treatment with a complete fertilizer (NPK). The treatments with fertilizer all received the equivalent of 50 kg/ha of N, P205, and K20. At tip dieback, soil and leaf analyses were done. The soil was analyzed by level, i.e., 0-5 cm, 5-10 cm, and 10-15 cm. These analyses made it possible to evaluate the movement of the elements in the soil and their content in the leaves. It was found that the movement of phosphorus was more rapid than anticipated and that there was no difference in the leaf P and K content between the treatments having received fertilizer. The availability of these elements with a spring application is therefore similar to that with a fall application. Consequently, fall application is not justified to improve the degree of P and K absorption by plants nor from the financial standpoint. This trial also enabled us to determine the level of the main elements in the various soil layers analyzed.