Soil testing and estimation of economic rates of P and K fertilization for maize in Paraná State, Brazil

Abstract

From 1975 to 1978, a set of trials was carried out, in order to: a. Identify response classes of maize (Zea mays L.) to phosphorus and potassium in the soil analysis; b. Adjust production functions for each class and c. Estimate economic rates of fertilization based on these functions. Results allowed: 1. To verify greater response to phosphorus, compared to potassium, in increasing maize yields; 2. To establish limits for low (bellow 3,0 ppm). medium (3.1 to 7,0 ppm), high 7.1 to 16,0 ppm) and very high (above 16,0 ppm) for nutrient classes as a basis for interpretation of phosphorus availability by means of soil analysis (Mehlich's extractor); 3. To estimate economic dosis for phosphorus fertilization, by Mitscherlich's equation, for different ratio between fertilizer prices and maize prices, in soils with low and medium available P.