Absorption of macronutrients by soybean (Glycine max (L.) Merrill) as a function of fertilization with n, p and k

Abstract

This study was conducted with the objetives of determing the rate of macronutrient absorption considering the following items: . periods of greatest need for macronutrient nutrition; . amount of macronutrients accumulated in the different parts of the plant; . amount of macronutrients exported in seeds. A 3³ factorial experiment with three replications was used in this study. The experimental area was located at Piracicaba, SP, Brazil. The soil belongs to the Guamium series. IAC-2, an indeterminate soybean cultivar, was used. N, P and K were applied in the rows at the levels of 0, 20 and 40 kg/ha (N), 0, 60 and 120 kg/ha (p2o5), and 0, 30 and 60 kg/ha (k2o). Plant samples were taken at 21-day intervals starting at emergence and continuing until partial fall of the leaves (105 days after emergence). The several plants were analysed for macronutrients (N, P, K, Ca, Mg and S). At maturity, seeds from each plant were harvested and analysed for macronutrients. The following conclusions were drawn: . The period of highest rate of absorption of the nutrients by leaves and stems occurred between 44 and 55 days of age for the leaves, and between 55 and 76 days for stems. The amounts of nutrients removed, with exception of N and Mg, were affected by the levels of phosphorus applied to the soil; with exception of N and Mg, the nutrient contents varied according to plant parts; . The accumulation of N, P, K and Mg in the soybean seeds was influenced only by the levels of phosphorus applied to the soil. The accumulation of Ca and S in the seeds was not affected by the levels of N, P, and K. The removal of nutrients through harvest was influenced only by the effects of the treatments on yield of seeds.