Nitrogen and potassium interaction in oxisol soils under BRS 394 wheat cultivation

Abstract

Potassium and nitrogen are essential nutrients and their uptake and distribution within plants must be coordinated for optimum growth and development. We evaluated the interaction between nitrogen and potassium fertilization on the development of BRS 394 wheat, and the nitrate and ammonium levels in Oxisol soils. A 5² factorial design was used in a greenhouse experiment, with four replicates in randomized blocks, corresponding to five doses of nitrogen (0, 70, 140, 210, and 280 mg dm^-3) and five doses of potassium (0, 50, 100, 150, and 200 mg dm^-3). The variables analyzed were shoot dry mass; chlorophyll index; nitrate reductase; nitrogen, potassium, and protein concentrations in the leaves; and nitrate and ammonium levels in the soil. There was an interaction between nitrogen and potassium doses on the chlorophyll index, with nitrogen doses between 152.67 and 163.53 mg dm^-3 and potassium of 191.50 mg dm^-3 providing the highest chlorophyll index. The other variables were influenced separately by the nitrogen dose. The highest nitrate reductase enzyme activity was 1.30 µmol NO h^-1 g^-1 Fresh Matter, which was reached at a nitrogen dose of 95 mg dm^-3. Shoot dry mass, concentrations of nitrogen and total protein in the leaves, and concentrations of nitrate and ammonium in the soil were adjusted to the linear regression model as a function of nitrogen fertilization. The dose of nitrogen that promoted the best development of BRS 394 wheat and the highest concentrations of nitrate and ammonium in Oxysol soils was 280 mg dm^-3.