Evidence of nitrogen and potassium losses in soil columns cultivated with maize under salt stress

Evidências de perdas de nitrogênio e potássio em colunas de solo cultivadas com milho sob estresse salino

ABSTRACT

The aim of this study was to evaluate the accumulation of salts in the soil from irrigation water and of N and K from fertilization. The experiment was conducted in PVC columns (20 cm in diameter and 100 cm in height), filled with non-saline soil, and cultivated with maize. A completely randomized block design in a 4 x 4 factorial was used, with four levels of salinity (0.5, 2.5, 5.0 and 7.5 dS m^-1), four N rates, and five replicates. Nitrogen was applied as urea and potassium nitrate at the following rates: N1: N recommendation for maize (2.6 g column^-1); N2: 0.3 times (0.78 g column^-1) the recommended N1 dose; N3 and N4 with N based on N1 and N2 doses, respectively, reduced proportionally based on the evapotranspiration reduction caused by salinity. After 74 days from sowing, root and soil samples were collected at different soil depths. The electrical conductivity of the saturated extract (ECe) and the concentration of ions (Ca²⁺, Na⁺, and Cl^-) increased as a function of salinity and soil depth. The opposite was observed for the root system. The increase in salinity also resulted in K⁺ and NO₃^- accumulation in the soil column, mainly in treatments with higher N rates (N1 and N3). At the end of the experiment, 88% of the NO₃^- applied at the highest salinity treatment (7.5 dS m^-1) and the highest N rate (N1) was below 20 cm soil depth, evidencing a N loss process caused by leaching.

Key words:
salinity; nitrate; nutrients leaching