Variation of pH, specific conductance and N, P, K, Ca and Mg solubility in four flooded soils

Abstract

The work discussed in this paper deals with the effects of waterlogging on soil pH, specific conductance and on the concentrations of N, P, K, Ca and Mg in the percolates of four rice soils of Rio Grande do Sul. After flooding, the soil pH increased and the increase was greater in the unfertilized soils than that of the fertilized soils. Flooding increased the specific conductance of the soil percolate by promoting the displacement of the nitrogen, phosphorus, potassium, calcium and magnesium from the soil exchange complex to the soil solution. Almost all nitrogen applied to the soils was lost at the beginning of the experiment. The loss of nitrogen was caused by nitrification and denitrification processes that occur in paddy soils. The phosphorus applied to the soils as fertilizer was fixed at the beginning of the flooding. The fixation on the phosphorus was greater in the Pelotas and Vacacaí soils than that observed in the Formiga and Formiga-Banhado soils. Only after reduction of the soil was the solubility of phosphorus increased.