Effects of Moisture Regimes and Calcium and Sodium on the Depth Distribution of Potassium in the Gypsum Soil

Potassium is one of the macro nutrients, which plays a major role in the growth and development of plants. One of the factors affecting the amount of soluble and exchangeable potassium is the leaching. Study the movement of potassium in agricultural soils and reduce leaching of recommended fertilizer to subsurface soil and out of the root zone is essential. The aim of this study was to evaluate the depth distribution and potassium exchange by salts of calcium and sodium in different water regimes.
Effects of calcium and sodium salts on the depth distribution of soluble and exchangeable potassium in a calcareous soil were studied under the influence of different moisture regimes. The experimental design was a factorial with three replications. Treatments were four levels of salt (calcium chloride, calcium sulfate and sodium chloride, each 10 meq per kg of soil and one without salt or control), three levels of the moisture regimen of soil (50%, 75% and 100% of the water holding capacity in the soil), and three depths of soil columns (5, 10 and 20 cm). The concentrations of soluble and exchangeable potassium were measured in the treated soils.
The results showed that the concentration of exchangeable and soluble potassium in the soil profile depends on the moisture regime's treatment. The maximum and minimum of the soluble or exchangeable potassium of soil was found in the moisture regime of 50% and 100%, respectively, and these value increased with increasing soil depth. The ratio of exchangeable potassium to soluble was increased with increasing the soil moisture. The salts of calcium chloride> sodium chloride> calcium sulfate, respectively, had most effects in the soluble and exchangeable potassium soil and also increased their ratio in the soil profile. The higher levels of the soil water increased the movement of potassium in the soil profile. Probably, the ionic strength and charge of cations of solution salts applied increase the concentrations of soluble and exchangeable potassium in the soil. The calcium ions cause soil particles to be collected and the result is an increase in soil permeability. It is another reason that more immigration potassium ions in the presence of calcium.
High leaching, especially in saline soils not only the leaching of potassium and out of reach of the element for plants but also pollute groundwater resources and this would be considered a serious threat to the environment. In the end, it can be stated that the correct planning and management of resources for the proper use of potassium fertilizers, accuracy and attention to quality irrigation water consumption affect potassium leaching loss.