Effect of Pistachio Seedlings Planting on Chemical Forms of Potassium in Some Calcareous Soils of Rafsanjan

Proper plant nutrition is one of the most important factors in improvement of crop quality and quantity. Potassium is one of the essential macronutrients for plant growth. Understanding the different forms of potassium is important in evaluation the situation of this element in soil fertility and plant nutrition. Incorrect understanding of the potassium dynamics in soil off leads to improper management of soil fertility. Soil potassium exists in four forms: soluble, exchangeable, non-exchangeable and structural that their availability for plant are different. Soluble and exchangeable forms are widely used for determination of the potassium availability for plants. In addition to the exchangeable potassium, non-exchangeable potassium plays an important role in plant nutrition. This study was done to evaluate the different chemical forms of potassium and effect of pistachio seedlings planting on changes of their forms in some calcareous soils of Rafsanjan. For determination of the chemical forms of their forms potassium in 20 calcareous soils samples of Rafsanjan before and after planting, 1 M NH4OAc, boiling 1 M HNO3 anddistilled water were sample used. Results indicated that there was no significant difference between the soluble potassium before and after the planting. However, amount of exchangeable potassium increased from 239 mg kg-1 soilbefore planting to 270 mg kg-1 soilafter planting and non-exchangeable potassium decreased from 683 mg kg-1 soilbefore planting to 570 mg kg-1 soilafter planting. Multiple regression equations indicated that the different forms of potassium in soils were correlated with the physical and chemical properties of the soil such as clay content.