Potassium Release in an Aeric Haplaquept as Influenced by Long-Term Rice–Rice Cropping with Different Rates of Fertilizers and Manuring

Abstract

Different fractions of potassium (K) and the kinetics of K release as influenced by 21 cycles of rice–rice cropping with different rates of fertilizers and manuring were investigated on an Aeric Haplaquept (kaolinitic Inceptisol) soil profile from Bhubaneswar, India. The neutral 1 N ammonium acetate–extractable K in the surface soil layer (0–15 cm) increased from its initial value of 11.2 mg K kg⁻¹ to 14.8, 14.2, and 17.5 mg K kg⁻¹ soil in different treatments. However, the nonexchangeable K content in the surface soil layer dropped considerably to a level of 4.8–20.0 mg K kg⁻¹ soil. Cumulative nonexchangeable K release after 121 h of extraction with 0.01 M calcium chloride (CaCl₂) was <14 mg K kg⁻¹. The first-order kinetic model best described the nonexchangeable K release. The decrease in pH and increase in iron (Fe) content indicated the possibilities of K supply to plants through the dissolution of soil minerals.

Keywords:

• Calcium chloride
• citric acid
• coarse texture
• kaolinite
• potassium dynamics