Releasing Patterns of Potassium and its Relationship with Different Forms of Potassium in Acid Alfisols Soils of Ranchi, Jharkhand, India

Abstract

A study was conducted during 2017-2018 at the Experimental Farm of Birsa Agricultural University, Kanke, Ranchi, Jharkhand, India to assess the releasing patterns of potassium and its relationship with different forms of potassium in surface (0-15 cm) and sub-surface (16-30 cm) soils of acid alfisols from the selected 9 treatments under long-term nutrient management practices in maize-wheat cropping system. The releasing power of soil potassium is an index of the availability of the nutrient to the crops over a longer duration and in general, it indicates the sum of water-soluble K, exchangeable K, and a fraction of non-exchangeable K which is not immediately available to the growing plants, but will be slowly available over a longer period. Repeated extraction with boiling 1N HNO3 has been suggested as one of the methods to assess the potassium-releasing capacity of soils. In this context, cumulative K, constant rate K, and step K as a part of non-exchangeable potassium proposed by Haylock (1956) measure the potassium-releasing capacity of soils more effectively under intensive crop cultivation. The amount of K release in successive extraction with boiling 1N HNO3 decreased consistently and reached a plateau at the 8th and 9th extraction steps in both depths of soils. Cumulative K is highest in INM (T6) while constant rate K and step K are highest in Lime, FYM, P2O5, and K2O treated plots (T8). The lowest contribution of potassium release patterns is generally observed in the control plot (T1). Also, the K release was found to be maximum in surface soils than in sub-surface soils concerning various selected treatments. Cumulative K, Constant- rate K, and Step K had highly significant and positive correlations with different forms of potassium (Water soluble K, Exchangeable K, Non-Exchangeable K, Total K, and Lattice K) in both depths. The potassium-releasing patterns evaluated through cumulative K, constant rate K, and step K could be meaningful for making fertilizer recommendation programmes, especially in intensively cultivated areas. Hence, the importance of study in terms of the possible contribution to plant available pool of soil K through potassium release patterns in two depths of given soil has been pointed out.