The research was driven by concerns over the skewed application of nitrogenous fertilizers and the threat to potassium (K) mining and the sustainability of the rice-wheat cropping system in the Indo-Gangetic plains. The objective was to identify potential K extractants as affected by different crop establishment methods and optimum nutrient levels. A split-plot experimental setup was established in 2012 with four levels of crop establishment methods and three nutrient management levels. Soil potential K extractants and critical concentration using Cate and Nelson was evaluated with twelve extractants: distilled water, 0.01 M calcium chloride (CaCl 2 ), 0.1 M barium chloride (BaCl 2 ), 1 N ammonium acetate (NH 4 OAc), 0.03 M sodium tetraphenyl boron (NaTPB), ammonium bicarbonate- diethylenetriamine tetraacetic acid (AB-DTPA), Mehlich I, Mehlich III, 0.002 M strontium chloride (SrCl 2 ), 0.02 M SrCl 2 + 0.05 M Citric acid and finally 1 N boiling nitric (HNO 3 ) acid. 1 M NaOAc showed a strong correlation with 0.03 M NaTPB ( r = 0.979 ** ), relative yield ( r = 0.927 ** to 0.984 ** ), plant K-uptake ( r = 0.930 ** to 0.974 ** ) and soil indices ( r = 0.913 ** to 0.97 ** ). Whereas, 0.002 M SrCl 2 was poorly correlated ( r = 0.231 NS to 0.641 * ) with soil and plant indices and had a lower soil K critical concentration (24 mg kg − 1 ). Unlike commonly used 1 N NH 4 OAc, 1 M NaOAc, and multinutrient extractants (AB-DTPA, Mehlich I, and Mehlich III) are better indices of relative yield and plant available K. Treatments with residue retention in both seasons and optimum K fertilization (60 kg K 2 O ha − 1 ) outperformed others in terms of crop yield and plant available K.
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Deepak et al. (2026) studied this question.