Comparing distinct soil test methods for available nitrogen, phosphorus and potassium for groundnut (Arachis hypogaea L.) and wheat (Triticum aestivum L.) grown in North Western India

Abstract

An experiment was conducted during 2020-21 and 2021-22 in the tarai region of Uttarakhand in order to find simple, economical, effective, and plant uptake correlated soil test methods for determining the available nitrogen, phosphorous, and potassium. Before sowing of groundnut and wheat, soil samples were collected to evaluate available nitrogen, phosphorus, and potassium soil test methods. Wet oxidation was used for organic carbon, alkaline potassium permanganate (KMnO4) was used for mineralizable nitrogen, Olsen's-P, ammonium bicarbonate-diethylene triamine penta acetic acid (AB-DTPA), Mehlich-1 and Morgan-P were used to extract phosphorus (P), and ammonium acetate (NH4OAc), ammonium bicarbonate-diethylene triamine penta acetic acid (AB-DTPA), Mehlich-1 and Morgan-K were used to extract potassium (K). The suitability of these methods for various soil nutrients was assessed by comparing R2 values (coefficients of determination) derived through regression analysis. The results showed that the R2 values of the derived equations by using different combinations of soil test methods to determine available N, P, and K in soil were highly significant in both crops. Superior R2 value for groundnut (0.853**) was observed with the combination of alkaline KMnO4, Olsen’s P, Mehlich-K and for wheat (0.515**) the combination of alkaline KMnO4, Mehlich-P, NH4OAc–K. It found that these combinations are more superior to other methods and more promising.