Distribution and Variation of Potassium in Black Soil at Different Stages of Crop Growth in Maize (Zea mays)

Potassium (K) is the third most important major plant nutrient with numerous functions. The availability of K depends on concentration relative to that of Ca2+ and Mg2+ than on the total quantity of K present. The level of extraction of K by different extractants followed the order: boiling HNO3 (1 M) > Non- exchangeable K > Exchangeable K > Water soluble K. The amount of K extracted by different extractants was more in non- calcareous soil followed by calcareous soil. To know the K availability in both the soils, a pot culture experiment was conducted with the two soils (i.e., calcareous and non-calcareous) to know the response of maize to K application. Results showed that a significant higher value of available K in calcareous soil under potassium @ 120 kg K2O ha-1 treatment followed by 80 kg K2O ha-1 in non-calcareous soil irrespective of critical growth stages of hybrid maize. Among the K fractions, water soluble K was the least in magnitude and lattice K was found to be dominant one. Application of 120 kg K2O ha-1 recorded the highest potassium in all the K fractions (water soluble K, exchangeable K and nitric acid soluble K) in all stages of crop growth in calcareous soil whereas in non-calcareous soil 80 kg K2O ha-1 recorded high in all the fractions and the results emphasizing the importance of potassium in soil. Grain and straw yield of hybrid maize were significantly higher under 120 kg K2O ha-1in calcareous soil and 80 kg K2O ha-1 in non- calcareous soil which is well evidenced by a yield increase of 37.7 % over control. A significant and positive correlation was existing between all fractions of potassium viz., HNO3 soluble K, non- exchangeable K, exchangeable K, water soluble K and available K with grain and stover yield in calcareous soil and non- calcareous soil. It was found that calcareous soil showed comparatively better response to the application of potassium especially in water soluble K with an R2 value of 0.917** followed by HNO3 soluble K with a R2 value of 0.895**. Therefore, the present investigation stresses the vital importance of inclusion of higher dose of potassium in calcareous soil for maintaining soil K dynamics and enhancing yield of hybrid maize so as to sustain soil productivity.