Dynamics of Soil Potassium Under Prominent Cropping Systems of Western Uttar Pradesh

Abstract

The study was conducted to assess different pools of potassium in soil and to study the kinetics, quantity-intensity relationships and fixation of potassium in soils under different cropping systems of Western U.P.. For this, soil samples were collected at three different depths (0-15, 15-30 and 30-45 cm) from each of the cropping system from various locations of Western U.P. Highest value of pH in soil was observed under barren system than rest of the cropping systems. Averaged over the depths, highest amount of water soluble K (WSK) was observed in rice-wheat system followed by sugarcane-ratoon-wheat, rice-potato, veg-veg, rice-mustard and least in barren system. Similar trends were followed for available K, non-exchangeable K (NEK), fixed K and total K, cumulative release of K and initial release rate (‘a’ value). Data on release kinetics were best fitted in power function followed by first order equation and simplified elovich equations with highest R2 values and lowest SEE values. It was observed that significantly positive correlation was there between WSK and NEK. The amount of NEK in soils was greatly affected by the clay content and the initial release rate (‘a’ value) was found to be significantly positively correlated with available K, NEK and cumulative release of soil K whereas the apparent release rate coefficient (‘b’ value) was found to significantly negatively correlated with available K, NEK and cumulative release of soil K. This might be due to the high amount of initial K release from the soils which had higher amount of available K and NEK but in due course of time as most of the K was released initially from those soils, the apparent release rate coefficient showed significantly negatively correlation. A positive and significant correlation was found between PBCK and non-exchangeable or slowly available K. This may be an indirect relationship since PBCK is linearly related to clay content, which in turn is the source of non exchangeable potassium. The K-fixation capacity had significantly positively correlations with clay content and CEC. Thus, it may be concluded that the rice-wheat soils in the present investigation might sustain itself for a considerable period of time even without K application, but other cropping systems would require frequent applications of adequate amounts of K-fertilizer for sustenance.