Effect of Liming on Quantity-Intensity Parameters of Phosphorus in Acid Soils of Karnataka

摘要

About 40% of cultivated area in Karnataka is base-unsaturated, affecting crop production to varying degrees (Ananthanarayana and Ravindra 1998). Soluble phosphates like monocalcium phosphate or fertilizers containing monocalcium phosphate upon addition to acid soils get slowly precipitated as iron phosphate and aluminium phosphate (Barber 1995). Liming is the most important practice followed in acid soils to counter acidity and increase phosphorus availability. Application of lime to acid soil can stimulate crop growth by eliminating toxicities of Al and Mn and increasing the availability of certain plant nutrients (Fageria and Baligar 2008). Liming has always given mixed response and it has been reported to increase (Ananthanarayana and Ravindra 1998), decrease (Haynes and Ludecke 1981) or not affect (Sumner 1979) the extractable soil phosphorus. In soil, phosphorus availability is controlled by the interplay of factors such as quantity, intensity and phosphate buffering capacity of soils. Soil solution is the key to plant nutrition because all phosphorus that is taken up by plants comes from phosphorus dissolved in soil solution. As the amount of phosphorus in soil solution is low, it must be replenished by as many as 50 times during a growing season to meet the nutritional needs of typical crop (Larsen 1967). Therefore, quantity factor is of significance in the replenishment of soil solution when its intensity is depleted by the removal of phosphorus by crops. Lime addition possibly brings about conversion of insoluble aluminium and iron compounds of P into more readily available calcium salts and sustains phosphate-buffering action in acid soils (Mahapatra 1969). With this backgroundinformation, the present investigation was undertaken to study the effect of lime application on quantity-intensity parameters of P, a measure of phosphorus supplying capacity, in some acid soils of Karnataka.