Abstract
The P-fixing capacity of a soil governs the P-nutrition of crop plants. P-nutrition of the crop plant is more a soil problem and a higher dose of phosphatic fertilizer is necessary for soils having high P-fixing capacity. The phenomenon of P-fixation and the great variation in the P-fixing capacity of different soils has thus important bearing on crop response to P-application. The eastern plateau region of India with acid lateritic soil is chronically deficient in available phosphorus resulting in very low productivity. An experiment was thus carried out to estimate the P-fixing capacity of soil collected from two depths, 0 - 20 cm and 20 - 50 cm, from the Agricultural experimental farm of Indian Statistical Institute, situated at Giridih, Jharkhand, in the eastern India. The soil was acidic in reaction (pH-5.4) with presence of Fe (1.60%) and Al (17.2%). The P-fixing capacity of the soil was estimated to be 59.60% and 64.94% for the surface and the subsurface soil respectively showing lower P-fixing capacity of the surface soil as compared to the subsurface soil which may be due to presence of more organic matter in the surface soil as organic molecules released on decomposition of organic matter complexes with Fe and Al in the soil thereby blocking the P-fixing sites in the soil.
Highlights
Phosphorus (P) is an essential element for plant growth and productivity, and lack of available P in soils can severely affect crop yields [1]
The P-fixing capacity of a soil can be drawn from the relationship of added phosphorus and extracted available phosphorus on addition of graded quantum of phosphorus, after a time interval, in a particular soil
The data on addition of graded amount of inorganic phosphorus (Table 2) at both the soil depth indicated that the relationship between available and added phosphorus was virtually linear (Figure 1)
Summary
Phosphorus (P) is an essential element for plant growth and productivity, and lack of available P in soils can severely affect crop yields [1]. Plants extract P from the soil solution in the form of orthophosphate ion ( H2PO 4 or HPO4 ) and there is strong competition between plants and soil minerals for these forms of P, in the highly weathered soils of the tropics, most of which contain large amounts of iron oxides, aluminum oxides, or amorphous alumino-silicate clays. These soil minerals “fix” P firmly through a process known as sorption, making the P virtually unavailable for plant uptake [2].
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