Characteristics of Phosphorus Adsorption of Acidic, Calcareous, and Plastic Film House Soils

Abstract

Continuous excessive application of phosphorus (P) fertilizer and manure in plastic film house soils can lead to an accumulation of P in soils. The understanding of P sorption by soils is important for fertilizer management. In this study, 9 samples were collected for acidic and calcareous soils as non-cultivated soil and plastic film house soils as cultivated soil Phosphorus sorption data of acidic soils fit the Langmuir equations, Freundlich equations in calcareous and plastic film house soils. In calcareous and plastic film house soils, the slope of isotherm adsorption changed abruptly, which could be caused P precipitation with <TEX>$CaCO_3$</TEX>. The calculated Langmuir adsorption maximum (<TEX>$S_{max}$</TEX>) varied from 217 to 1,250, 139 to 1,429, and <TEX>$714mg\;kg^{-1}$</TEX> for acidic soils, calcareous soils, and plastic film house soils with low available phosphate concentration, respectively. From this result, maximum P adsorption by the Langmuir equation could be regarded as threshold of P concentration to induce the phosphate precipitation in soil. Phosphate-sorption values estimated from one-point isotherm for acidic and calcareous soils as non-cultivated soils were comparable with the <TEX>$S_{max}$</TEX> values calculated from the Langmuir isotherm.