Identification of Phosphate Sorption-Desorption and Accumulation Characteristics to Reduce Environmental Consequences

Phosphorus (P) enrichment of soil due to the intensification of P fertilizer usage in crop production has resulted in eutrophication and serious economic consequences. Further, rapidly decreasing P reserves have renewed interest in improving more sustainable soil P management through monitoring diverse soil P reactions in contrasting soils. Therefore, the study was conducted to (i) characterize P sorption and desorption capacities related to soil properties and (ii) determine the added P availability and distribution among the different pools of P over the period concerning P sorption capacity of the soils. Three soils, namely Ultisols, Entisols, and Inceptisols, were equilibrated with a series of P concentrations to study P sorption-desorption using Langmuir isotherms. These soils were subjected to a sequential extraction procedure to study fractions in different pools after incubating with added P for 120 days. Maximum P sorption for Ultisols, Entisols, and Inceptisols were 1,428.6, 1,666.7, and 3,333.3 mg kg(-1) soil, respectively. Phosphorus desorption by Ultisol was about 1.7- and 4.2-fold higher than Entisols and Inceptisols. The maximum P sorption showed a negative and significant correlation with soil pH (r = -0.88), whereas P des % has a significant and positive correlation (r = 0.98). Exchangeable Al, Al-ox, Al-cD, and Fe-ox showed a significant positive correlation with maximum P sorption and a negative correlation with P des %. During incubation, 93.3% of added P became non-extractable in Inceptisols, and in contrast only 64.3% for Ultisols. A greater increase in labile NaHCO3-P fraction was found in Ultisols from 66.96 to 135.6 mg/kg at the end of the incubation. Accordingly, the soils with lower sorption capacity consist of more labile P pools, which indicates a higher risk of the loss of P from the soil.