Assessment of fertilizer P residues in a calcareous vertisol

Abstract

The amounts of available P in a Typic Pellustert containing different levels of residual fertilizer P were assessed in a field experiment and chemically with cation-anion-exchange resin, using: (i) P desorbed after 1 extraction, (ii) cumulative P from 8 extractions [Resin8-P] and (iii) the asymptote of the extraction curve. P exchangeable to 32p, Olsen-P and P extracted by dilute salt solution (0.03 M KC1) were also measured. P available to sorghum in 1989 was strongly influenced by fertilizer P applied in 1988, but not by P applied in 1987. Olsen-P and Resin8-P both reflected well the effects of residual P on yield and P uptake and could therefore be used to predict available residual P. The amounts of Resin8-P were much larger than Olsen-P, so it was easier to observe the differences between soil treatments, but Olsen-P gave the better correlations with grain yield and P uptake.Multiple regressions of crop yield or P uptake with amounts of P applied in 1987 and 1988 gave the best correlations, without the need for practical work. Thus, the development of an appropriate model based on records of P fertilization is seen as the most effective way to predict availability of residual P. Assessments related to the P intensity and desorption rate using resin were not able to improve predictions of available P, indicating that within one soil the quantity of residual P is most important, but for comparisons between soils, account will need to be taken of differences in soil characteristics.

Vertisols of tropical Indian environments: Pedology and edaphology

“…Therefore, the highest surface area of smectite and/or hydroxides of iron and aluminium with no positive sites plays a small role in the adsorption of added negatively charged phosphate ions in vertisols. This supports the ICRISAT's classical experimental observations on P adsorption and desorption on vertisols (Kasireddipalli soils), which clearly indicate that P adsorption is not a major problem in the vertisols and that all the adsorbed P is easily exchangeable by P 32 and a small amount of P is adsorbed in the non-exchangeable form (Sahrawat and Warren, 1989;Shailaja and Sahrawat, 1994;Warren and Sahrawat, 1993). ICRISAT (1988) envisaged that CaCO 3 could adsorb P because the effective sorption by CaCO 3 is not well understood, and P adsorption is not always related to CaCO 3 content (Goswami and Sahrawat, 1982); perhaps the critical factor here is the quality of the CaCO 3 .…”

Effect of Mixing Soil Aggregates on the Phosphorus Concentration in Surface Waters

“…Among the soils from Great Britain, resin P, which is one measure of plant‐available P (Somasiri and Edwards, 1992), was always greater in the fertilized (G3, G6, and G9) than the unfertilized (G2, G5, and G8) soils. Previous research has shown that long‐term fertilization increases plant‐available P in soils, as measured by extraction with ion exchange resins (Warren and Sahrawat, 1993). Water‐soluble P ranged from 0.1 mg kg −1 in G2 to 20.8 in D3 mg kg −1 Differences in the sorption properties between soils are clearly evident; for example, the G soils contained little WSP relative to the other soils and relative to their resin‐extractable P contents.…”

Assessment of the effect of time and temperature on the availability of residual phosphate in a glasshouse study of four soils using the Olsen method

“…The soil samples collected before sowing the ryegrass and after the ®nal harvest were analysed for isotopically exchangeable P (P e ) by the method of Warren & Sahrawat (1993).…”