The effect of soil texture on the dissolution of North Carolina phosphate rock

Abstract

Laboratory investigations of the dissolution of North Carolina phosphate rock (PR) in soil, as affected by soil texture, were conducted using soils created by mixing various proportions of the < 45 pm and > 45 pm fractions of a lateritic soil. The dissolution of PR in soil, and the resulting changes in plant available P, were estimated by measuring increases in exchangeable Ca (ACa) and NaHC0,-extractable P (AP,), respectively. The total fertilizer phosphate dissolved (AP) was calculated from ACa values based on the assumption that dissolution of PR released amounts of Ca and P in a constant ratio determined by the stoichiometry of the PR. AP increased with increasing content of < 45 pm particles. APb also increased with the percentage of < 45 pm fraction, with about 20% of AP being recovered as APb. A smaller proportion of dissolved P was soluble in NaHCO, for the soil comprising only the <45 pm particles. The increase in AP with increased percentage of < 45 pm soil was probably due inter alia to the greater P-sorption, Ca-sorption and the pH buffering capacity of the fine grained soil constituents.

A new approach to the determination of phosphate rock dissolution in organic soils using graphite furnace atomic absorption spectrophotometry

“…6). This is in agreement with the results reported by several workers (Khasawneh and Doll, 1978;Kanabo and Gilkes, 1988;Hanafi and Syers, 1994 …”

Analysis of Phosphate Rock Dissolution Determining Factors Using Principal Component Analysis in Some Acid Indonesian Soils

“…The P-retention capacity of the soil provides a sink for H 2 PO 4 2 released from a PR (Hanafi and Syers 1994), whereas clay content has been shown to correlate well with P-retention capacity (Olsen and Watanabe 1963). Soil textures such as clay play a significant role in the rate of transformation of the P nutrient (Kanabo and Gilkes 1988). The contribution of SAF (43%) was next to that of STF among the soil factors and showed a significant negative contribution (P 0.05), suggesting the importance of soil acidity status as a result of addition of PR for P dissolution as the second-degree term.…”

“…The soils were air dried and sieved (,2 mm) before use. The following chemical properties of the soils were determined: organic carbon (C) content (Walkley and Black 1934), pH in water using a soil/solution ratio of 1 : 5, P-retention capacity (Saunders 1965), Ca-exchange capacity by extraction with 0.10 M KNO 3 of the Ca sorbed from 0.025 M CaCl 2 (Mackay et al 1986), estimation of plant-available P by extraction with 0.5 M NaHCO 3 (Olsen et al 1954), and pH buffering capacity by pH titration (Kanabo and Gilkes 1988). Some of physicochemical characteristics of the soils are given in Table 2. The CPR, GPR, and CiamisPR were added to separate plastic containers containing 200 g of air-dried soil at a rate of 500 mg P kg 21 soil, thoroughly mixed, and incubated at 258C.…”

“…Several studies have shown that the effectiveness of PR is largely determined by the extent of dissolution of PR in moist soil. Dissolution of PR is influenced by many factors, including pH and pH buffering capacity of soil, soil texture, humic acid, P status such as available P and P-retention capacity, calcium (Ca) status such as calcium exchange capacity and exchangeable Ca, root systems, and the presence of arbuscular mycorrhizal (AM) fungus (Bangar et al 1985; Kanabo and Gilkes 1988;Robinson and Syers 1990;Acea and Carballas 1990;Bolland et al 2001; Barea et al 2002;Sikora 2002). Simple and multiple regression analysis of experimental data indicated that no single soil property adequately predicts PR dissolution in the soil, which supports the conclusions of several investigators for many soils from several countries Gilkes 1986, 1994;Wright et al 1992;Bolland et al 2001).…”

Characteristics of phosphate rock materials and their dissolution in some acidic Indonesian soils

“…The soil were air dried and sieved (5 2 mm) before use. The following chemical properties of soil were determined: Organic carbon content (Walkley & Black 1934), pH in water at a soil/ solution ratio of 1:5; P retention capacity (Saunders 1965), Ca-exchange capacity by extraction with 0.10M KNO 3 of the Ca sorbed from 0.025M CaCl 2 ), estimation of plant available P by extraction with 0.50M NaHCO 3 (Olsen et al 1954) and pH buffering capacity by pH titration (Kanabo & Gilkes 1988). The CPR, GPR, and CiamisPR were added to separate plastic containers containing 200 g of air dried soil at a rate of 500 mg P kg 71 soil, thoroughly mixed, and incubated at 258C.…”