Characterization and Agronomic Evaluation of Single Superphosphates Varying in Iron Phosphate Impurities
Loading...
Date
2003
Journal Title
Journal ISSN
Volume Title
Publisher
Abstract
An increase in the concentrations of water-insoluble iron phos- The European Economic Community, for example, set phate (Fe-P) compounds in acidulated P fertilizers has raised the a minimum level of 93% of total available P (water concern that the agronomic effectiveness of these P fertilizers will citrate) as water-soluble P in fully acidulated P fertilizers decrease. This study was conducted to evaluate the agronomic effec- marketed in the European community (Anonymous, tiveness of three sources of single superphosphate (SSP) varying in 1975). Several researchers have found that the waterFe-P impurities for upland and flooded rice (Oryza sativa L.) grown insoluble fractions of acidulated P fertilizers after water for 55 d. A modal chemical analysis and X-ray diffraction were used leaching are lower in agronomic efficiency compared to characterize the SSP samples and their water-leached forms. A with the original fertilizers without leaching or MCP. greenhouse study was conducted where rates of 0, 5, 15, 30, 50, and The P availability of the isolated water-insoluble frac100 mg P kg1 as total available P (water plus citrate-soluble P) were tion depended on the types of P fertilizer produced from applied from each SSP source and monocalcium phosphate (MCP) different sources of PR (Bartos et al., 1991; Mullins et to a Hiwassee clay loam (thermic Rhodic Kanhapludult). The water- al., 1990; Prochnow et al., 1998). Gilkes and Lim-Nunez soluble P contents of the SSP sources were 46, 80, and 86% of the (1980) postulated that raw materials and manufacturing total available P (water citrate) corresponding to an increase of procedures should be chosen to limit the development Fe content (2, 4, and 7%) in the phosphate rock sources used for of impurities, mainly Ca(Fe, Al) H(HPO4)2F2 ·2 H2O and SSP production. The main Fe-P impurities in the SSP samples were (Fe, Al)(K, Na)H8(PO4)6 identified as Fe ·6H2O, in SSP and to minimize 3NaH8(PO4)6 ·6H2O and Fe3H9(PO4)6 ·6H2O. Single superphosphate with only 46% of water solubility was 91% as effective the content of apatite without substantially increasing the as MCP in increasing dry matter yield and 76% as effective for P cost of the fertilizer. Greenhouse and field studies, howuptake by upland rice. The other two SSP sources were as good as ever, have shown that the level of impurities in P fertilizMCP in effectiveness for upland rice. All of the SSP sources were ers produced in the United States would have to be equally as effective as MCP in producing dry matter yield and P increased above current levels before effectiveness of P uptake by flooded rice.
Description
Keywords
Phosphates