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Effect of Water‐Soluble Phosphorus on the Effectiveness of Triple Superphosphate Fertilizers
Author(s) -
Mullins G. L.,
Sikora F. J.,
Williams J. C.
Publication year - 1995
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1995.03615995005900010040x
Subject(s) - chemistry , monocalcium phosphate , fertilizer , phosphorus , reagent , phosphate , water soluble , ammonium phosphate , agronomy , solubility , phosphorite , biochemistry , organic chemistry , fishery , fish <actinopterygii> , fish meal , biology
Impure phosphate rock results in the formation of P‐containing impurities having low water solubility in commercial triple superphosphate (TSP) fertilizers, which may influence their effectiveness. A greenhouse study was conducted to determine the level of water‐soluble P needed in TSP to maximize plant P uptake and yield when applied to a slightly acid soil (pH = 6.4). Fertilizer impurities were isolated from four commercial TSP fertilizers as a water‐washed fraction by washing the whole fertilizers with deionized water. Fertilizers with varying water‐soluble P were simulated by mixing reagent‐grade monocalcium phosphate (MCP; ≈ 100% water soluble) with water‐washed fertilizer fractions or reagent‐grade dicalcium phosphate (DCP; ≈ 1.2% water‐soluble P). The mixtures contained 0, 20, 40, 60, and 80% of the available P (available = water‐soluble + ammonium citrate soluble P) as MCP. An additional treatment received 100% water‐soluble P as MCP. Mixtures were applied to supply 50 mg available P kg −1 soil. Sorghum‐sudangrass [ Sorghum bicolor (L.) Moench] was harvested 21 and 42 d after planting. Forage yield and P uptake were affected by P source and water‐soluble P content. Compared with using a 100% water‐soluble P source (MCP), individual TSP fertilizer materials required 52 to 66% water‐soluble P to attain 90% of the dry matter yield and 41 to 51% water‐soluble P to attain 90% of P uptake. Results of this study demonstrate that current levels of “water‐insoluble P” in commercial TSP sources are not affecting their performance when added to slightly acid soils.