Plant availability of p in commercial superphosphate fertilizers
Titel:
Plant availability of p in commercial superphosphate fertilizers
Auteur:
Mullins, G. L.
Verschenen in:
Communications in soil science and plant analysis
Paginering:
Jaargang 19 (1988) nr. 13 pagina's 1509-1525
Jaar:
1988-10
Inhoud:
The quality of phosphate rock (PR) is declining and the use of lower quality PR results In lower water-soluble and higher citrate-soluble P in the fertilizer product. A greenhouse study was conducted to evaluate the plant availability of P in commercial superphosphate fertilizers having various levels of water-soluble P. Seven commercial fertilizers, Including 6 granular concentrated superphosphates and one normal superphosphate, were evaluated. Reagent grade monocalcium phosphate served as a control. The fertilizers were manufactured from PR deposits located in the United States (Florida, Idaho and North Carolina) and Morocco. Water-soluble P ranged from 77 to 92 X of the total fertilizer P. Citrate-soluble, water-insoluble P ranged from 7 to 20 % of the total fertilizer P. Four of the 5 American fertilizers had a lower percentage of water-soluble P as compared to the concentrated superphosphate from Morocco. Fertilizers manufactured from U.S. phosphate deposits contained an average of 6 times more Fe and 4 times more Al than the Moroccan concentrated superphosphate. Each source was added to a Mountvlew slit loam soil (pH = 6.5) at rates to supply 0, 10, 20, 30, 40 and 50 mg P kg-1soil (0, 22.9, 45.8, 68.7, 91.6, and 114.5 ppm P2O5, respectively). Sorghum-sudangrass (Sorghum bicolor) was harvested at 28 and 56 days after planting in the treated soil. Herbage yields and the P concentration in harvested forage were not affected by the source of added P. The effect of the rate of added P on forage yield and P concentration was described by polynomial regression. The granular concentrated superphosphate fertilizers used in this study contained ≥ 80 % of their plant available P in a water-soluble form and were as effective as reagent grade monocalcium phosphate. Thus the level of water-soluble P that will be required to reduce the performance of a fertilizer is lower than the levels currently found in American commercial concentrated superphosphates
Tijdschrift beschrijving