The Requirement for Water-Soluble Phosphorus in Acidulated Phosphates Containing Fe-Al-P
Compounds as Influenced by Soil pH. (3448)
Authors:
L.I. Prochnow* - Univ. of Sao Paulo, Brazil S.H. Chien - IFDC, Muscle Shoals, AL G. Carmona - IFDC, Muscle Shoals, AL J. Henao - IFDC, Muscle Shoals, AL E.F. Dillard - IFDC, Muscle Shoals, AL E.R. Austin - IFDC, Muscle Shoals, AL
Abstract:
Use of low quality phosphate rock can result in high amounts of water-insoluble P compounds in fertilizers. This study was conducted to determine the requirements of water-soluble P (WSP) in four acidulated phosphate fertilizers containing
Fe-Al-P compounds. Fertilizer samples, in the original form and water-leached, were: (1) analyzed for total amounts of Fe, Al, Si, Ca, Mg, K, Na, Ti, Ba, Sr, Zn, P, F and SO42-, and (2) scanned with an X-ray diffractometer looking for chemical species present. A modal analysis was used to estimate the composition of the fertilizers. Mixtures of water-soluble monocalcium phosphate and the
water-insoluble fertilizer residues were prepared to give a wide range of WSP.
Fertilizer mixtures were applied to supply 40 mg AOAC available P per kilogram of a thermic Rhodic kanhapludults with pH values of 5.2 ± 0.05 (not limed) and 6.4
± 0.08 (limed). Wheat was cultivated for 100 days. The requirement for WSP was source and pH dependent. At a soil pH of 5.2, the fertilizers required 73% to 95%
WSP to reach the maximum dry-matter yield, while at pH 6.4 the fertilizers required 60% to 86% WSP. All fertilizers required less than 50% WSP to reach 90% of the maximum yield. Lower levels of water-insoluble P, as compounds of the type Fe-Al-P, was tolerated in acidulated P fertilizers when applied to acid soils.
The results confirm no reason for legislations imposing high WSP fertilizers for all P sources and agronomic conditions.
Speaker Information: Luis Prochnow, Univ. of Sao Paulo, Brazil, Dept. of Soil and Plant Nutrition, ESALQ/USP, P. O. Box 09., Piracicaba, SP 13418-900; Phone: 19 3429 4171; E-mail: [email protected]
Session Information: Tuesday, November 2, 2004, 9:00 AM-11:00 AM Presentation Start: 9:00 AM (Poster Board Number: 1740)
Keywords: Phosphate fertilizers; Phosphate rock; Water-Soluble P; Impurities in Fertilizers