Orthophosphoric Acid as a Phosphorus Fertilizer in Trickle Irrigation

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Abstract
Traditional P fertilizers have demonstrated relative immobility in soils. When used in trickle irrigation, these fertilizer materials tend to form precipitates in the irrigation lines which cause clogging problems and eventual breakdown of the system.The movement of P in Superstition sand was determined after spot placement of treble superphosphate (TSP) and injection of orthophosphoric acid (OP) with a trickle system. Rates of P application, based on the recommended rate of TSP for citrus in the Yuma, Arizona area were: check, 28 kg P/ha as TSP and 14, 28, 57, and 114 kg P/ha as OP. The experiment was conducted over the two irrigation periods; one for 3 days and the second for 24 days. Phosphorus was delivered to a greater soil volume when applied as OP than TSP, which should result in more plant available P in the root zone. The OP treatments lowered the pH of the irrigation water enough to eliminate clogging problems of P precipitates in the irrigation lines.
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