Phosphorus Fertilizer Residual Effects on Irrigated Crops in Rotation
1965
Campbell, R. E.
Residual effects for 8 years of 0, 26, 52, 105, and 210 lb of P per acre applied for barley were measured in a 6-year rotation of barley, alfalfa (3 years), corn, and sugar beets grown on Thurlow clay loam. Amounts of P removed by crops in 9 years totaled 96, 109, 124, 136, and 179 lb, respectively. Corresponding recoveries of applied P were 49, 54, 38, and 40%. Most of the 26 pounds of P was used in 4 years. Residual response over the entire period increased with higher rates. Residual P soluble in NaHCO₃ decreased with continued crop removal of applied P. The results of this experiment which was located in Montana agreed well with similar experiments run concurrently in New Mexico, Oregon, and South Dakota. The differences among them can be reconciled on the basis of soil textural differences as they affect P adsorption and availability.
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