Residual Value of Fertilizer Phosphorus in Selected Kansas Soils
1991
Pothuluri, Jairaj V. | Whitney, David A. | Kissel, David E.
Quantification of the factors affecting availability of applied P in soils would improve fertilizer-P recommendations for maximum P efficiency. A greenhouse study was conducted to determine the soil-test P drawdown with cropping, apparent fertilizer-P recovery, and plant-available P in selected Kansas soils. The 55 soils (0–15 cm layer), which ranged widely in soil-test P concentrations and other properties, received either no P or 100 mg P kg⁻¹ soil. Soils were cropped sequentially with perennial ryegrass (Lolium perenne L.) and ‘Honey Chow’ hybrid sorghum-sudan (Sorghum bicolor [L.] Moench). Linear P drawdown slopes (Bray and Kurtz no. 1 P/Cumulative P removal) for 20 unfertilized soils (initial Bray and Kurtz no. 1 P, >28.0 mg P kg⁻¹) were less than those for the same fertilized soils. The P drawdown rate for soils already high in indigenous available P was 1.4 to 1.8 times greater with P fertilization than without. Apparent fertilizer-P recovery (fertilized — unfertilized P uptake/fertilizer P added) for 48 noncalcareous soils was from 8 to 67%. Initial Bray and Kurtz no. 1 P concentration alone accurately predicted the plant-available P until the soil test dropped to 15 mg kg⁻¹ for 23 unfertilized soils (R² = 0.83). The R² increased to 0.91 when interacting variables of organic matter and silt were included. Contribution no. 90-453-J from the Kansas Agric. Exp. Stn.
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