Correlation of a Resin Membrane Soil Phosphorus Test with Corn Yield and Routine Soil Tests

Most tests for plant‐available soil P are based on extraction with a chemical solution. Extraction of P through ion exchange could provide better estimates of plant‐available P. The objective of this study was to field calibrate a test based on a commercially available ion‐exchange resin membrane (RMP) and compare it with Bray‐P 1 (BP), Mehlich‐3 (M3P), and Olsen (OP) tests. Replicated P response trials with corn ( Zea mays L.) were established at 59 Iowa locations (78 site‐years). The soils represented 17 series of the suborders Argiudolls, Endoaqualfs, Endoaquolls, Hapludalfs, and Hapludolls. Initial BP, M3P, RMP, and OP values ranged from 2 to 63, 7 to 79, 6 to 63, and 3 to 31 mg P kg −1 , respectively. The r 2 values of relationships between soil P extracted across sites ranged from 0.84 to 0.91, and the lowest values were for BP relationships. The BP test measured less P in a CaCO 3 –affected soil with pH 8.1 but not when pH was ≤7.7. Excluding the calcareous site improved correlations only for BP. Critical concentration ranges defined by Cate‐Nelson (CN) and linear‐plateau (LP) models and relative yield responses for various soil‐test ranges indicated that 13 to 20 mg kg −1 for BP, 16 to 21 mg kg −1 for M3P, 13 to 19 mg kg −1 for RMP, and 8 to 11 mg kg −1 for OP corresponded to a 94 to 96% mean relative yield response. The sink‐based RMP test was as effective as routine P tests at predicting corn response to P fertilization and could be adopted for production agriculture.