Field Studies Evaluating Placement of Ion Exchange Resins to Assess Nutrient Availability In Desert Soils.

Commonly used soil analysis and resin capsule procedures successfully assess nutrient status in fertile agriculture soils, but their validity in desert ecosystems is not known. Previous studies suggest effectiveness of resin capsules may be related to the depth at which the resin capsules are placed. Field studies were established in Rush and Skull Valley, UT on clay loam and sandy loam soils, respectively. Thirty 1 m x 1 m plots were measured at each field site. Resin capsules were placed at depths of 0-5 cm, 5-10 cm and 10-15 cm in the soil and fertilizer was applied with six N and P treatments (0, 5.6, 11.2, 22.4, 44.8 and 89.6 kg/ha) and six S treatments (0, 6.7, 13.4, 26.9, 53.8 and 107.5 kg/ha). Resin capsules were removed after ninety days incubation in late summer and then again in the spring. Soil samples were taken at the same depths. Data collected indicates that for NO3-N, P and S, conventional soil tests were more effective in distinguishing between fertilizer rates. For these nutrients, resin capsules were most effective at the 5-10 cm placement. For NH4-N, resin capsules and conventional soil tests were equally effective in distinguishing between treatments. The best placement for resin capsules for NH4-N was 0-5 cm.