Comparing Nutrient Availability in Low-Fertility Soils using Ion Exchange Resin Capsules

• Published in: Communications in Soil Science and Plant Analysis 2012, Vol.43 (1-2), p.368-376
• Main Authors: Jones, Mary P, Webb, Bruce L, Cook, Daniel A, Jolley, Von D
• Format: Article
• Language: English
• Subjects: agricultural soils; Agronomy. Soil science and plant productions; Ammonium; ammonium nitrate; Biological and medical sciences; clay; conventional soil tests; desert soils; ferrous sulfate; field capacity; Fundamental and applied biological sciences. Psychology; hydrochloric acid; ion exchange resins; iron; nitrate; nitrogen; nutrient availability; phosphoric acid; phosphorous; phosphorus; phosphorus fertilizers; resin capsules; sand; sodium bicarbonate; soil analysis; soil incubation; Soil science; soil treatment; sulfur; zinc; zinc sulfate
• ISSN: 1532-2416; 0010-3624; 1532-2416; 1532-4133
• DOI: 10.1080/00103624.2012.641790

Assessing the nutrient status of low-input, low-fertility desert soils poses some unique challenges. Commonly used soil analysis procedures and resin capsules generally assess nutrient status of fertile agricultural soils. Ion-exchange resin capsules (Unibest Company, Bozeman, Mont.) provide a viable alternative. A study was conducted to determine effectiveness of resin capsules to extract low levels of nutrients applied to native soils. Loamy sand and sandy clay loam desert soils from Utah were treated with combinations of four rates of nitrogen (N) as ammonium nitrate (34–0–0), three rates of phosphorus (P) as phosphoric acid (0–72–0), and two rates of iron sulfate (FeSO₄·7H₂O) and zinc sulfate (ZnSO₄·7H₂O) (include an untreated control). Each soil treatment was implanted with a resin capsule placed into either 250 or 1000 cm³ of soil after addition of water equivalent to 50% field capacity and incubated for either 60 or 120 days at 25 °C. After the appropriate incubation time, capsules were washed and extracted using 2 M hydrochloric acid (HCl), and the extract was used to measure iron (Fe), ammonium (NH₄)-N, nitrate (NO₃)-N, sulfur (S), and zinc (Zn). Conventional soil tests were completed on incubated soils (60 or 120 days). Resin capsules reflected NH₄-N and P fertilizer applied at low rates in the loamy sand but not in the sandy clay loam. Neither Fe nor Zn application was reflected in resin capsules, but the accompanying S was clearly quantified. In comparison to conventional soil test procedures, resin capsule NH₄-N was clearly a better indicator than KCl-extractable NH₄-N; resin capsule NO₃-N was effective, but not as good an indicator as water extraction; and resin capsule P was reflective of soil applied P in loamy sand but not in sandy clay loam, whereas sodium bicarbonate was effective in both soils. Resin capsules show promise for use in low-input conditions, but additional understanding of interactions in variable soils is needed.