Development of a DTPA Soil Test for Zinc, Iron, Manganese, and Copper

Abstract

A DTPA soil test was developed to identify near‐neutral and calcareous soils with insufficient available Zn, Fe, Mn, or Cu for maximum yields of crops. The extractant consists of 0.005M DTPA (diethylenetriaminepentaacetic acid), 0.1M triethanolamine, and 0.01M CaCl2, with a pH of 7.3. The soil test consists of shaking 10 g of air‐dry soil with 20 ml of extractant for 2 hours. The leachate is filtered, and Zn, Fe, Mn, and Cu are measured in the filtrate by atomic absorption spectrophotometry.The soil test successfully separated 77 Colorado soils on the basis of crop response to Zn, Fe, and Mn fertilizers. Critical nutrient levels must be determined separately for each crop using standardized procedures for soil preparation, grinding, and extraction. The critical levels for corn using the procedures reported herein were: 0.8 ppm for Zn, 4.5 ppm for Fe, and tentatively 1.0 ppm for Mn, and 0.2 ppm for Cu.Development of the soil test was based, in part, on theoretical considerations. The extractant is buffered at pH 7.30 and contains CaCl2 so that equilibrium with CaCO3 is established at a CO2 level about 10 times that of the atmosphere. Thus, the extractant precludes dissolution of CaCO3 and the release of occluded nutrients which are normally not available to plants. DTPA was selected as the chelating agent because it can effectively extract all four micronutrient metals. Factors such as pH, concentration of chelating agent, time of shaking, and temperature of extraction affect the amount of micronutrients extracted and were adjusted for maximum overall effectiveness.

Assessing soil properties and nutrient availability under conservation agriculture practices in a reclaimed sodic soil in cereal-based systems of North-West India

“…The available N in soil was determined by alkaline permanganate method (Subbiah and Asija 1956), available phosphorus (P) by ascorbic acid reductant method of Olsen et al (1954), available potassium (K) by flame photometer using neutral 1 N ammonium acetate extractant as described by Jackson (1973), available sulphur (S) by turbidimetric barium chloride procedure as described by Chesnin and Yien (1951). Available (DTPA-extractable) Fe, Mn, Zn and Cu of the soil samples were estimated by using atomic absorption spectrophotometer (AAS) following the method of Lindsay and Norvell (1978). …”

Uptake of cadmium from an experimentally contaminated calcareous soil by arbuscular mycorrhizal maize ( Zea mays L.)

“…The soil had the following properties (dry matter basis): pH (soil:water ratio 1:2.5) 8.67, 0.30% organic matter, 0.018% Kjeldahl-N, 3.4 mg kg -1 of 0.5 mol l -1 NaHCO 3 -extractable P (Olsen et al 1954;Murphy and Riley 1962), and 33.6 mg kg -1 of 1 mol l -1 NH 4 OAc-exchangeable K. Soil-extractable trace element concentrations were: 4.96 mg kg -1 Fe, 4.15 mg kg -1 Mn, 0.28 mg kg -1 Cu, 0.48 mg kg -1 Zn, and 0.06 mg kg -1 Cd. Soil metals were extracted with a 5 mmol l -1 diethylene triamine pentaacetic acid-10 mmol l -1 CaCl 2 -0.1 mol l -1 triethanolamine solution adjusted to pH 7.30 (Lindsay and Norvell 1978) and metal concentrations were determined using an atomic absorption spectrophotometer (Perkin Elmer Model 2100). Soil was passed through a 1-mm sieve, sterilized by autoclaving at 120 C for 2 h and then air-dried.…”

Assessment of biotransfer and bioaccumulation of cadmium, lead and zinc from fly ash amended soil in mustard–aphid–beetle food chain

“…A C C E P T E D M A N U S C R I P T digested in 20 ml of triacid mixture (HNO 3 /H 2 SO 4 /HClO 4 , 5:1:1) at 80 °C (Allen et al, 1986 for 2 hours (Lindsay and Norvell, 1978).…”