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Adsorption and Desorption of Phosphorus and Nitrogen by Immersed Stalks

Gilley, J.E., Eghball, B., Marx, D.B.
Transactions of the ASABE 2009 v.52 no.2 pp. 429
phosphorus, nitrogen, phosphates, nitrate nitrogen, ammonium nitrogen, adsorption, desorption, crop residues, stems, Glycine max, soybeans, Triticum aestivum, wheat straw, Zea mays, corn stover, pollution control, agricultural runoff, overland flow
Adsorption and desorption of phosphorus (P) and nitrogen (N) by stalk residues may influence the concentrations of P and N in runoff. A laboratory study was conducted to measure the effects of P and N constituents in solution on adsorption and desorption of P and N by corn, soybean, and wheat stalk residues. Experimental variables included type of stalk material (corn, soybean, and wheat), inorganic nutrients in solution (PO₄-P and NO₃-N; PO₄-P and NH₄-N; NO₃-N and NH₄-N; and PO₄-P, NO₃-N, and NH₄-N), solution concentration (0, 6, 12, and 24 microgram g -1 residue), and stalk immersion period (25, 250, 2500, 25000, and 86400 s). The initial concentration of each of the P and N constituents in a particular test solution was the same (0, 6, 12 or 24 microgram mL -1 ). Corn-stalk residues released PO₄-P, NO₃-N, and NH₄-N. The quantity of PO₄-P released generally increased as the length of time the corn stalks were immersed became greater. The presence of P and N constituents in solution in general did not affect the quantity of NO₃-N released by corn-stalk residues. Soybean-stalk residues released PO₄-P and adsorbed relatively small amounts of NH₄-N. Wheat-stalk residues released PO₄-P, and adsorbed NO₃-N and NH₄-N. The presence of stalk residues, P or N solution concentration, and residue immersion period may influence P and N concentrations of overland flow. The amount of P and N adsorbed or desorbed by residue materials can be significantly different if more than one nutrient constituent is present in solution.