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THE CHEMICAL FACTORS INFLUENCING PHOSPHORUS MOBILITY AND AVAILABILITY IN COARSE TEXTURED SOIL
Abstract
The downward movement of phosphorus is significant for irrigated coarse textured soils that are low in organic matter content. A laboratory study with columns of Valentine loamy sand (Typic Ustipsament) was conducted to determine the effects of ionic strength, solution pH, and cation and anion source of a neutral salt leaching solution on P distribution with depth. Solutions of the chlorides of K, Na, and Li at concentrations of 1.0, 10('-2), 10('-4) and 10('-6) mol L('-1) were added to a set of 40 cm soil columns, after a surface application of diammonium phosphate (DAP) at a rate of 0.30 grams/column. To a second set of 40 cm columns, solutions of KCl at concentrations of 1.0, 10('-2), 10('-4), and 10('-6) mol L('-1) and solution pH 4.0, 6.0, and 8.0 were applied, after the surface application of 0.30 grams/column DAP. Solutions of KCl at concentrations of 10('-2) and 10('-4) mol L('-1) and distilled water were added to 180 cm soil columns which received surface applied DAP at either a 0.30 or 0.72 grams/column rate. Solutions of the potassium salt of F, Cl, So(,4), and CO(,3) at a concentration of 10('-2) mol L('-1) were added to 120 cm soil columns, after an application of 0.30 grams/column of DAP on the surface of each column. For each experiment after 500 ml of solution had been added to each column, the columns were sectioned and the amount of extractable P in each section was measured. Results of these experiments indicate that the ionic strength of the leaching solution, not the monovalent cation source, strongly influenced the total amount of extractable P in the soil column. The total amount of extracted P increased with ionic strength, while downward P movement was reduced. Solution pH did not influence the total amount of P extracted from the soil column. The extractable P distribution within the soil column was influenced by the ionic strength and solution pH of the leaching solution and the amount of NH(,4)('+) applied to the soil. Organic matter coatings are suspected of undergoing conformational transitions, depending on the composition of the soil solution. These structural transitions influence the amount of organic compounds in the soil solution and consequently the distribution of extractable P in the soil.
Subject Area
Agronomy
Recommended Citation
EVANS, ANDREW, "THE CHEMICAL FACTORS INFLUENCING PHOSPHORUS MOBILITY AND AVAILABILITY IN COARSE TEXTURED SOIL" (1983). ETD collection for University of Nebraska-Lincoln. AAI8404812.
https://digitalcommons.unl.edu/dissertations/AAI8404812