Response of soybeans to acid soils and to aluminum and manganese on nutrient solution

Author

Marlon W. Yankee

Date of Award

12-1974

Degree Type

Thesis

Degree Name

Master of Science

Major

Plant, Soil and Environmental Sciences

Major Professor

Russell J. Lewis

Committee Members

W. L. Parks, G. M. Lessman

Abstract

Three greenhouse pot experiments were conducted to study the effects of soil pH, A1 and Mn on the growth of Forrest and Lee 68 varieties of soybeans (Glycine max L.). The effect of A1 and Mn in soils and in nutrient solution on nutrient concentrations in soybeans was also studied. The first study consisted of altering the pH values of three Tennessee soils (Huntington-Bewleyville silt loam, Jefferson loam, Leadvale loam) with additions of HCl or 3/4 Ca(OH)₂*1/4 MgO. Different amounts of acid or lime were added to change the pH of each soil to that of the other two soils. Levels of exchangeable A1 and various extractable fractions of Mn in the soil were measured and correlated with the con-centrations of Al, Mn, K, Ca, Mg, P, Mo and Bin the leaves of the soybeans. In the second study soybeans were grown in one-fifth strength Hoagland's Number Two nutrient solution in perlite. The nutrient solu-tions received added levels of 0.0, 4.0 and 8.0 ppm Al as Al₂(SO₄)₃ *18 H₂O and 0.5, 2.5 and 5.0 ppm Mn as MnCl₂. Concentrations of Al, Mn, K, Ca, Mg and P in the leaves were measured and correlated with the added levels of Al and Mn. The third study was conducted as the second but with 4.0, 12.0 and 20.0 ppm Al and 0.5, 1.5 and 3.0 ppm Mn in nutrient solution. Exchangeable Al and Mn in the soil decreased with increasing pH in each soil. The H₂O soluble and exchangeable fractions of soil Mn gave the highest correlation coefficients with the Mn concentration in the plant. At higher pH values soybean growth was greater on the Jefferson and Huntington-Bewleyville soils. At lower pH values these soils contained high levels of exchangeable Mn, which resulted in Mn toxicity. The effect of A1 in the soils was apparently masked by an acid-induced increase in P solubility in the soil. Manganese toxicity symptoms were associated with pH values of less than 4.7 and Mn leaf concentrations of greater than approximately 300 ppm. The concentrations of K, Ca and Mo in the plants grown on soils were variable. The Mg concentration in the plant generally increased with increasing pH while the B concen-tration tended to decrease with increasing pH. Perlite was a poor growth medium for the study of A1 in nutrient solutions due to an apparent ability to sorb and/or release A1 in solu-tions. A decrease in top weights of soybeans was the best indication of A1 toxicity in the nutrient solution studies. Percent Ca, Mg and P in the plant decreased as the A1 added to nutrient solution increased. Potassium concentrations varied directly with the A1 levels in the first study while they were variable in the second study. Forrest variety was more susceptible to Mn toxicity than Lee 68 variety. Manganese toxicity symptoms were associated with a Mn leaf concentration of greater than 125 ppm. Increasing Mn in nutrient solu-tion tended to decrease the percent Ca in the plant while percent K and Mg were unaffected. The effect of Mn on the percent P in the plant differed between varieties.

Recommended Citation

Yankee, Marlon W., "Response of soybeans to acid soils and to aluminum and manganese on nutrient solution. " Master's Thesis, University of Tennessee, 1974.
https://trace.tennessee.edu/utk_gradthes/8149