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Effect of Nitrogen, Potassium, Calcium, and Magnesium on Mineral Composition of Lakeland Fine Sand in Relation to Mineral Content of Tung Leaves¹

ABSTRACT

Eight-year-old tung trees growing on Lakeland fine sand were treated from 1949 to 1955 with factorial combinations of 3 sources of N and 2 levels each of N, K, Ca, and Mg. Soil samples collected in October 1954 showed that exchangeable K was increased to a depth of 36 inches (lowest depth sampled) by the high level of applied K, but was reduced by the high level of Mg. Exchangeable Ca was increased by the high level of Ca, but was reduced by the high level of K or Mg. Exchangeable Mg was increased by the high level of Mg in the 0- to 6-inch depth only. Below 6 inches, it was reduced by the high level of K or Mg.

The chemical analyses of leaves collected in 1955 show the same general trends as those found in the soil. The polynomial equations of degrees n = 1, 2, 3, and 4 were calculated for the regression of the concentration of K, Ca, and Mg in the leaves on saturation percentage of these elements in the soil. The linear equation for K was significant for each soil depth and the equations of higher degree show no significant improvement. The linear equations for Ca were significant at all depths, but the second-degree equations were an improvement on the linear in the top 18 inches of soil. The linear equations for Mg were significant in the top 18 inches of soil. The second-degree equations were an improvement on the linear in the 6- to 12- and 12- to 18-inch depths.

¹ Contribution from the Crops Research Division, ARS, USDA, and the Florida Agr. Exp. Sta., Gainesville. Presented before Div. IV, Soil Science Society of America, Atlanta, Ga., Nov. 22, 1957.

² Associate Plant Physiologist and formerly Senior Soil Scientist, respectively, Crops Research Division, ARS, USDA, Gainesville, Fla.

Received for publication January 22, 1958. Accepted for publication April 16, 1958.