EFFECTS OF VARIOUS SOIL EXCHANGEABLE CATION RATIOS ON GROWTH AND CHEMICAL COMPOSITION OF CITRUS PLANTS

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Abstract
Hanford sandy loam and Yolo loam, having exchange capacities of 15.0 and 18.8 me./100 g., respectively, were used to prepare soils with exchangeable cation ratios varying from 47 to 84% Ca 2 to 28% K, <1 to 28% Na, O to 17% NH4, O to 33% H, and base saturated soil containing excess CaCO[image]. In these soils growth of citrus seedlings (sour and sweet) was slightly reduced by 15% exchangeable K and by excess CaCO[image], and was appreciably reduced by 28% K, 14% Na, and 10 to 17% exchangeable NH4. Tomato and barley plants, tested for comparison, grew welfat all exchangeable cation ratios tested. In all tests the first crop of orange seedlings reduced growth of a second crop, but the reducing effect was least in soils containing approximately 4 to 8% K, in soils containing little Na, and in slightly to moderately acid soils. K and Na were equally effective in reducing Ca and Mn absorption by the citrus seedlings. Mn was reduced to the deficiency level by 15% K, by 7% Na plus 8% K, and by addition of 0.5% CaCO3 to basesaturated soil. Mg absorption was not appreciably reduced by Na or K until the 28% level was attained. Leaf and root K was increased by exchangeable Na. Increase of exchangeable K or Na in soil from <1 to 28% decreased Ca absorption by tomato and barley plants but had little effect on Mg uptake. Low percentages of Na slightly increased K absorption by these plants, but the higher percentages decreased the K content.