The absorption of mineral elements by forage plants. II. The effect of fertilizer elements and liming materials on the content of mineral nutrients in soybean leaves

1. The results of a study of factors affecting the absorption by soybeans of certain mineral elements of nutritional significance are presented. In general, in agreement with other contributions in this field, additions of cobalt, manganese, copper, and phosphorus to the soil culture resulted in increased concentration of the respective element in the plant tissue. 2. Calcium carbonate in large quantities did not significantly affect the absorption by the soybean of the cobalt naturally present in the soil. The absorption of water-soluble cobalt applied to the soil, however, was greatly reduced by liming. The absorption of soluble compounds of copper and manganese applied to the soil was influenced in the same way by liming. However, absorption of the naturally-occurring manganese in the soil was also reduced by liming. 3. Both phosphorus and iron absorption were reduced by liming, but this may have been a yield factor. In any case, the differences were small. 4. The calcium and iron contents of soybean leaves were reduced 50% by high rates of application of nitrogen and phosphate. This reduction was significantly related to the yield, however. 5. The contents of cobalt, copper, and manganese were reduced in soybean leaves at high levels of phosphate application. Nitrogen did not appear to affect the absorption of these elements. 6. A significant interaction between the effects of applications of phosphates and nitrogen on the phosphorus content of soybean leaves was observed. At low levels of nitrogen supply in the soil, applications of phosphorus increased the phosphorus content of the leaves. At high levels of nitrogen supply, no change occurred in the phosphorus content of the plant. 7. At high levels of both phosphorus and limestone supply, there was no evidence of any toxic effect on yields because of additions of micronutrient elements to the soil.