Sulphur Content of Soils and Its Relation to Plant Nutrition

Abstract

1. The Alabama, Maryland, and Oklahoma soils analyzed are low in sulphur, phosphorus, and organic matter; the phosphorus being not much greater in amount than the sulphur. The central states soils are better supplied, on the average, in all three respects, and decidedly better supplied with phosphorus than with sulphur. Some of these soils might be considered to have a fair amount of sulphur, phosphorus, and organic matter, while others are deficient in these respects. The Chicago soils have a fairly good content of phosphorus, and a rather high content of sulphur and organic matter. Although the sulphate sulphur content of the Chicago soils is high, this accounts for little of the total sulphur, most of it being due to the large amount of organic matter present. 2. Most of the sulphur of soils is in organic form. There is a general correlation between the sulphur and organic matter content, soils of a high organic matter content having in general a high sulphur content. The surface soils are in general higher in sulphur than the subsoils. 3. Judging from the results obtained and the work of other investigators, sulphur fertilization should prove quite generally beneficial on the Atlantic coast and the Gulf coast. The same thing may be true of the Pacific coast. Sulphur fertilizers are probably not as generally needed in the central states, many soils no doubt needing them, and many others not. Soil of a high organic matter content, such as the Chicago soils, may not need sulphur fertilizers except for high sulphur-using crops. In case the sulphate sulphur is as great in amount as it is in the Chicago soils, sulphur fertilizers might not be needed, even if the organic matter content is low. Attempts are made, in the case of several soils, to correlate the sulphur, phosphorus, and organic matter content with the production of the soils, previous treatment, or other factors. 4. No definite conclusions can be drawn from the data as to the relation of sulphur to chlorophyll development in plants. This may come about through the effect of the sulphur in increasing the nitrogen content of the plants. 5. Flowers of sulphur and sodium sulphate, containing the same amount of sulphur as 100 pounds of gypsum per acre, and gypsum at rate of 500 pounds per acre, caused increased dry weights of sweet corn of 35-66 per cent. Larger amounts of flowers of sulphur and sodium sulphate gave no increases. The corn fertilized with sulphur had a higher moisture content than the controls. In the case of the gypsum series this amounted to 5 per cent.