Availability of Sulfur to Rice Plants in Submerged and Upland Soil

A deficiency disease of rice occurred on plants grown in Evesboro soil in pot culture, following submergence as customarily employed for lowland rice culture. This was apparently sulfur deficiency, since rice plants responded to various forms of sulfate sulfur in further pot tests. In comparison experiments, sulfur uptake by rice plants was reduced by submerging the soil. In one experiment testing 5 levels of available sulfur in Evesboro soil, parabolic and logarithmic equations were solved for the relationship between plant uptake of sulfur and available sulfur in the soil. When both types of equations were solved for the best fitting values of soil sulfur, the values obtained in submerged and upland soil were comparable, indicating that both soil and fertilizer sulfur were subject to the same changes upon flooding. In comparisons of submerged and upland conditions on five other soils, sulfur uptake was lowered by flooding the soil, regardless of the type of yield response, whether negative or positive, obtained from flooding. Sulfur percentage in the plants grown in flooded cultures was related to the yield response obtained from flooding. The soils which gave negative yield responses produced the lowest sulfur contents. In further experiments, organic matter, in the form of dried and ground rice plant tissue, when added to flooded cultures, depressed the growth of rice plants. Sulfate, added along with the organic matter, overcame to various degrees the depression in growth. Prior submergence also had an ameliorating effect on the growth depression which occurred with flooding and organic matter.