Wednesday, November 15, 2006

Sulfur fertilization in soybean.

Roberto E. Brevedan, Departamento de Agronomia, Universidad Nacional del Sur y CERZOS (CONICET), Altos del Palihue, Bahía Blanca, 8000, Argentina, Hugo R. Mirassón, Facultad de Agronomía, Universidad Nacional de La Pampa, Santa Rosa, 6300, Argentina, I. Rosana Palomo, CERZOS (CONICET), Altos del Palihue, Bahía Blanca, 8000, Argentina, María N. Fioretti, Departamento de Agronomía, Universidad Nacional del Sur, Altos del Palihue, Bahía Blanca, 8000, Argentina, and Sandra S. Baioni, Departamento de Agronomia, Universidad Nacional del Sur, Universidad Nacional del Sur, "Bahia Blanca, Buenos", 8000, ARGENTINA.

Due to the large expansion of the soybean area in Argentina more and more low productive soils are sown with the crop. One of the limiting factors is sulfur deficiency. Soybean response to S is related to the level of organic matter, the degree of erosion and the structural stability of the soil. An inadequate supply of S to the crop not only reduce its economic yield but it is also an important factor on the quality of the crop. Sulfur affects the quantity and composition of the proteins and participates in the synthesis of many secondary compounds in the plants. Field experiments were conducted at Tres Picos (38°20’S, 62°15’W) and at Santa Rosa (36°34’S, 64°16’W). The experimental plots were arranged in a completely randomized design with five replications. Plots were 6-m long with six rows spaced 0.50 m apart and with a plant population of 450,000 pl ha-1. Soybean cvs. A 3901 and A 3302 were sown on December 15. There were two treatments a) control, without fertilization and b) fertilized with 20 kg S ha-1. Leaf and stem S content were determined at R2 and R5 growth stages. There was an increase in stem-S content and a smaller increase in leaves-S content with fertilization. It was also observed that the S content in leaves and stems decreases with age, S concentration in leaves were 3.2 and 1.6 g kg-1 at R2 and R6, respectively. In the S-fertilized treatment yield and oil content were higher and protein lower than the non fertilized treatment.