Experimentos de adubação de milho doce e soja em solos de campo cerrado

Related are the increases in yields of sweet corn following application of lime and fertilizer applied at different rates and formulas in three locations approximately 600 km apart. The greatest increase, 13.8 tons per ha, was obtained in Brasilia, Federal District, in an extremely poor cerrado soil with two cultivated varieties, Cuban and Sweetangold. The smallest responses were obtained in an old cultivated soil in Matao, State of Sao Paulo. These were, respectively, 5.7 and 1.4 tons per ha for the Cuban and Sugar and Gold varieties. The highest yields were obtained in the cerrado soils of Brasilia. These responses indicated an overall need for phosphorus and zinc, with higher rates being required by the cerrado soils. Significant responses to nitrogen were obtained in all three locations, but only at the Experimental Station of Brasilia, near Planaltina in the Federal District, was any effect of potassium observed. Nevertheless, it appears necessary to guarantee an adequate level of potassium, as well as sulphur and magnesium, in the recommendations for liming and fertilization of these and other crops in soils studied. Fertilization increased the yield of soybeans seeded after the corn crop. In two of the locations these increases were from 80-250 to 3600-2750 kg per ha, showing a high residual effect of the fertilizers used, especially phosphorus.