Disponibilidade de zinco para as culturas do milho, sorgo e soja em Latossolo Vermelho-Escuro argiloso

Two field experiments were carried out on a Typic Haplusthox (clayey, kaolinitic, isohyperthermic) originally under cerrado vegetation, to evaluate the effects of zinc on maize  (Zea mays L.), sorghum ( Sorghum bicolor (L.) Moench), and soybean  ( Glycine max (L.) Merrill) yields and the effect of pH on zinc availability to maize. In the first experiment the main plots received, once only, 0, 1, 3, 9 and 27 kg/ha of zinc broadcast. The subplots were sown in the first year with three maize genotypes; in the second year, only 'Cargill 111’ maize was sown; in the third year. 'Cargill 111’ and RS 610 sorghum were sown, while in the fourth year 'Cargill 111’and ‘lAC-2’ soybean were sown. The 3 kg/ha rate was sufficient to maintain near-maximum maize yield for at least four consecutive crops. For 'Cargill 111’maize the soil critical levels were 1.4 ppm, 1.0 ppm and 0.7 ppm for the 0.1N HCl, 0.05N HCl + 0.025N H 2 SO 4 , and DTPA-TEA extractants, respectively. In the second experiment, 75, 15 and 22.5 t/ha of lime and 0.3, and 9 kg/ha of zinc were applied in a factorial design. The pH increase decreased maize yields.