Estudos sobre a nutrição mineral do sorgo sacarino (Sorghum bicolor (L) Moench). I: deficiências de macro e micronutrientes e toxidez de alumínio, cloro e manganês

Abstract

Sorgo sacarino, cv Brandes, foi cultivado em solução nutritiva deficiente em macro e micronutrientes e com excesso de alumínio, cloro e manganês. Foram obtidos sintomas das deficiências e excessos provocados no meio e o material foi analisado. Obteve-se uma estimativa das exigências nutricionais. Análises tecnológicas do colmo, mostraram os efeitos das deficiências de nitrogênio, fósforo e potássio sobre as mesmas.Sweet sorghum cv Brandes was grown in nutrient solution under stress of macro and micronutrients, as well as in the presence of toxic levels of Al, Cl and Mn. Symptoms of deficiency were observed in all cases, with the possible exception of Cu. Toxicity symptoms of the elements tested were also observed. As a rule, there was good agreement between abnormalities induced with those described in the literature for cereals. Dry matter production was affected in the following increasing order: -S = - Cu = - P = complete, -B, -Zn, -K, -Mo, -N, excess Mn, -Mg, excess Cl, -Fe, excess Al and -Ca. The following leaf contents correspond to deficiency level: N - 1.87%, P-0.14%, K-0.73%, Ca-0.40% (lower leaves) and 0.66% (upper leaves); S-0.16%; B-32 ppm (lower leaves) and 15 ppm (upper leaves), Cu-8 ppm; Fe-157 ppm (lower leaves) and 162 ppm (upper leaves); Mn-339 ppm (lower leaves) and 144 ppm (upper leaves); Mo-0.54 ppm; Zn-16 ppm. Leaf contents associated with toxicity symptoms were: Al-640 ppm; Cl-3.85%; Mn-1440 ppm, and, 1220, 2.37% and 445 ppm, respectively for lower and upper leaves. Nutrient requirements of weet sorghum were estimated to be in kg/ha: N-89.0, P-10.2, K-91.5, Ca-31.5, Mg-18.1, and S-11.6; in g/ha: B-90.0, Cu.61.0, Fe-1,704.0, Mn-256, Mo-2-4, and Zn-146. Only N and K significantly affected ethyl alcohol yield.