Levantamento do estado nutricional de canaviais de São Paulo, pela análise foliar

Estudo da composição das folhas de cana-planta e de cana-soca de primeiro corte, em diferentes regiões canavieiras do Estado de São Paulo. Amostras de duas variedades, em duas idades, de cana-planta, e numa de soca, foram analisadas para doze elementos: N, P, K, Ca, Mg, S, B, Cu, Fe, Mn, Mo e Zn. Pelo levantamento nutricional foi feita a distribuição dos teores de cada elemento, por freqüência. A evidência das variações na composição das fôlhas, permitiu a interpretação das análises com base nas faixas críticas de teores admitidas para cada amostragem e variedade. Os elementos K, Mg, N, P, S e Fe foram os que apresentaram maior porcentagem na faixa de carência. A leaf analysis survey of sugar cane plantations in São Paulo was conducted with twelve essential plant nutrients. These included sulfate--sulfur and total N, P, K, Ca, Mg, Fe, Mn, Cu, Zn, B and Mo. Samples consisting of leaf blades +3 for the 2 major commercial varieties Co. 419 and CB. 41/76 were collected in 32 counties from 89 fields when the cane was 4 and 9 months old, and from 69 groves of the ratoon cane crop, when 4 to 5 months of age. The analyses were carried out on the 8 middle inches of the leaf blades. Only lamina was used. The results indicated clear-cut differences in leaf-nutrient contents attributed to the following variables: age of the cane at sampling, type of crop (plant or ratoon canes) and varieties. In general, the ranges in the levels of the elements in the blades for both varieties in all locations were very wide. Nitrogen had the smallest and molybdenum the largest variation, among the different nutrient elements analyzed. Based on the frequency distribution of leaf nutrient content, it was noted that a higher percentage of sugar cane plantations was found to have lower levels in the following decreasing order: K, Mg, N, P, S and Fe.