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Print version ISSN 0006-8705

Bragantia vol.24 no.unico Campinas  1965 

A análise foliar na nutrição do milho. II — Resultados de ensaios de adubação com N-P-K-S e micronutrientes1


Leaf analysis in corn plant nutrition. II — Progress report on N-P-K and minor elements studies



J. Romano Gallo; Rúter Hiroce; Luiz T. de Miranda




Several field trials of a NPK central composite design (Box) carried out in different corn growing areas of the State of São Paulo, showed that the composition of leaves collected 60 days after planting gave valuable indication of the nutrient status of the plant. In these experiments five levels of treatment of each N,P2O5, and K2O were used.
High positive correlations were found between leaf N or P and yield. A regression equation for per cent grain yield (y) on the mineral concentrations on dry basis in the leaves (x) were calculated being: nitrogen, y = 2.58 + 26.94 x; and phosphorus, y = 53.35 + 121.11 x. The wider range in values found in the leaf content of potassium for ten experiments (table 1) suggests possible effects of the soil type where they were grown.
Under the conditions of these studies, the following critical indices of composition on dry basis in corn leaves were established: Nitrogen, 2.90 per cent; phosphorus, 0.220 per cent; and potassium, 2.10 per cent. These values refer to the basal third of the leaf +4, the midrib being discarded (2).
The effect of sulfur was studied in plots receiving a central dose of 60 kg per hectare of each N or P2O5, and 30 kg per hectare of K2O but with no sulfur compared with those receiving 40 kg S per hectare. The diagnosis of sulfur nutrition requires further investigation. However, a value of approximately 200 ppm SO4-S in leaves or less should be indicated as a reference point for sulfur fertilization.
Nitrate nitrogen content in the midribs of leaves associated with high yields varied according to the soil type from 400 to 2200 ppm NO3-N. The great dependence of the nitrate content on soil-climatic conditions aggravated the evaluation of nitrate nitrogen nutrition for corn, using an average normal level or a narrow range of values. This would limit nitrate interpretation to areas of corn sited on the same region.
The data presented in table 2 show the effects of soil applications of manganese, zinc, copper, boron and molybdenum in a 25 factorial combination on the micronutrient composition of leaves and corn yield.
The contents of micronutrients in plant leaves depend on the level of soil fertility, antagonism and other interelationships of micronutrient elements, besides the fertilizers supply of the element itself. This emphasizes that a knowledge of these questions is needed in the utilization of tissue analyses data.



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Recebida para publicação em 23 de maio de 1965.



1Trabalho apresentado à VI Reunião Brasileira de Milho, realizada em Campinas e Piracicaba, São Paulo, de 10 a 13 de maio de 1965. Executado com auxilio da Fundação de Amparo à Pesquisa do Estado de São Paulo.

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