Nitrogen fertilizing in corn based in chlorophyll meter reading and sufficiency index in nitrogen

Abstract

An experiment was carried out in Botucatu, state of São Paulo, Brazil, to evaluate the use of chlorophyll meter reading, in nitrogen necessity prediction in corn, Zea mays L., through a nitrogen sufficiency index (NSI). NSI was calculated at four (V⁴), seven (V₇), ten (V₁₀) leaves stage and in tasseling, dividing the measure of the chlorophyll meter reading in the plot by the measure in an area that received a high N rate (200kg N ha^-1). One day before the planting, 0 and 60kg ha^-1 were applied. (kg N ha^-1) were applied in plots that did not receive N: 0; 60 in V₄ and 40 in V₇; 42 in V₄ and 28 in V₇; 20 and 35kg N ha^-1 when the NSI < 0,95. (kg N ha^-1) were applied in plots that received N: 24 in V₄ and 16 in V₇; 20 and 35kg N ha^-1 when NSI < 0,95. The use of NSI allowed to define when N should be applied by starting from seven leaves stage.