Abstract
Zea mays crop has been standing out in the Brazilian Cerrado of Piauí State, located in the Northeastern Brazil. However, despite the high technology level utilized, yield levels are still below the expectation, mainly due to the mismanagement of nitrogen (N). This experiment was conducted in field using single-cross hybrid 30F53 from Pioneer®. The experiment was conducted as completely randomized blocks design with nine treatments and four replications. The treatments consisted of five rates of N as urea, equivalent to 0, 60, 120, 180 and 240 kg N ha-1. It was applied twenty kg N ha-1 at sowing and the rest as topdressing. The splits comprised the application of 50% at the four expanded leaf stage (V1) + 50% at the eight expanded leaf stage (V2) or total rates at four expanded leaf stage. Leaf N content, leaf relative chlorophyll content, plant height, ear height, stem diameter, yield, grains per ear and rows per ear, grains per row, 1000 grains weight and agronomic efficiency index were measured. Nitrogen significantly increased agronomic characteristics of corn and the highest grain yield was obtained with 190.65 kg ha-1 N. Plant height, relative chlorophyll content, leaf N content, plant biomass, stem diameter, thousand seed weight, yield and agronomic efficiency index were positively influenced by the rates of nitrogen. The split of topdressing in twice was not suitable in the dystrophic Yellow Latosol of the Piauí Cerrado. Plant height, relative chlorophyll content, ear insertion height, stem diameter, grains per ear and rows per ear, grains per row and agronomic efficiency index positively correlated with grain yield. Key words: Agronomic efficiency index, yield, relative chlorophyll content.
Highlights
The Brazilian Cerrado of Piauí has been standing out in the national scenario with an extensive acreage favorable to grain Yuction, in particular for the corn and Glycine max crops
N is a nutrient absorbed in greatest amount, became it one of the greatest influence on yield, due to the several relevant functions in its physiological activities (Silva et al, 2005a, 2005c; Farinelli and Lemos, 2012) and the one which burdens the most on the Yuction cost of the crop
The experiment was conducted on the Fazenda União, municipality of Currais - PI (09° 37 '27 of "latitude and 44° 40' of 52" longitude and altitude of 541 m) in January-May 2012
Summary
The Brazilian Cerrado of Piauí has been standing out in the national scenario with an extensive acreage favorable to grain Yuction, in particular for the corn and Glycine max crops. 2,239 kg ha-1 (Conab, 2012) In this region, most soils present flat relief and excellent physical conditions for agricultural expansion (Pragana et al, 2012). Most soils present flat relief and excellent physical conditions for agricultural expansion (Pragana et al, 2012) They present low clay contents and low cation exchange capacity (CEC), mainly owing to low organic matter contents (OM), which for these soils. License 4.0 International License may stand for up to 80% of the CEC Owing to their low OM contents, they present low N supply capacity for corn. N is a nutrient absorbed in greatest amount, became it one of the greatest influence on yield, due to the several relevant functions in its physiological activities (Silva et al, 2005a, 2005c; Farinelli and Lemos, 2012) and the one which burdens the most on the Yuction cost of the crop
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