NITROGEN RATES AND SOWING SEASON INFLUENCE WHITE SPOT SEVERITY AND YIELD OF CORN

Abstract

The objective was to quantify the white spot severity in corn hybrids, under sowing times and nitrogen rates, and its correlation with relative chlorophyll content, thousand grain weight and yield. The design in sub-subdivided plots consisted of two hybrids AG9025 PRO3 (super early) and 30F53 VYH (early), preferential and late sowing, and nitrogen rates (0; 150; 300 and 450 kg ha^-1). The doses of nitrogen were applied in the V4, V8 and V12 stages in coverage. In VT stage chlorophyll reading was performed and in R6 quantification of severity using diagrammatic scale. AG9025 PRO3 showed an average severity of 17.7% in relation to 9.3% of the 30F53 VYH, demonstrating greater susceptibility. The preferential sowing time, with 2.2% of injured area, presents a lower severity compared to the late sowing season with 31.4%. There was a significant positive correlation between the severity and relative content of chlorophyll, a thousand grain weight and productivity, except for the 30F53 VYH hybrid in late sowing season. In the two sowing seasons, for the hybrid AG9025 PRO3 the severity of the white spot was increased with the highest nitrogen doses, and the effect of doses for the 30F53 VYH hybrid was not significant.