Adubação nitrogenada e potássica na severidade da antracnose em dois cultivares de milho

Abstract

The nutritional balance may contribute to increase plant disease resistance. With the aim of evaluating the interaction of nitrogen and potassium fertilization on severity of leaf anthracnose and mineral nutrition of maize, two experiments were installed in a greenhouse using two cultivars of corn, DAS 2B710 (moderately resistant to disease) and BRS 1010 (susceptible). Five doses of N (75, 150, 300, 600 and 1200 mg dm-3) and K (63, 125, 250, 500 and 1000 mg dm-3) were applied. The experimental design for each cultivar was completely randomized in a 5x5 factorial scheme, with 25 treatments and four replications. Each vase with four plants consisted of one experimental plot. The dosage of N and K were distributed in 4 applications at intervals of 10 days from sowing, for both cultivars. At 21 days after sowing, plants were inoculated and taken to a moist chamber with photoperiodic treatment of 16 hours in darkness for 3 consecutive days. After the inoculation, the severity was assessed daily for 11 days. At 43 days after sowing, the aerial part of the plant was harvested, dried and ground to determine the uptake of N and K. The severity was significantly affected by the interaction between nutrients. In both cultivars, the lowest severity values were observed at the lowest dose of N combined with the higher dose of K. The severity of the moderately resistant cultivar was 41% lower than in the susceptible cultivar. Nitrogen fertilization influenced negatively the K content in leaves and shoots.