Occurrence of rice blast on and grain quality of irrigated rice fertilized with nitrogen and silicates

Abstract

The objective of this work was to evaluate the effects of fertilization with nitrogen topdressing and silicates, as well as of the use of fungicides, on the occurrence of rice blast on panicles, milling yield, and whole grains, vitreous grains, and chalky kernels in a flood-irrigated rice cultivar sensitive to the disease. Two experiments were conducted in a randomized complete block design, in a 4x4x2 factorial arrangement, with four replicates: in experiment 1, four doses of nitrogen x four doses of calcium and magnesium silicate on soil x with and without fungicides; and, in experiment 2, four doses of nitrogen x four doses of potassium silicate applied on leaves x with and without fungicides. At the doses above 60 kg ha-1 nitrogen without fungicides, there was an increase of rice blast severity on panicles, a decrease in the percentage of whole and vitreous grains, and an increase in chalky kernels and chalky area. The greatest effects of silicates occurred without fungicides. Fungicide use reduced the severity of rice blast on panicles. Milling yield ranged from 60 to 70% in both experiments. The control of rice blast with fungicides maintains high rice grain quality, milling yield, and percentages of whole and vitreous grains.