Manejo de fungicidas e nitrogênio em trigo e seus efeitos na produtividade e qualidade de grãos

Abstract

The wheat crop is severely attacked by diseases, which significantly reduce its profitability. The diseases reduce not only productivity but also quality, factor that is essential for the actual economic culture viability. In order to analyze which factors regarding chemical control of foliar diseases are essential to allow bread wheat varieties express the trait, this thesis sought to clarify the interaction between varieties and fungicides in better utilization of nitrogen and its implications for productivity and quality of wheat grains. The two experiments were arranged in a factorial split-plot design in randomized blocks with six replications. The results showed that the fungicides, especially strobilurins, promoted better use of nitrogen in wheat plants. The interactions between the effects provided by fungicides in disease control, and its direct effects on wheat plants physiology, were decisive factors for obtaining high-quality wheat for bread production. The data showed that the increase in nitrogen availability significantly increased the gluten strength. Showing also that, the diseases have committed the remobilization of nitrogen from leaves to grains. Differences were evident between strobilurin and triazole fungicides to control leaf spot and leaf rust, where the epoxiconazole were more effective in the leaf spot complex control, compared to strobilurins. The growth stages of elongation and emission of spikes were critical times for the chemical control of leaf spot. The use of nitrogen in the vegetative stage of wheat increased productivity and its use in the reproductive stages increased the gluten strength. The pyraclostrobin fungicide applied since the seed treatment provided a higher yield and gluten strength.