Target spot is a disease that has caused serious damage to cotton crops. This study was carried out to examine if different cotton genotypes, plant heights and fungicide treatments can be used as tools of an integrated control methods of target spot. The experiment was carried out in the 2014/15 crop season, in cerrado biome of Chapadão do Sul -MS, Brazil. It was used a randomized block design in a 2 × 3 × 3 factorial arrangement with four replicates. The factors were two plant heights (1 and 1.5 m), three cultivars (FMT 701, FM 975, and FM 944), and three fungicide treatments (control, FT1, and FT2). Fungicide treatments consisted of sequential applications of different fungicides of the triazole, strobilurin, and carboxamide groups. Cultivar FM 944 showed lower susceptibility to target spot. The shorter plants exhibited lower disease severity.The fungicides pyraclostrobin + fl uxapyroxad and trifl oxystrobin + prothioconazole reduced the severity of target spot. Cultivar FM 975 had the highest yield. A higher yield was obtained in the upper stratum than in the lower stratum of the plant.
Most sandy soils have low natural fertility and low levels of organic matter, making nitrogen (N) fertilization essential. Thus, five doses of N were applied (0, 75, 125, 175 and 225mg dm-³) in a randomized block design to evaluate the effects of nitrogen fertilization on the morphogenetic, structural and production characteristics of Brachiaria brizantha cv. Marandu in a Quartzarenic neosoil. The doses of N did not affect the height of the canopy. The leaf elongation rate, final leaf length and number of live leaves increased linearly at the doses of N. Leaf appearance rate, stem elongation rate, leaf lifespan, phyllochron, leaf senescence rate and tiller density showed a quadratic response to the rates There was also an effect of N rates in herbage mass, leaf mass, stem mass, which increased linearly. Brachiaria brizantha cv. Marandu cultivated in Quartzarenic neosoil requires higher doses of N, 175 and 225mg dm-³. Under these conditions, increases in its morphogenetic, structural and productive characteristics are observed. These findings may not be repeated in the most fertile soils with the greatest capacity to supply N.
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