Fertilização nitrogenada como ferramenta para mitigação de efeitos do déficit de radiação solar no arroz irrigado
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2023-09-06
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Universidade Federal de Goiás
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Rice is part of the routine diet of the Brazilian population. Worldwide, it is considered one of the species with the greatest potential for combating hunger. Nitrogen is the nutrient most required by the rice crop. Solar radiation is one of the elements of the climate that most affects crop productivity. In Brazil, rice is grown in different regions, whose locations have a different supply of solar radiation throughout the cycle. This is one of the factors that explains the differences in productivity between regions. Some studies have shown that the supply of nitrogen as a top dressing minimizes the damage caused by solar radiation deficit in irrigated rice. In view of the above, the aim of this study was to determine the impact of the solar radiation deficit on two cultivars of irrigated rice and to investigate whether the supply of nitrogen minimizes the effects caused by this deficit. Two field trials were conducted for the 2019/2020 and 2020/2021 harvests. The work was carried out at the Palmital Farm experimental station, belonging to Embrapa Rice & Beans, in the municipality of Goianira-Goiás. The experimental design was randomized blocks, with four replications. The treatments were arranged in a subdivided plot design, with shading as the main plot, the nitrogen dose as the subplot and the cultivars as the sub-sub-plots. The cultivars studied were BRS Catiana and IRGA 424 RI. The nitrogen source used was urea, at doses of 50 kg ha-1 of N (applied just once, at the V2 stage) and 180 kg ha-1 of N (spread over three seasons, V2; V3 and V6, with the respective doses of 50; 50 and 80
kg ha-1 of N). The light-restricted plots were covered with a black propylene screen with an attenuation capacity of 30% of global solar radiation, which was installed at the start of flowering (R4) and remained in place until physiological maturity (R9). Fifteen days after the shading was installed, the plants' gas exchange was assessed using an infrared gas analyzer. At the same time, plant samples were taken for analysis of non-structural carbohydrates (NSC) and total nitrogen content. At harvest time, a 1.0 m row was sampled for analysis of yield components. Yield was obtained by harvesting 10 m of the row. Whole grain yield was assessed by processing a 100 gram sample from each experimental plot. The data was submitted to analysis of variance and the means were compared using the Tukey test (p<0,05). Shading reduced the concentration of non-structural carbohydrates in the leaf and stem of the cultivars in the shaded condition. The nitrogen content in the plant was reduced under conditions of light restriction. Gas exchange (net photosynthesis, stomatal conductance, internal CO2 concentration and transpiration) was affected by the availability of solar radiation. Under shaded conditions, there was a lower yield of whole grains. Increased nitrogen application allowed for a recovery in gas exchange, non-structural carbohydrates, nitrogen content in the plant, productivity and whole grain yield, under conditions of limited solar radiation. The IRGA 424 RI cultivar had a greater ability to adjust in the shaded condition compared to BRS Catiana, which implied higher productivity in this condition. In the unshaded condition and at the highest dose of N (180 kg ha-1), the BRS Catiana cultivar showed higher productivity than IRGA 424 RI. Applying nitrogen as a top dressing is a management strategy that can be applied to minimize the impact of solar radiation deficit on irrigated rice crops.
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MARQUES, R. C. Fertilização nitrogenada como ferramenta para mitigação de efeitos do déficit de radiação solar no arroz irrigado. 2023. 75 f. Tese (Doutorado em Agronomia) - Escola de Agronomia, Universidade Federal de Goiás, Goiânia, 2023.