Abstract
ABSTRACT Rice phenology and development are events controlled by environmental and genetic factors, and the yield potential of the crop is defined by their interaction. This study aimed at analyzing the performance of irrigated rice genotypes in contrasting ecosystems and their effects on morphophysiological characteristics. Two ecosystems (tropical and subtropical) were analyzed, as well as cultivars recommended for tropical (BRS Catiana and BRS Jaçanã) and subtropical (BRS Pampa, BRS 7 Taim and IRGA 424) regions. The experiments were arranged in a complete randomized block design, with four replicates, being the factors the genotypes, sowing times and sites. The phenological development, biomass dynamics, radiation use efficiency and grain yield were evaluated. The accumulated degree-days demand for flowering decreased faster in the tropical ecosystem than in the subtropical ecosystem for late sowing. The radiation use efficiency values were similar in the subtropical ecosystem and yield was high for all sowing dates. On the other hand, the tropical ecosystem showed a high variation for radiation use efficiency values and yield. The higher accumulation of degree-days and solar radiation during the reproductive and grain-filling phases contributed to increase yield in both ecosystems.
Highlights
Rice (Oryza sativa) is the second most cultivated cereal crop in the world and it provides 21 % of the energy and 15 % of the protein consumed by humans (Zibaee 2013)
In Goianira (Figure 1a), advancing the sowing time increased the demand for accumulated degreedays (ADD) to reach V6, especially in September, what was not recorded in Cachoeirinha (Figure 1b)
The opposite occurred in the grain-filling phase, with a higher rate in Goianira, what explains the equivalence of the cultivar cycle time in both environments, which was 128 days
Summary
Rice (Oryza sativa) is the second most cultivated cereal crop in the world and it provides 21 % of the energy and 15 % of the protein consumed by humans (Zibaee 2013) It is cultivated in different ecosystems, from the humid tropics to the temperate zone, and the impact of this climatic variability differs regionally (Wassmann et al 2009). Rice is cultivated in southern Brazil, accounting for 70 % of the domestic production, with an average yield of 7 Mg ha-1. In the tropical region, irrigated rice is produced mainly in the states of Goiás, Tocantins, Mato Grosso do Sul, Maranhão, Ceará, Pernambuco, Sergipe and Alagoas, and accounts for only 10 % of the domestic production, with an average yield of 5 Mg ha-1 (Nascente & Santos 2016). The diversification of the agricultural matrix of the aforementioned states is important
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