Épocas de semeadura afetando índices morfofisiológicos de cultivares de arroz de terras altas

Abstract

The expression of the full yield potential of crops depends on genetic factors, favorable environmental conditions and management. This study aimed to determine the effects of sowing dates on the solar radiation use efficiency (RUE), on morphophysiological indices, and on the grain yield of contrasting upland rice cultivars. The field experiment was conducted in the central region of Brazil in soils in Cerrado areas. The experiment had a 3 x 5 factorial randomized design with eight replications. The treatments consisted of combinations of three cultivars (BRS Primavera, BRSMG Curinga, and Douradão) with five sowing dates (11/09/2012, 22/10/2012, 11/28/2012, 21/12/2012, and 27/2/2013). All cultivars required less accumulated degree-days to reach the reproductive phase as the sowing was delayed. The lower biomass accumulation and leaf area index (LAI) of the three cultivars occurred on the earlier sowing date, which may have been a result of lower RUE. The assimilate partitioning to leaves and stems was similar among cultivars, but the translocation rate of carbohydrates to the panicle was higher in the cultivars BRSMG Curinga and Douradão. The cultivars differed in the total number of grains per area, with the highest values found in Douradão and the lowest in BRS Primavera. The highest grain yields were obtained in sowing dates covering the traditional period of sowing upland rice, which is October to December.