Effects on rice yield of two systems of irrigation: continuous flooding and soil saturation, in the "Baixada Fluminense"

Abstract

The yield responses of 12 rice cultivars to two different systems of irrigation were studied for three years on a hydromorphic soil of the "Guander" series located in Itaguaí, Rio de Janeiro. The systems of irrigation were: (1) continuous flooding; and (2) intermittent irrigation to the point of soil saturation. The first system is that commonly used by farmers in the area, but is more costly than the second system. The  experimental design was a split-plot, randomized complete block with four replications. Three-year averages revealed that continuous flooding yielded 187% more rough rice than the intermittent system, where the soil was saturated but not flooded. Yields, averaged over three years and all cultivars, were 2,395 and 831 kg/ha, respectively, for the two irrigation systems. All 12 cultivars yielded better under continuous flooding than intermittent irrigation. Under both irrigation systems highest yields were obtained with the "De Abril" cultivar, which had a three-year average yield of 3,222 kg/ha of rough rice. Economic analysis of yield data revealed that under continuous flooding only the "De Abril" cultivar yield was profitable and provided a return of Cr$ 371.84 per hectare. In comparison, the system of irrigating only to the point of soil saturation utilized an average of 98.5% less water and average profit obtained with the 12 cultivars was Cr$ 454.16 per hectare.