Study of the time of initiation of irrigation of five varieties of rice (Oryza sativa L.) in Baixada Fluminense

Abstract

The results of a comparison of five varieties of rice ("Amarelão", "De Abril", "Honduras", "7-V-8" and "H-12-V-13") in Baixada Fluminense in the State of Rio de Janeiro, Brazil are reported. The effect of beginning irrigation at the following stages of growth was compared: immediately after germination and at 10, 20, 30 and 40 days after germination. The system of irrigation employed was continous flooding. During the first four years (1960-61 to 1963-64) significant differences were encountered. The first, third and fourth treatments formed one group. The remaining treatments did not differ statistically from each other or from percentages of each group. During the final two years 1964-65 and 1965-66, treatments did not show significant differences. The interaction of variety X treatments was significant indicating that the variety "Amarelão" provided highest average yields when irrigation was initiated at 20 and 30 days after germination. The variety "Honduras" yielded more when irrigation was delayed until 30 days after germination. The variety "De Abril" had higher yields when irrigation started at germination. The two remaining  varieties (H-12-V-13 and 7-V-8) produced best when irrigation was delayed until 40 days after germination. Highly significant differences were also found among varieties. The best producer was "De Abril" with an average production for the first four years of 5,816 kg/ha and average of 3,855 kg/ha for the last two years. The yields of the other varieties were much lower. The first two treatments gave efficient control over weeds and grasses. The other three did not and at least one weeding was needed. These last treatments were more economical on the use of water. The reduced cost of securing this precious liquid was sufficient to offset the apparent advantage of the first two in reducing weed control cost.