Experiências de irrigação em cítrus, na Baixada Fluminense. I. Efeitos da irrigação sobre pomares de laranjas Piralima e Lima

Irrigation experiments were conducted beginning in the 1960/61 season in Piralima and Lima sweet orange orchards cultivated on Red Yellow Podzolic Soils of the Itaguai series, situated in the "Baixada Fluminense". The effects of irrigation pratices were studied during winter time. The water supplementation to the soil varied from 50 mm to 325 mm for each irrigation season. After four years of investigation with the Piralima variety (1960/61 to 1963/64), and six years with the Lima variety (1965/66 to 1970/71), it was observed that the irrigation at the 50 mm monthly level was the one that presented the best results for the first variety, resulting in an average increase of 37 fruits per tree during four years. Concerning the Lima sweet orange, without chemical fertilization and irrigated at the different water levels, there were no significant differences in the 1965/66 and 1966/67 seasons. However, in the 1965/66 season, irrigation at the 50 mm water level resulted in an increase of 139 fruits over the controle and 78 fruits over the 25 mm monthly water supplementation. In the 1967/68 and 1968/69 seasons the association of a uniform chemical fertilization (NPK 8-4-8) of 2 kg per tree at the monthly level of 50 mm resulted in a significant increase of 136 fruits over the controle, for the agricultural year of 1967/68. There was no reaction to the double and quadruple chemical fertilization concerning fruit production and its pomological qualities, and no correlation between the different water levels in the 1969/70 and 1970/71 seasons.