Consumo hídrico da mamoneira cultivar BRS energia irrigada com água salina no semiárido brasileiro.

Abstract

The castor-oil plant (Ricinus communis L.) is an oleaginous species which belongs to the Euphorbiaceae family. It is originated from Ethiopia and is normally cultivated under rain-fed conditions, which is relevant to the diversification of family agriculture and it is an important alternative to the progress of Brazil's northeast region. The experiment was conducted at Bahia's Federal Institute, inside the area for experiments on irrigation and drainage at the Senhor do Bonfim Campus. The objective of this work was to evaluate the water use in the castor-oil seed crop, BRS energy, irrigated with water containing different levels of salinity. The average crop cycle used was of 120 days, and the experiment began in September 2008 and ended in January 2009. The experimental design was composed of three repetitions, with a total of 21 experimental units. The reference evapotranspiration (ETo) was determined through the grass lysimeter method and the collected data were compared with the estimated data, through the Hargreaves-Samani empirical method. The crop evapotranspiration (ETc) was measured through the water balance method. It was also obtained to the BRS energy the crop coefficient (Kc), the production and the water efficient use. It was used the statistical software (STAT) for the data analysis and the treatment average were compared to the Turkey test with 5% of probability. The daily average values of the ETo which were measured during the cycle by means of the grass lysimeter, and estimated through the Hargreaves-Samani method, was 5.5 mm and 4.4 mm respectively. The average value of Kc, from the moment of sowing until the 79 DAE, was 1.11. It was observed that the total crop water consumption was gradually lowered according to the salinity levels used, and the largest reduction was identified in the water with a CEa of 4.8 dS m~'. The efficient use of water in the crop cycle was not altered on account of the fact that the amount of water used in the treatment was directly related to the crop efficiency itself. In other words, for the treatment in which a water supply (the witness) was used, the crop utilized a larger amount of water in order to yield more, since the plant showed a better growth and development when compared with the ones which were irrigated with water containing different levels of salinity, that is, they showed lesser growth and development, indicating low use of water.