Utilização do lisímetro de drenagem para obtenção do “KC” da mamoneira em plantio adensado

Abstract

Castor bean culture is considered resistant to water deficit. However, it presents considerable increase in productivity when submitted to irrigation. For the adequate irrigation management, one of the criterion considered is based on the crop evapotranspiration (ETc) and is necessary for finding the crop coefficient (Kc) value. With the present work, we aimed at determining the Kc of the castor bean in dense plantation, during the off-season, using a drainage lysimeter. Three drainage lysimeters, with dimensions of 1.2 m of length, 1.4 m of width and 1.2 m of depth, were used. In the lysimeters, eight castor bean seedlings, cultivar Al Guarany 2002 were planted with spacing of 0.3 m between plants and 0.7 m between lines. The ETc was calculated considering the interval from 5 to 12 days, according to the end of drainage. The reference evapotranspiration (ETo) was estimated by the Penman-Monteith-FAO equation. From the ETc/ETo relation, we obtained the Kc for the different periods over the crop cycle. The ETc values found in the initial, growing, intermediate and final phases were of 1.65; 3.07; 9.14 and 5.85 mm d-1, respectively. The Kc values for the mentioned phases were of 0.98; 1.41; 2.11 and 1.65, respectively.