Evapotranspiração e rendimento de cultivos solteiro e consorciado de milho e amendoim sob diferentes lâminas de irrigação

Abstract

An experiment was carried at the School of Agronomy Experimental Station of the Federal University of Bahia, at Cruz das Almas, aiming at evaluating the water use and yield of green maize and groundnut, using the field water balance technique and a line-source sprinkler system to irrigate the area. The experiment followed a split-block design with two cropping systems (mono and intercropping) e four irrigation levels (L1, L2, L3, and L4, respectively 125, 100, 60, and 25% of reference ET from a Classe A pan). Reference ET was obtainded by the Hargreaves, Class A pan and FAO Penman-Monteith methods. Maximum ET for sole maize, sole groundnut and intercropping was 6.3; 5.2 and 7.2 mm day-1, respectively. For sole maize, Kc varied from 0.81 to 1.29; for sole groundnut, it varied from 0.68 to 1.07 and for intercropped maize-groundnut, Kc varied from 1.12 to 1.35. No significant difference for green maize yield was found between cropping systems (sole – 4925.78 kg ha-1 and intercropping – 5341.68 kg ha-1). There was interaction between cropping systems and irrigation level. The highest sole maize yield (6765.62 kg ha-1) was obtained with the L3 level followed by the L2 level with 6593.75 kg ha-1, without statistical difference between them. In the intercropping systems, the L1 level promoted the highest maize yield (8151.44 kg ha-1) followed, with no significant difference, by the L2 level with 7819.44 kg ha-1. But, both L1 and L2 levels differed significantly from L3 and L4 irrigation levels. For groundnut, statistical difference was observed in terms of air dried pod yield between crop systems (sole – 4013.12 kg ha-1 and intercropping – 1970.62 kg ha-1). No interaction was observed between cropping systems and irrigation levels. The yield of air dried pods did not differed statistically among irrigation levels, exception for the L4 for which yield was the lowest (1816.87 kg ha-1). Maize and groundnut are two important crops for small farmers in the Recôncavo Baiano region where demand for both green maize and groundnut is high mainly in the first half of the year. The crops are commonly planted as sole cropping systems but the potential for intercropping is also high. The growing season extends from March to June when the rain amount and distribution is enough to supply crop water needs. After that, the lack of rainfall lowers the planted area so that irrigation can be an alternative to stabilize the production in the dry period. To assess maize and groundnut evapotranspiration and to derive crop coefficients for irrigation scheduling, a field work was carried out at the School of Agronomy Experimental Station of the Federal University of Bahia. Sole cropping and intercropping systems of maize and groundnut were established under sprinkler irrigation, from October 2003 to January 2004. The field water balance technique was used to evaluate crop water consumption. The irrigation depth was based on daily measurements of evaporated water from a Class A pan. Reference ET was calculated using the Hargreaves, Class A pan and FAOPenman-Monteith methods. Maximum ET rate for maize sole cropping, groundnut sole cropping and intercropping was 6.3; 5.2 and 7.2 mm day-1, respectively. For sole cropped maize, Kc varied from 0.81 to 1.29; for sole cropped groundnut, it varied from 0.68 to 1.07 and for the intercropped maize-groundnut system, crop coefficient varied from 1.12 to 1.35.