Avaliação das necessidades hídricas e manejo de irrigação da cultura de amendoim.

Abstract

The use of irrigation in the Brazilian Northeast region has been increasing, what requires, as an advise the acknowledge of crops water requirements. So that, it was conducted a field experiment with a new peanut cultivar, the BR1, during the 1996 growing season, in Rodelas-Ba. The research had the objective of identifing the evapotranspiration estimation method most appropriated to the peanut cropping conditions, as well as to determine the crop water requirements for its whole growing cycle and to provide allowance to the its irrigation efficiency. A micrometeorological tower was installed in the center of a 2ha peanut growing area with measurements of the instantaneous environmental parameters been taken by a data logger system. The crop water consumption was daily measured by two constant water table evapotranspirometers. The maximum evapotranspiration daily value it was 11 mm/day in the seed maturity phenological phase, reaching 632,2mm in the whole growing cycle. The soil available water affected in about 30% the plants growth of the field, in comparison with the plants of the evapotranspirometers. The daily change of the environmental parameters showed a frequent occurrence of hot and dry air advection, always associated to strong winds. The model for estimating the evapotranspiration showed a tendency for overestimating ET in the initial crop growing phase and underestimating in the final phase. According to the statistical analysis, the Penman-Monteith method presented the best adjustment to the observed data (r^Q.74), getting better with the use of crop variables more representatives of the daily period. Despite the good adjustment of the Class "A" pan method (^=0.89), used for estimating the reference evapotranspitation, the Penman-Monteith-FAO method showed more consistenty values. Due to environmental conditions the obtained kc values were higher than those of the literature and showed a subdivision in the flowering phase. The irrigation of the peanut crop growng in the region of Rodelas-Ba shoud be applied in the early morning with the water amount been established as a function of the irrigation system efficiency and based on the crop coefficient obtained by the Penman-Monteith-FAO method.