WATER REQUIREMENT AND CROP COEFFICIENT OF MAIZE AND COWPEA IN SOLE AND INTERCROPPING SYSTEMS

ABSTRACT:

In order to determine the water requirement and crop coefficient for the different phenological stages on corn plants ( Zea mays L.) and cowpea plants ( Vigna unguiculata (L.) Walp) in intercropping and sole cropping systems under the climatic conditions of the Brazilian semiarid. The experiment was conducted in the city of Petrolina, PE. Shoots total dry mass and photosynthetically active radiation intercepted for both crops were monitored. Furthermore, it was obtained the evapotranspiration (ETc) by the soil water balance method. With these data and reference evapotranspiration it was obtained crop coefficient (Kc), which were subsequently used to adjust models as a function of accumulated degree days. With the results, it was found the water requirements from maize and cowpea intercropped system were greater than the sole system. Kc in the intercropped system was 0.90, 1.30, 1.20 and 0.72 for maize and 0.86, 1.30, 1.21 and 0.91 for cowpea, respectively, for the vegetative, flowering, grain filling and ripening stages. In the sole system, these values were, 0.86, 1.23, 0.97 and 0.52 for maize and 0.68, 1.02, 1.06 and 0.63 for cowpea in those phases mentioned. The variations of the Kc values for both systems and cultures have been associated to the increase of biomass and light interception. The Gaussian model adjusted properly described the relationship between Kc and accumulated degree days.

Keywords:
Crop coefficient; Water demand; Soil water balance; Irrigation; Intercropping.