Evapotranspiração e coeficiente de cultivo da mamona (Ricinus Communis l.), cv. brs energia, no Recôncavo da Bahia

Abstract

Castor bean has emerged as a crop of great potential for the Brazilian Northeast, making it necessary to pay attention in terms of determining its optimal cultivation needs in different places in the Region. Thus, it is imperative to know the evapotranspiration of castor bean under the climatic conditions of the Recôncavo of Bahia. For this, the lysimeter is used as a direct method of evapotranspiration determination. Therefore, we aimed to determine the evapotranspiration of the castor bean (Ricinus communis L.), cv. BRS Energia, and its crop coefficient, in the Recôncavo of Bahia conditions using lysimeters of drainage and constant water table. The experiment was conducted at the Experimental Farm of the Federal University of Recôncavo of Bahia, in an area of 816 m² with four lysimeters: two of them were lysimeters of drainage and other two of constant water table. The reference evapotranspiration (ET0) was estimated using the Penman-Monteith equation and the Class "A" pan. Biometric readings of growth and development variables were performed throughout the period. The crop coefficient (Kc) was calculated for the four stages of development: I - emergence of the plants up to the inflorescence of the first cluster; II - end of the preceding phase to the appearance of the inflorescence of the second cluster; III - end of phase II until the beginning of maturation of racemes; and IV - period between the beginning of maturation and the end of the cycle. Kc and leaf area index were related to day-degrees of development. At the end of the cycle, information on crop production and total water consumption was collected. The ETc measured by the constant water table lysimeter was 3.86; 4.45; 6.95 and 3.99 mm d-1 for phases I, II, III and IV, respectively, with a water consumption of 458.93 mm from the 30 days after planting until the end of the cycle. The evapotranspiration (ETc) values obtained by the drainage lysimeter were higher throughout the cycle than those measured by the water table lysimeter with an average discrepancy of 3.02 mm d-1. The lowest values of Kc were estimated by the relation between the ETc obtained by the water table lysimeter and the ET0 estimated by the Class A pan, and were 0.86; 1.06; 1.18 and 0.71 for phases I, II, III and IV, respectively.