Necessidades hídricas e produtividade de água da cultura do meloeiro irrigado na região de Mossoró-RN.

Abstract

Currently, melon is the second most important fruit in Brazilian exports, and the state of Rio Grande do Norte is the largest producer in Brazil, with 41% of the total planted area. The melon is cultivated in this region using plastic cover (mulch) on the ground and depends on groundwater irrigation. With the growing demand for food, agricultural water use in semiarid regions should consider applying the least amount of water that can ensure good yields and soil conservation. The objective of this study is to determine the water needs and water productivity of irrigated melon cultivated with mulch in the semiarid region of Rio Grande do Norte. For this purpose we used the Bowen Ration Energy Balance (BREB) method and the Surface Energy Balance Algorithm for Land (SEBAL) to determine crop coefficients (Kc) and evapotranspiration of melon crops in four farms in the municipality of Mossoró (Dinamarca: 4º54’28” S; 37º24’06” W; 17 m, Brazil Melon: 4º54’26” S; 37º23’02” W; 29 m, Fruta Vida: 4°59’52” S; 37°23’09” W; 54 m e Norfruit: 4º54’10” S; 37º22’01” O; 36 m). The BREB field experiment was carried out twice in the 2009/2010 season. Five Landsat Thematic Mapper-5 images were processed to determine evapotranspiration by SEBAL. Indicators of productivity and water use were applied to data collected in the field and generated by SEBAL. The average Kc determined in two field experiments was 0.26, 0.96 and 0.63 for initial, middle and end stages, respectively. The values estimated by SEBAL were close to those found by BREB with a maximum deviation of 16% between the methods. Productivity and water use indicators varied widely in the studied area. The relative water supply for the crop was satisfactory, however the average deplect fraction was 0.61, revealing that 39% of applied water was not used by plants. The average crop water productivity based on irrigation was 6.47 kg m-3. The economic analysis of water productivity revealed high values to melon, with an average of 4.41 US $ m-3.