Comparative of Water Consumption Between Spray Irrigation and Drip Irrigation in a Lattuce Crop at Uruguaiana, Brazil

Considering the growing demand for drinking water faced by the planet currently, condition also verified on the agricultural production sector, the present article had the objective of dimension and evaluating two different models of irrigation commonly used in crops, in order to establish a comparison between the water consumption of each system. The models chosen for the study were the spray irrigation and the drip irrigation, the latter being proposed with two different layouts. The choice of these two models was due to their great spread in agriculture, considering that the first one has great possibilities of being replaced by the second one in the most varied types of planting. The simulation considered the municipality of Uruguaiana, located at south of Brazil, as well as the climatic and geological characteristics of the region. The study evaluated each of the irrigation methods over an area of ​​1,800 m², with the planting of cultivar Lactuca sativa L., popularly known as crisp lettuce. As methodological procedures, we emphasize the use of the irrigation methodology studied by Waldir Aparecido Marouelli, as well as the application of Hazen-Williams hydraulic calculations for the design of each system. It was also designed the subdivision of drip irrigation into two distinct layouts, each based on a different relationship between the number of plants and drippers. The results were wrote in electronic spreadsheets for comparative analysis. As a result, significant water savings were observed in the drip system when installing a single emitter per plant. This layout resulted in an eighty-two percent reduction in water consumption, relative to the spray irrigation model. The same level of water economy, however, did not occur when the sizing considered one emitter to each group of four plants, since in this case there was a water consumption only thirty percent smaller when compared to the spray irrigation. Thus, it is concluded that the water savings in the drip method is influenced by the layout used, and should therefore be one of the design constraints. Even though it is known that the costs of installing drip systems are higher than those used in spray irrigation, the reduction of water consumption in these systems is verified, and this reduction is even more significant when installing a single dripper per molt planted.