Rendimento e avaliação nutricional do cultivo hidropônico de alface (Lactuca sativa L.) em sistema NFT no Semi-Árido brasileiro utilizando águas salobras

• Autor(a) principal: SANTOS, Alexandre Nascimento dos
• Data de Publicação: 2009
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: Biblioteca Digital de Teses e Dissertações da UFRPE
• Texto Completo: http://www.tede2.ufrpe.br:8080/tede2/handle/tede2/5558
• topic: Hidroponia; Salinidade da água; Irrigação; Alface; Lactuca sativa; CIENCIAS AGRARIAS::ENGENHARIA AGRICOLA

Ibimirim City in Pernambuco State is a municipal district located at the Brazilian semi arid and most of its wells produce brackish water. The use of this water has been avoided since it may cause human diseases and crop yield decrease. The objective of the present work was to evaluate the utilization of brackish groundwater and the reject from its desalination for hydroponic production of lettuce. Six levels of water salinity (CEa: 1.2; 2.2; 3.2; 4.2; 5.2 dS m-1) were analyzed in three experiments carried out inside a greenhouse. In the Experiment I, two salinity sources were evaluated: waters artificially salinized with NaCl and brackish groundwaters (AS), obtained from a deep tubular well and mixed with the reject of its desalination (reverse osmosis). Desalinized water was used to restore the evapotranspiration (ETc) losses. The increase of salinity by AS produced a negative effect on growth and yield of lettuce cv. Vera, with a reduction of 15.99 (dS m-1)-1 for fresh matter mass of shoot; there was no significant decrease of this variable using the source NaCl. Symptoms of generalized chlorosis were registered in plants submitted to salts from source AS. This result was attributed to nutritional disorders due the pH increasing in nutrient solution. The source AS produced lower leaf accumulation of Cu, Zn, Fe and Mn and higher accumulation of Ca and Mg. Experiment II was carried out with the same salinity levels of Experiment I using only brackish groundwaters for irrigation of two lettuce varieties (‘Vera’ and ‘AF1745’). These waters were used in overall production process (to prepare the nutrient solution and to restore the ETc). The salinity increase caused a linear reduction on lettuce plants growth. The plants exhibited general chlorosis at the beginning of the cycle, but this symptom was not verified at the harvest. The variety ‘Vera’ had a lower absolute growth and yield than the ‘AF-1743’. On the other hand, the percent reduction for both varieties was similar: the shoot fresh matteraccumulation was decreased in 17.06 and 15.74 % (dS m-1)-1 for ‘Vera’ and ‘AF-1743’, respectively. Leaf accumulation of N, P, Ca, Mg, Zn, Fe and Na was higher in variety ‘AF-1743’, while K accumulation was lower in this variety. The higher Na content in ‘AF-1743’ may explain the presence of burning of leaf edges of old leaves. In the Experiment III the utilization of brackish waters from five different wells was evaluated for production of the two lettuce varieties cited above. These waters were adjusted for the same salinity level (2.2 dS m-1) and were used to prepare nutrient solution and restore the ETc. The yield was not affected by the waters from the different wells; but the yield of ‘AF-1743’ was higher than ‘Vera’.