MINERAL NUTRITION OF CRISPHEAD LETTUCE GROWN IN A HYDROPONIC SYSTEM WITH BRACKISH WATER

ABSTRACT Water availability in the Brazilian semiarid is restricted and often the only water source available has high salt concentrations. Hydroponics allows using these waters for production of various crops, including vegetables, however, the water salinity can cause nutritional disorders. Thus, two experiments were conducted in a greenhouse at the Department of Agricultural Engineering of the Federal Rural University of Pernambuco, to evaluate the effects of salinity on the mineral nutrition of crisphead lettuce, cultivar Taina, in a hydroponic system (Nutrient Film Technique), using brackish water in the nutrient solution, which was prepared by adding NaCl to the local water (0.2 dS m-1). A randomized blocks experimental design was used in both experiments. The treatments consisted of water of different salinity levels (0.2, 1.2, 2.2, 3.2, 4.2 and 5.2 dS m-1) with four replications, totaling 24 plots for each experiment. The water added to compensate for the water - depth loss due to evapotranspiration (WCET) was the brackish water of each treatment in Experiment I and the local water without modifications in Experiment II. The increase in the salinity of the water used for the nutrient solution preparation reduced the foliar phosphorus and potassium contents and increased the chloride and sodium contents, regardless of the WCET. Foliar nitrogen, calcium, magnesium and sulfur contents were not affected by increasing the water salinity used for the nutrient solution preparation.

摘要：巴西半干旱地区水资源可利用性受限，且多数情况下唯一可用水源的盐浓度偏高。水培技术可利用此类水体种植包括蔬菜在内的多种作物，但水体盐度过高可能引发作物营养失调。为此，研究团队在伯南布哥联邦农村大学农业工程系的温室中开展两项试验，以评估盐度对采用营养膜技术（Nutrient Film Technique）的水培系统中脆叶生菜（品种：泰纳，Taina）矿质营养的影响；试验所用营养液为由当地水源（电导率0.2 dS·m⁻¹）添加氯化钠配制的咸水。两项试验均采用随机区组实验设计。处理组设置了6个盐度水平的水体（0.2、1.2、2.2、3.2、4.2及5.2 dS·m⁻¹），每组设置4次重复，每项试验总计24个试验小区。用于补偿蒸发蒸腾所致水量损失的补水（WCET），在试验I中采用对应处理的咸水，试验II中则使用未作改性处理的当地水源。无论采用何种补水方式，用于配制营养液的水体盐度升高均会降低生菜叶片的磷、钾含量，同时提升叶片氯、钠含量；而生菜叶片的氮、钙、镁及硫含量则不受营养液配制用水盐度升高的影响。