Growth and yield of cauliflower with brackish waters under hydroponic conditions

ABSTRACT Historically, and in the aggravating climate change scenario, droughts are increasingly severe in arid and semi-arid regions, limiting the use of irrigation. As an alternative for these regions, brackish waters have been used, despite the severe risks of soil salinization, as well as losses in crop production and quality. Thus, the adoption of adequate technologies should mitigate or control the impacts caused by salt stress. Therefore, in the present study two experiments were conducted to evaluate the cultivation of cauliflower with brackish waters using a nutrient film technique (NFT) hydroponic system from July to October 2019 (winter-spring) and from October 2019 to January 2020 (spring-summer). Cauliflower plants were subjected to six values of ECw: 0.3 - control (without NaCl), 1.5, 2.5, 3.5, 4.5, and 5.5 dS m-1 (with NaCl), in a randomized block design with six replicates. For the leaf blade area at inflorescence harvest, reductions per dS m-1 increment in ECw of 7.22 and 6.41% were found in the winter-spring and spring-summer experiments, respectively. The quality losses of cauliflower inflorescences were more pronounced in the spring-summer experiment, varying according to the ECw used. Therefore, it is possible to grow cauliflower hydroponically under ECw of up to 5.5 dS m-1; however, in the hottest seasons these waters should be reserved and used only for the preparation of nutrient solutions or replacement of water consumed by plants.摘要 从历史视角来看，在气候变化加剧的背景下，干旱半干旱区域的干旱灾害愈发严峻，灌溉用水的使用受到极大限制。对此类区域而言，咸水（brackish water）虽存在引发土壤盐渍化、降低作物产量与品质等严重风险，但仍被用作替代灌溉水源。因此，采用适配技术可缓解或管控盐胁迫带来的负面影响。本研究于2019年7月至10月（冬春季）、2019年10月至2020年1月（春夏季）开展两组试验，采用营养膜技术（nutrient film technique, NFT）水培系统，探究咸水栽培花椰菜的可行性。试验采用随机区组设计，设置6个营养液电导率（ECw）梯度：0.3 dS·m⁻¹为对照组（未添加NaCl），1.5、2.5、3.5、4.5、5.5 dS·m⁻¹为添加NaCl的处理组，每组设置6次重复。在花球收获期测定的叶面积数据显示，冬春季与春夏季试验中，ECw每提升1 dS·m⁻¹，叶面积分别降低7.22%与6.41%。花椰菜花球的品质损失在春夏季试验中更为显著，且随ECw梯度变化呈现差异。综上，可在ECw不超过5.5 dS·m⁻¹的条件下开展花椰菜水培种植；但在高温季节，这类咸水应仅用于配制营养液或补充作物耗水，不宜直接作为灌溉用水。