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 长期以来，在气候变化加剧的背景下，干旱与半干旱地区的干旱灾害愈发严峻，大幅限制了灌溉用水的可及性。咸水虽存在引发土壤盐渍化、降低作物产量与品质的显著风险，仍被作为上述区域的替代水源加以利用。因此，需采用适配性技术以缓解或管控盐胁迫带来的负面影响。为此，本研究开展两项水培栽培试验，于2019年7月至10月（冬春季）、2019年10月至2020年1月（春夏季）采用营养液膜技术（Nutrient Film Technique, NFT）水培系统种植花椰菜，以咸水作为灌溉水源。试验设置6个灌溉水电导率（electrical conductivity of irrigation water, ECw）梯度：0.3 dS·m⁻¹（对照组，未添加NaCl）、1.5、2.5、3.5、4.5及5.5 dS·m⁻¹（均添加NaCl），采用随机区组设计，设置6次重复。花序采收期的叶面积测定结果显示，冬春季与春夏季试验中，灌溉水电导率每提升1 dS·m⁻¹，叶面积分别下降7.22%与6.41%。花椰菜花序的品质损失在春夏季试验中更为显著，且随灌溉水电导率的变化而有所差异。综上，可在灌溉水电导率最高达5.5 dS·m⁻¹的条件下开展花椰菜水培种植，但在高温季节，咸水应仅用于配制营养液或补充植株耗水。