Macronutrient cycling in hydroponic lettuce cultivation

Abstract In order to address issues of limited resources and contamination by fertilizers, nutrient solutions may be reused in hydroponics as an alternative to their disposal in the environment. This work evaluated the feasibility of nutrient replacement for the nutrient solutions reused during lettuce hydroponic cultivation. The experiment was carried out in an agricultural greenhouse in an NFT hydroponic system using the “Milena” lettuce cultivar. The experiment was divided into two stages: 1) monitoring and data collection and proposition of nutrient replacement management; and 2) validation of the proposed replacement management. Monitoring the consumption of the crop's nutritional solution in the first stage served as the basis for the proposed nutritional replacement management. Management was validated in the second stage through the evaluation of fresh and dry mass, crop nutritional status, and the amount of the fertilizer applied in the treatments: T1 - nutrient replacement with nutrient solution reuse; and T2 - nutrient replacement without nutrient solution reuse. The fresh and dry mass data and the amount of nutrients absorbed by the plants were submitted to the t-test at 5% probability, showing no significant difference between the treatments, making it possible to conclude that the nutrient solution reuse provided nutrient replacement during the lettuce crop cultivation.摘要 为解决水培营养液资源有限及化肥污染问题，可将营养液回收复用替代直接排放至环境。本研究评估了生菜水培种植中复用营养液的养分补充可行性。实验于农业温室中开展，采用营养液膜技术（NFT）水培系统，种植品种为“Milena”生菜。实验分为两个阶段：1）监测与数据采集，并提出养分补充管理方案；2）对所提补充管理方案进行验证。第一阶段通过监测作物营养液消耗量，为养分补充管理方案的制定提供依据。第二阶段通过测定鲜重、干重、作物营养状况以及各处理组化肥施用量对该管理方案进行验证，两组处理分别为：T1组采用营养液复用+养分补充方案，T2组采用营养液不复用+养分补充方案。对植株鲜重、干重及养分吸收量数据进行5%显著性水平下的t检验，结果显示两组间无显著差异，由此可得出结论：生菜种植过程中，营养液复用可实现养分补充。