MOISTURE LIMITS AND POTASSIUM CONCENTRATIONS IN THE SOIL SOLUTION FOR CULTIVATION OF LISIANTHUS (Eustoma grandiflorum) FERTIGATED UNDER PROTECTED ENVIRONMENT CONDITIONS

ABSTRACT Lisianthus (Eustoma grandiflorum) has been attracting great interest due to the beauty of the colors of flowers, the firmness of stems, and postharvest durability. However, knowledge of lisianthus irrigation and fertigation has generally been based on recommendations from other countries. This study aimed to establish parameters for the rational management of lisianthus fertigation under a protected environment by determining the best lower limit of soil moisture, associated with the determination of the optimal potassium concentration to be maintained in the soil solution. The treatments consisted of five soil moisture limits for the start of irrigation and maintenance of five potassium concentrations in the soil solution, with four replications. Plots of 0.7 by 0.5 m were arranged in a completely randomized block design in a factorial scheme. The soil solution was monitored by measuring moisture as well as potassium (K+) concentrations using a TDR100 reflectometer and solution extractors, respectively, during two cycles. The evaluated variables were the leaf area index, shoot fresh and dry matter, commercial yield, and average stem diameter. Lisianthus cultivation under the lower limit of soil moisture equal to 0.20 cm3 cm−3 ensured the best results for all variables of commercial interest. No effect of potassium concentrations was observed on variables of commercial interest.

摘要 洋桔梗（Eustoma grandiflorum）凭借花色素雅美观、茎秆坚韧挺拔以及采后贮藏耐久性佳的优势，受到广泛关注。然而，当前针对洋桔梗灌溉与水肥一体化施肥的相关技术认知，大多基于其他国家的推广建议。本研究旨在明确设施保护地栽培环境下洋桔梗合理化水肥管理的核心参数，具体通过确定最优土壤水分下限，同时明确土壤溶液中适宜的钾素浓度来实现该目标。试验设置5个灌溉启动阈值对应的土壤水分下限梯度，以及5个土壤溶液钾素浓度梯度，每组处理设置4次重复。试验小区规格为0.7 m×0.5 m，采用析因设计的完全随机区组方案进行布置。在两个种植周期内，分别采用TDR100反射仪（TDR100 reflectometer）与土壤溶液提取器，对土壤水分及钾离子（K+）浓度进行监测。本研究测定的指标包括叶面积指数、地上部鲜重与干重、商品产量以及平均茎粗。结果表明，当土壤水分下限设置为0.20 cm³·cm⁻³时，所有具有商业应用价值的测定指标均表现最优；而钾素浓度对各类商业性状指标无显著影响。