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

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 cm 3 cm −3 ensured the best results for all variables of commercial interest. No effect of potassium concentrations was observed on variables of commercial interest.