Chicory (Cichorium intybus L.) yield under water stress and estimation of leaf area using allometric relations

Abstract

Leafy vegetables are mainly grown in small properties using empirical irrigation control and frequently applying excess water. Considering these aspects, this study aimed at (i) evaluating the chicory (Cichorium intybus L. cv. "Folha Larga") production, grown in a greenhouse under different irrigation levels, proportional to the reference evapotranspiration (ET0) and (ii) adjusting models to estimate chicory leaf area from leaf linear measurements. For this, the chicory was grown in a 120 m2 greenhouse. A completely randomized experimental design was used, applying five irrigation treatments and nine repetitions per treatment. The irrigation treatments consisted of percentages of ET0, as follows: 45.6; 60.8; 76; 91.2 and 106.4% of ET0. Measurements of plant height, number of leaves, shoot fresh and dry mass and leaf area were taken. Measurements of 605 leaves were used to adjust ten initial models, from which four models were selected based on statistical coefficients. These models were then submitted to statistical analysis to obtain models which residuals present tendency to normality and homoscedasticity. Measures of 250 new leaves were used to apply the Bland-Altman graphical method. The results show that the increase in one percent of ET0 applied by irrigation increased the plants height in 0.148 cm, and 0.263 and 0.0158 g in the shoots' fresh and dry mass (respectively) and decrease in 0.306 cm 2 of the leaf area. Bland-Altman method revealed that the models estimated correlated but non-concordant data, pointing out to the need of adding the biases' value of each model to the estimated values.