CURVAS DE ENRAIZAMENTO DE MINIESTACAS DE CLONES DE EUCALIPTO

This study aimed to monitor the rooting process, fit rooting curves through mathematical modeling, and determine the optimal greenhouse retention time for mini-cuttings of six commercial eucalyptus clones to remain in a greenhouse, with the goal of optimizing the production of clonal seedlings in a commercial nursery located in Itamarandiba, Minas Gerais. The experiment was conducted using a randomized block design with six replicates and six hybrid eucalyptus clones: C1 (spontaneous Eucalyptus urophylla hybrid), C2 (E. camaldulensis × E. grandis × E. urophylla), C3 (E. camaldulensis × E. grandis × E. urophylla), C4 (E. pellita × E. urophylla), C5 (spontaneous E. urophylla hybrid) and C6 (Eucalyptus grandis W.Hill x Eucalyptus urophylla S.T Blake). Mini-cuttings were collected from a clonal mini-garden, planted in 50 cm³ containers with enriched substrate, and maintained under controlled temperature and humidity conditions. Data collection occurred every 3–4 days over 32 days, assessing the rooting percentage (roots > 1 cm). The data were fitted to the logistic model Y=α(1+βe−γT)−1+ε, which described the sigmoidal rooting behavior, enabling estimation of parameters α \alpha α (maximum rooting), β \beta β, and γ \gamma γ (rooting rate), with correlation coefficients ranging from 0.9705 to 0.9947. The optimal retention time was determined by the intercept method between the Daily Current Increment (DCI) and Daily Mean Increment (DMI) curves. Results revealed distinct rooting patterns among clones: C2 (14.8 days) and C6 (18.3 days) exhibited faster rooting, C1 (23.3 days) and C3 (22.1 days) showed intermediate behavior, while C4 (30.9 days) and C5 (29.4 days) displayed slower rooting. Maximum rooting ranged from 78.19% (C6) to 91,59 % (C4). These times closely aligned with those required to achieve 70% rooting (the company’s target), indicating the operational procedure’s suitability. The study proposed grouping the clones into three time classes to optimize greenhouse cycles: early (C2 and C6, 15–20 days), intermediate (C1 and C3, 20–25 days), and late (C4 and C5, 25–30 days). This approach could increase annual production by up to 2.1 million seedlings for early clones and 900,000 for intermediate clones, reducing costs and enhancing nursery efficiency. The study concluded that logistic modeling and tailored retention time adjustments are effective tools for maximizing eucalyptus clonal production, accounting for the genetic and physiological specificities of each clone.