Effects of early soil fertilization on the growth of Teak ( Tectona grandis ) in the Guinean Zone

Résumé fourni par la source

In response to climate change exacerbating tropical soil degradation and water stress, this study examines the importance of mineral fertilization for the productivity of teak (Tectona grandis) plantations. The main objective is to evaluate the effect of potassium fertilization on the growth parameters of the Indian provenance of teak in the Guinean zone (Zogbépimé station). The experiment was conducted on plots planted in 2018. The experimental design consisting of four plots, which were further structured into a total of eight sub-plots (four fertilized and four control) to capture within-plot variability. The treatment involved a manual application of 302 g of potassium chloride (KCl) per tree in 2020 and 2021. Dendrometric data, including diameter at breast height (DBH) and total height, were measured annually from 2020 to 2024 to compare the fertilized plots with the control plots.The results show that fertilization induced a progressive and cumulative positive effect, becoming statistically significant from 2021. In 2024, fertilized trees exhibited a diameter more than 10% greater (14.88 cm vs. 13.43 cm) and a total height 14% greater (16.71 m vs. 14.68 m) compared to the controls. Potassium efficacy peaked in 2023, with a maximum relative gain of 16.5% for diameter, before showing a slight decline in 2024 due to increased competition between trees and canopy closure. The study reveals that fertilization significantly weakened the natural allometric relationship between diameter and height; the coefficient of determination (R2) plummeted from 0.62 to 0.045 for treated trees by 2024, indicating a highly heterogeneous physiological response within the stand.In conclusion, the study confirms that potassium is a major limiting factor during the juvenile phase of teak in Togo. Regarding policy implications, these findings advocate for the integration of rational potassium fertilization protocols into national silvicultural guidelines, particularly for nutrient-deficient tropical soils, to enhance plantation profitability and mitigate economic losses from windthrow. To optimize wood production and plantation resilience, it is recommended to adopt an integrated management strategy combining rational potassium fertilization with early thinning operations. This research provides also a scientific basis for policy-driven genetic selection programs aimed at identifying genotypes highly responsive to potassium, thereby strengthening the forestry sector's resilience to climate variability.

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