The rising demand for lumber and other forest products has heightened the significance of short rotation, intensively managed planted forests globally in recent times. Although teak ( Tectona grandis ) plantations are perhaps the most significant wood resources in the tropics, relatively few studies on teak fertilization have been conducted, typically with contradictory results. This study examined the effects of NPK fertilizer rates on the survival and growth performance of teak within the first 5 years of establishment. Four levels of NPK fertilizer were applied in teak plantations in a completely randomized block design. Survival and growth were monitored over 5 years. Mixed models with repeated measures were applied to model survival and growth of the trees. The unstructured covariance structure better‐fitted the survival and growth (diameter, height, basal area and volume) data with −2 loglikelihood scores significantly lower ( p < 0.001) than all other models. Based on the fitted model, the effects of the fertilizer treatment, time and blocking were significant ( p < 0.05) for survival, height, DBH, stand basal area and stand volume. The fertilizer–time interaction effects were significant for only survival ( p = 0.0002) and stand volume ( p = 0.0061). The survival was about 86% in the control treatments and 94%–97% in the fertilizer treated plots, four years after establishment. Overall, all growth parameters increased significantly with time. However, the most dramatic changes were observed between Years 4 and 5 due to the thinning introduced at the end of Year 4. The DBH increased from 0.53 ± 0.3 cm in the first year to 10.00 ± 0.22 cm in the fifth year. The total height of the trees also increased at a rate of 1.53 m per annum from 1.02 ± 0.07 m in the first year to 7.65 ± 0.14 m in the fifth year. Fertilizer application resulted in marginally higher total height, DBH, stand basal area and volume growth than the control for each of the 5 years after establishment. Mean annual increment (MAI) in DBH and total height after thinning were roughly 2.0 and 2.5 times higher than the MAI before thinning, and these differences were significant among treatments ( p < 0.001). The study concludes that the lack of fertilizer effects on teak growth performance in these early stages may be attributed to adequate inherent soil fertility and are likely transient since demand for nutrients might increase later in the stand rotation. Further monitoring of these trial plots for the entire rotation cycle is required for more informed inferences regarding these treatments.
Nero et al. (Wed,) studied this question.