Taproot pruning in nursery is an efficient method to improve Vitellaria paradoxa seedlings growth and survival

Abstract

The shea tree (Vitellaria paradoxa C. F. Gaertn.) is an ecologically and socioeconomically important species in both forest and agroforestry systems. Still, its root system, added to slow seedling growth, challenges seedling production in nursery, causing a loss of interest in planting. In this study, we assessed the impact of taproot pruning on seedling growth and survival in nursery. Seeds that were collected from agroforestry systems and savannas in Benin were sown in plastic bags filled with forestry soil. One year after seed germination, the taproot of the seedlings was pruned at varied intensities: 1/3 taproot pruned (OTTP); 1/2 taproot pruned (HTP); 2/3 taproot pruned (TTTP); unpruned seedlings on ground (NOTP); unpruned seedlings on a sturdy mat (NOTP_OC). The results showed that taproot pruning positively impacted both seedling growth and survival, with TTTP and OTTP showing the highest growth rates. The 6-month and 11-month probabilities of survival were 95.7% and 67.5%, respectively, indicating an increasing mortality over time, especially for NOTP_OC and OTTP. However, TTTP did not present any risk of mortality, while HTP treatment had a significantly lower risk of mortality. Therefore, TTTP treatment can be recommended for the management of the root system of V. paradoxa seedlings. Our research should be useful for foresters and nursery keepers, especially the producers of shea seedlings. Further investigations of taproot-pruned seedling responses to severe water and nutrient constraints, as well as tree stability to wind storms after planting in forest stands or agroforestry systems, are needed.