Improving growth of shea butter tree (Vitellaria paradoxa C.F. Gaert.) seedlings using mineral N, P and arbuscular mycorrhizal (AM) fungi

For the successful cultivation of most undomesticated fruit trees such as shea butter tree (Vitellaria paradoxa C.F.Gaertn.), there is a need to identify their nutrient requirements and optimal growth conditions. Responses of shea seedlings to combined N and P fertilization, and to inoculation with arbuscular mycorrhizal (AM) fungi was investigated. Six months old shea seedlings were transplanted into pots and grown for six months using a sterile nutrient-deficient soil. The seedlings were inoculated with the AM fungus Glomus intraradices Schenk & Smith. The fertilization treatments consisted of a factorial combination of three levels of N supplied as NH4NO3-N and P supplied as Ca(H2PO4)(2). Fertilization stimulated plant height, collar diameter and dry weights (DWs) compared with non-fertilized treatments, These improvements were associated with in increase in total shoot N and C uptake (33% increase) whereas P and K contents were not affected. There was significant N x P interaction oil DWs and total shoot N and C contents, suggesting that seedling N responses were influenced by P rates. Consistent N responses in DWs, and total shoot N and C uptake were significant at the lowest P rate. P increases promoted growth and total Shoot nutrient contents in low N-treated seedlings, while reducing growth in higher N rates. The combined application of medium and high rates of N and P fertilizers showed relatively low impact oil seedling growth presumably because of suboptimal N:P ratios. Mycorrhizal root colonization was generally low 12%) and was not affected by any of the treatments. There was also no response to inoculation with AM fungi probably because the established mycorrhizal association was ineffective. The potential use of both mineral fertilizers and AM fungi to promote growth performance of shea seedlings are discussed.

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