Gum arabic production in Acacia Senegal plantations in the Sudanian zone of Cameroon: Effects of climate, soil, tapping date and tree provenance

摘要

This study was conducted in the Sudan-ian zone of Cameroon, where annual rainfall ranges from 650 to 1,250 mm, to assess the growth of Acacia Senegal (L.) Willd. and evaluate the influence of tapping dates, as well as climatic and edaphic effects on gum arabic production. The tree plantations were established between 1985 and 1989, and the tapping tests were carried out between 1993 and 1998. Generally good adaptation and growth of the species were observed in the different site conditions of the study area. To optimize gum production, the best time to tap the trees was at the beginning of the dry season, when the relative humidity dropped. Depending on the location along the climatic gradient, the optimum tapping date varied from October 10th (650mm isohyet) to November 25th (1,250 mm isohyet). At 650 to 800 mm annual rainfall, the average gum production per site varied from 100 to 500 g per tapped tree, corresponding to 50-250 kg/ha with a density of 500 trees/ha. However, in sites with annual rainfall higher than 1,000 mm, the gum production was generally lower and uncertain. Although the mean production on the different types of soil did not differ significantly when years were combined, the annual production was more variable and more dependent on climatic variations on sandy soils than on clay soils. The local Cameroon Laf provenance was more productive than foreign Sahelian (Senegal, Sudan) or Indian provenances. First observations and analyses of gum samples from the local provenance showed an outstanding brightness and classical properties typical of A Senegal exudates in the Sahel region.