ECOLOGICAL STUDIES ON THE SEEDLING GROWTH OF THE AFRICAN WALNUT, <em>TETRACARPIDIUM</em> <em>CONOPHORUM</em>

Abstract

Studies on the growth response of the seedlings of the African walnut, Tetracarpidium conophorum, to the effects of full sunlight, shade, soil types, soil moisture conditions, soil pH, soil salinity and mineral nutrients were carried out in greenhouse experiments. The seedlings responded to the effect of full sunlight and shade in the same manner in terms of all attributes measured. There was significantly better growth under the moist soil condition than the dry condition. Waterlogged condition resulted in seedling death. Humus soil enhanced growth significantly better than the other soil types tested. While the seedlings in humus had the highest values in the mineral nutrients analysed, those in clay and sand had the least. Growth significantly increased with increase in soil pH. There was a steady decrease in seedling survival and growth with increase in soil salinity. There was also a steady increase in sodium content and a steady decrease in other mineral elements in the seedlings as soil salinity increased. The absence of either nitrogen, phosphorus or potassium from the culture solution resulted in reduced growth, but the absence of nitrogen had the most pronounced effect on growth. The results are compared to those of germination studies and discussed in relation to the ecology and distribution of the species.