SPATIAL VARIABILITY IN SOIL CHEMICAL-PROPERTIES UNDER DACTYLADENIA-BARTERI, ALCHORNEA-CORDIFOLIA, SENNA-SIAMEA AND GMELINA-ARBOREA HEDGEROWS ON AN ACID ULTISOL

Spatial nutrient distribution was studied under a three-and-a-half-yea r-old fallow of Dactyladenia barteri, Alchornea cordifolia, Senna siam ea and Gmelina arborea hedgerows grown on an acid Ultisol in southeast ern Nigeria. The objectives were to evaluate the nutrient cycling capa city and suitability of the hedgerow species for alley cropping. No co nsistent patterns were observed in the lateral distribution of soil pH , total nitrogen, organic carbon, available phosphorus, exchangeable c ations (potassium, calcium, magnesium and sodium), total acidity and e ffective cation exchange capacity in the 4 m wide alleys formed betwee n the hedgerow species. Senna siamea and Gmelina arborea tended to inc rease soil organic carbon, calcium, magnesium and effective cation exc hange capacity, particularly in the top 50 cm, compared with Alchornea cordifolia and Dactyladenia barteri, and can therefore be recommended for soil fertility regeneration on acid Ultisols during periods of fa llow. However, they appear to be less suitable for alley cropping than Dactyladenia barteri because they are shallow rooting.