Root Distribution of Two Woody Species Grown on Farmers’ Fields in the Southern Guinea Savannah Zone of Nigeria.

Trees play a significant role in improving soils for crop production through root activities. This study was carried out on four farmers’ fields in Mokwa, central Nigeria in May 1999 to quantify root distributions of 2-year-old Gliricidia sepium (G. sepium) and Acacia leptocarpa (A. leptocarpa). Root samples were taken up to 300-cm soil depth. Root length, surface area, and volume densities were evaluated by using Delta-T Scan device. Mass density was also evaluated. Root length densities of G. sepium ranged from 0.56–11 mm mL−1 while those of A. leptocarpa ranged from 0.13–5.93 mm mL−1, declining with soil depth. Potential contribution of roots to soil total porosity was less than 3%. Soil bulk density ranged from 1.28–1.51 g cm−3 under G. sepium and from 1.29–1.61 g cm−3 under A. leptocarpa. Although G. sepium had relatively more roots deeper in the soil than A. leptocarpa, both trees demonstrated deep rooting, suggesting that the trees would improve soil productivity if sufficient fallow length were allowed. [ABSTRACT FROM AUTHOR]