UNIVERSITY OF AGRICULTURE, ABEOKUTA OGUN STATE ...

Composite soil samples were taken in February before plot layout, before planting. However, the
site vegetation had been burned by accidental :firethen. Therefore, another location close to the
site but unaffected by :firewas sampled. The composite surface (0- 15cm) soil samples were airdried
and passed through
a 2 mm sieve for particle size distribution and soil chemical analyses.
Also, a fraction of the soil sample was ground and passed through
0.5 mm sieve for organic
carbon determination. "Undisturbed" core samples (0- 6 em) were also taken for bulk density
determination in March after plot layout and tillage. Procedures and methods used for soil
chemical analyses are described by UTA (1979) and Anderson and Ingram (1993) whereas those
used for soil physical properties are described by Klute (1986).
Particle size distribution was determined by pipette method (Gee and Bauder, 198, Sheldrick and
Wang, 1993). Fifty grams of each soil sample was dispersed in a plastic bottle with sodium
hexamataphosdphate
overnight after the removal of organic matter by the addition of hydrogen
peroxide. It was then shaken overnight before being turned into a 1000 ml
measuring cylinder
for measurement with pipette at specified depth related to room temperature. Gravel content of
air-dried soil was measured by collecting gravel retained on 2 mm sieve and weighing it relative
to the total soil weight.