| dc.description.abstract | The study was conducted between January 1997 and February 2000 in a semiarid
area located at the University of Nairobi's Institute of Dryland Research,
Development and Utilisation, located at Kibwezi. The purpose was to determine the
changes that occur in soil carbon and nutrients (total soil nitrogen and available
phosphorus) when a natural ecosystem is cleared to make way for cultivation of under
local agronomic practices. The experimental design used was a 5x 3 Latin square design
witha slight modification in which the treatment plots were spaced over the entire fenced
off area to take care of the heterogeneity of soil texture and nutrients common to semi
arid and arid regions. Plots measuring 20 x 20 m were marked in an enclosed area 2
hectares in size. Fifteen of plots were randomly assigned to five treatments in 3 blocks of
replicates. The treatments were natural ecosystem, maize sown with goat manure, maize
intercropped with pigeon peas and maize sown alone.
At the beginning of each of the six growing seasons, soil samples were collected
using a soil augur at Q - 20, 20 -40 and 40- 60 cm depths. The levels of total soil
organic carbon, total soil nitrogen and available phosphorus were then determined. Soil
moisture content was determined at this point of the season and every fortnight
thereafter. Net nitrogen mineralisation was determined in.seasons 2, 3 and 6 using the
aerobic laboratory incubation from soil samples collected-;,over the growing season. At
the end of each growing season, dry maize yield (kg ha-I | en |
