Environmental Engineering Reference
In-Depth Information
Materials and method
Towards a better understanding of the efficiency of tree/crop combinations
in traditional agroforestry, growth and yield studies were conducted into the
following:
•
maize under
Cordia millenii
•
cassava under
Ceiba pentandra
•
cassava under
Cola millenii
cocoyam under
Cola millenii
.
In each case, concentric rings were drawn at two-metre intervals from the
bole of the selected tree. Five crops in each concentric ring were tagged and
measured. The parameters considered for measurement were leaf length (
l
),
leaf width (at 0.5
l
) and numbers, plant height (
h
), diameter of crop (at 0.5
h
),
and crop yield.
For the
proka
study, one half of the field was slashed and burnt, while the
other half, after slashing, was left unburnt with the slashed materials left in place
as mulch. Maize was planted on both the slashed-burnt and slashed but unburnt
fields. Weeding in the two fields was done after three weeks.
•
Soil sampling
Five soil samples were collected in each field from the four different corners and
centre of the field. At each collection point, soil samples were taken at five differ-
ent depths: 0-5 cm; 5-10 cm; 10-15 cm; 15-20 cm; 20-30 cm. Soils of
corresponding depths were bulked.
Soil nutrient analysis
Analyses of the soil nutrient content of both slashed and burnt and slashed
unburnt fields were carried out at intervals of four weeks for pH, available nitro-
gen, potassium, calcium, phosphorus, and organic matter content.
Soil pH was measured potentiometrically and organic matter was determined
by the wet oxidation method (Wallkley and Black, 1934). Total nitrogen was
determined by the Kjeldahl method, available phosphorus by the Bray and Kurtz
No. 1 method, and potassium levels by flame photometry.
An analysis of variance using stratigraphics was subsequently carried out to
determine the effects of:
•
different tree/crop combinations and varying distance from tree trunk
•
slash-and-burn and slash-without-burning practices on the growth and yield of
experimental crops.
