Environmental Engineering Reference
In-Depth Information
10
8
6
4
2
0
1&2
3
4
5
6
7
Week no.
Slash-no-burn
Slash-and-burn
Figure 14.9 Effects of slash-and-burn and slash without burning on mean stem diameter
of maize
Table 14.5 Total yield (kg) of maize obtained from
proka
and slash-and-burn fields
Farm practice
Total yield/kg
Mean weight per cob
Slash-no-burn (
proka
)
2.10
0.13
Slash-and-burn
2.40
0.15
Total represents weight of entire maize harvest.
plot when compared to the slash-and-burn plot where crops seem to have
performed more robustly in terms of vegetative vigour and yield (Table 14.5).
This finding is in sharp contrast to the finding reported for a PLEC demon-
stration site in the humid forest zone of central Ghana by Quansah and Oduro in
Chapter 11.
However, it is likely that, eventually, the
proka
system would contribute posi-
tively to crop growth and yield, since the release of mineral nutrients from
decomposed litter is a slow process (Markwei, 2002).
Conclusion
The preceding discussion suggests that the agronomic requirements of individual
crop species may be important when considering the combination of trees and
crops on farms, and that management of such trees in terms of pruning to elimin-
ate shade may be very important in designing agroforestry packages.
It is therefore likely that in general, field crops (e.g. corn and cassava) that require
higher light intensity may do relatively poorly even under trees that are known to
