Environmental Engineering Reference
In-Depth Information
Table 11.8 Maize grain and cassava tuber yield under slash-and-burn and no-burn land
management systems at Nkawie
Land-use stage
Field type
1996
1997
1998
Annual cropping
Intercrop
Tonne per hectare
Slash-and-burn, no
Maize
-
2.04
1.92
external input (T
0
)
Cassava
-
14.75
13.88
Slash, no-burn,
Maize
2.18
2.02
1.94
external input (T
1
)
Cassava
10.74
13.50
15.00
Slash, no-burn with
Maize
3.16
3.02
3.16
4 t/ha
1
(T
2
)
Poultry manure (PM)
Cassava
22.13
19.54
24.94
(approx. 100-50-64 kg
NPK)
Slash, no-burn with
Maize
3.62
3.35
3.26
4 t/ha
1
PM (T
3
)
plus 30-20-20 kg NPK
Cassava
21.67
22.20
27.20
LSD (5%)
Maize
0.49
0.46
0.14
Cassava
2.65
4.55
7.19
Source: Amoakohene (1999)
Over the three-year period, 1996-1998, there was a general decline in maize
grain yield for all the treatments. Although the treatments were applied yearly, the
added nutrients could not sustain the initial yield of the three-year continuous
maize, which fed from the same rooting zone. On the other hand, because maize
is a short-season crop, the slow release of nutrients from organic matter (poultry
manure and vegetative biomass) may have failed to supply the nutrients needed
to synchronize with the optimum demand of maize for nutrients. In such a situ-
ation, the yield of maize may decline.
Nevertheless the T
2
and T
3
treatments sustained a basal grain yield of 3 t/ha
over the years. This is significantly higher than the average grain yield of 1 t/ha
on most smallholder farms in Ghana. Although the period of yield monitoring
was short, it is apparent that the T
2
and T
3
treatments hold a better promise
than T
0
and T
1
for sustaining higher grain yield in a continuous cropping
of maize.
In the case of cassava, there was a steady increase in tuber yield for T
1
and
T
3
with the latter treatment recording the highest yields over the years. The
observed steady increase in tuber yield over the years in respect of T
1
,T
2
, and
T
3
might be due to the fact that the crops stayed on the field for a longer
period, thus making optimum use of the nutrients mineralized and released
from the organic matter.
Burning (T
0
) gave the lowest tuber yield, which declined over the years as
observed for maize grain yield. Burning could therefore not sustain higher
crop yields.
