Environmental Engineering Reference
In-Depth Information
than T
2
. However, as indicated by Kang and Balasubramanian (1990) the
presence of organic matter through the addition of the poultry manure could
have enhanced the efficiency of uptake of the readily available nutrients in the
fertilizers by the test crops. In such a situation, the level of nutrients in the soil
may either be the same or less than what was recorded under T
2
. However,
efficient uptake of nutrients may result in higher crop yields in T
3
than T
2
(Table 11.8).
Mulching rates versus nutrient, runoff, and soil losses
For lack of data at the PLEC sites, the data in Table 11.6 (Quansah
et al.
, 2000)
are used to demonstrate the effect of
proka
on soil, runoff, and nutrient losses.
The experiments were carried out on runoff plots at the University of Science and
Technology, Kumasi, which is about 20 km from Tano-Odumasi. The soil was a
ferric acrisol with a slope of 3.5 per cent. The mulching material consisted of dry
guinea grass,
Panicum maximum
. The land-use stage was annual cropping with
maize as the field type.
The results showed mulching to reduce both soil loss and runoff in a decreas-
ing order of bare
6 t/ha mulch. As
the mulching rate increased, the soil loss and runoff decreased. Similarly, organic
matter and nutrient losses declined with an increasing rate of mulching. The
maintenance of mulch on the soil surface has been found to protect the soil
against raindrop impact, impede the flow of runoff, reduce nutrient losses, soil
detachment, and dispersion, and maintain high soil infiltration rate (Lal, 1976;
Roose, 1976).
The high losses of organic matter are of particular concern because it plays
a significant role in the nutrient and water-holding capacities of soils.
no mulch
2 t/ha mulch
4 t/ha mulch
Table 11.6 Nutrient runoff and soil losses due to different mulching rates
Organic
Available
Available
Total N
matter
Soil loss
Treatment
P (kg/ha)
K (kg/ha)
(kg/ha)
(ha-mm)
Runoff
(t/ha)
Bare (T
0
)
0.019
0.677
8.694
165.375
59.420
2.835
No mulch (T
1
)
0.011
0.559
5.188
70.144
39.287
2.192
2 t/ha (T
2
)
0.006
0.281
3.418
38.103
30.929
1.335
4 t/ha (T
3
)
0.005
0.240
2.799
36.607
29.010
1.615
6 t/ha (T
4
)
0.002
0.130
1.553
24.987
26.578
1.013
LSD (0.05)
0.0027
0.010
0.775
21.660
22.151
1.774
Source: Quansah
et al
. (2000)
