Agriculture Reference
In-Depth Information
TABLE 15.4
Average Country Nutrient Balances in Selected African Countries
Year (Average)
Henao and Baanante
Stoorvogel et al.
(N + P
2
O
5
+ K
2
O kg/ha)
(N + P
2
O
5
+ K
2
O kg/ha)
Country
1981-1985
2002-2004
% Change
1982-1984
2000
% Change
Benin
-37
-44.0
19
-27
-33
22
Botswana
-1
-47.0
460
-1
-4
300
Cameroon
-25
-44.0
76
-34
-41
21
Ethiopia
-56
-49.0
-12
-73
-102
40
Ghana
-32
-58.0
81
-50
-68
36
Kenya
-48
-68.0
42
-74
-91
23
Malawi
-42
-72.0
71
-144
-148
3
Mali
-34
-49.0
44
-18
-27
50
Nigeria
-35
-57.0
63
-72
-83
15
Rwanda
-101
-77.0
-24
-131
-158
21
Senegal
-38
-41.0
8
-26
-37
42
Tanzania
-44
-61.0
39
-58
-68
17
Zimbabwe
-12
-53.0
342
-62
-62
0
Source:
Henao, J., and C.A. Baanante,
Estimating Rates of Nutrient Depletion in Soils of Agricultural
Lands of Africa
, International Fertilizer Development Center, Muscle Shoals, Alabama, 1999;
Stoorvogel, J.J. et al.,
Fert Res
, 35, 227-235, 1993.
Note:
All data converted to N, P
2
O
5
, and K
2
O so that estimates could be directly compared.
studies—Henao and Baanante (1999, 2006) and Stoorvogel et al. (1993). The coun-
tries listed have been selected on the basis of the list published by Stoorvogel et
al. (Henao and Baanante had a more complete list). Both studies show consistently
high annual rates of nutrient depletion both in the early 1980s and 20 years later. In
most countries listed, both data sets show that over the 20-year periods shown, the
rates of nutrient mining continued to increase significantly. Several countries show
inconsistent trends in one or the other data set. Botswana, which has a relatively high
income, shows the lowest nutrient depletion between 1981 and 1985. This increases
significantly to 147 kg ha
−1
year
−1
in the 2002 to 2004 data of Henao and Baanante
but not Stoorvogel et al. Zimbabwe, on the other hand, had a low level of depletion
between 1981 and 1985 of 12 kg ha
−1
year
−1
, but in the equivalent period, Stoorvogel
et al. estimated a nutrient mining rate of 62 kg ha
−1
year
−1
. Finally, the data of Henao
and Baanante show a decline in nutrient mining rates in Rwanda from 101 to 77 kg
ha
−1
year
−1
, whereas the data of Stoorvogel et al. show the opposite trend and higher
rates of depletion. These inconsistencies aside, the major conclusion from the country-
level studies in Table 15.4 is that NUTMON-type national level balances show high
and continuing average rates of nutrient mining in most SSA countries listed.
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