Agriculture Reference
In-Depth Information
tAble 18.11
Regional and global fertilizer consumptions (n+P+k)
year
lath
America
--------------------------------10
6
nutrient tons -------------------------------------
world
south Asia
east Asia
sub-saharan
Africa
1961
31.2
0.5
3.1
0.16
1.0
1965
47.0
1.0
5.4
0.26
1.5
1970
69.3
2.8
8.3
0.44
2.9
1975
91.4
4.4
11.4
0.71
4.5
1980
116.7
7.4
21.1
0.96
7.5
1985
129.5
11.2
27.0
1.07
7.4
1990
137.8
15.2
36.5
0.25
7.9
1995
129.7
18.1
45.3
1.07
8.5
2000
136.4
21.6
45.5
1.23
13.2
2015
165.1
24.1
56.9
1.8
13.1
2030
188.0
28.9
63.0
2.6
16.3
Source:
IFDC, 2002; Bruinsma, 2003.
In addition to a positive nutrient flux into the agricultural soils, it is also impor-
tant to maintain a favorable elemental balance. The ratio of macroelements (nitro-
gen/phosphorus/potassium/calcium/magnesium) and micronutrients (zinc, copper,
molybdenum) must be maintained at a favorable level, and the concentration of some
toxic elements (aluminum, iron, manganese) must be kept low through use of bal-
anced fertilizer, application of manure, and use of lime. Government policies of sell-
ing nitrogenous fertilizers at subsidized prices have led to mining of phosphorus and
potassium in soils of South Asia. Such an elemental imbalance causes yield decline
even when the supply of nitrogen in the root zone is adequate.
Similar to the increase in crop production in South Asia, improving nutrient supply
through a judicious use of fertilizer input is also essential to enhancing crop yields in
sub-Saharan Africa. The data on kilogram per hectare of fertilizer use is the lowest
in sub-Saharan Africa and is projected to remain low (7 to 9 kg/ha) even by 2015 and
2030 (Table 18.12). Increase in fertilizer use in sub-Saharan Africa may necessitate
an increase in area under supplemental irrigation and improvement in water avail-
ability through soil-water conservation and water harvesting and recycling.
wAteR mAnAgement
Water conservation, recycling, and management aimed at enhancing the water use
efficiency are crucial to increasing and sustaining productivity in dry farming or
the rain-fed agroecosystems. Water management is especially important in the West
