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World population and per capita cropland and irrigated land area (calculated from Postel, 1999; FAO, 2002; Lal, 2007; Stewart, 2009; Falkenmark et al., 2009; Bruinsma, 2009).

 
Cropland area Irrigated land area
Year Population Total Per capita Total Per capita
billions Mha ha Mha ha
1900 1.5 805 0.536 40 0.027
1950 2.5 1170 0.468 94 0.038
1970 3.9 1300 0.333 169 0.043
1980 4.5 1333 0.296 211 0.047
1990 5.2 1380 0.265 239 0.046
2000 6.3 1360 0.216 277 0.044
2030 8.1 1648 0.203 300 0.037
2050 9.2 1673 0.182 318 0.034



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Water requirements per kilogram of different agricultural products (Clay, 2004).

 
Product Water requirement by area Water requirement by weight
106 L ha−1 103 L kg−1
Potato (Solanum tuberosum L.) 3.50–6.25 0.5–1.5
Wheat 4.50–6.50 0.9–2.0
Rice 5.0–9.5 1.9–5.0
Sorghum NA 1.1–1.8
Soybeans 4.50–8.25 1.1–2.0
Sugarcane 10.0–15.0 1.5–3.0
Chicken NA 3.5–5.7
Cotton (Gossypium hirsutum L.) 5.5–9.5 7.0–29.0
Beef NA 15.0–70.0
Shrimp 10.0–100.0 1.0–300.0
NA, not available.



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Grain yields at rainfed crops in Africa (recalculated from Singh et al., 2009).

 
Grain yield Increase over 30 yr
Region Crop 1971–1975 2001–2005
kg ha−1 % yr−1
West Africa Millet 600 770 0.9
Sorghum 690 900 1.0
Maize 860 1230 1.4
Central Africa Millet 610 560 −0.3
Sorghum 660 880 1.1
Maize 790 930 0.6
East Africa Millet 1170 1380 0.6
Sorghum 800 1000 0.8
Southern Africa Maize 1810 2840 1.9
Sorghum 1270 1930 1.7



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Potential and farmer yield under rainfed conditions (recalculated from Rockström et al., 2007).

 
Yield
Country Crop Potential Farmer Potential:Farmer
Mg ha−1
India
Soybean 2.19 0.94 2.3
Groundnut 2.69 1.06 2.5
Sorghum (summer) 3.50 1.19 2.9
Sorghum (winter) 1.44 0.63 2.3
Pearl millet 1.94 0.69 2.8
Pigeonpea 1.50 0.56 2.7
Chickpea 1.82 0.75 2.4
Northeastern Thailand
Soybean 1.94 1.19 1.6
Groundnut 1.69 1.31 1.3
Maize 4.69 2.38 2.0
Sunflower 1.56 1.44 1.1
Vietnam
Soybean 2.19 1.31 1.7
Groundnut 3.81 1.56 2.4
Maize 5.19 3.31 1.6
Kenya
Maize 4.25 1.25 3.4