"Eliminating water shortages depends on a global attempt to raise water productivity similar to the effort launched a half-century ago to raise land productivity, an initiative that has nearly tripled the world grain yield per hectare." –Lester R. Brown, World Facing Huge New Challenge on Food Front in Plan B 3.0: Mobilizing to Save Civilization
Chapter 9. Feeding Seven Billion Well: Rethinking Land Productivity
Efforts to raise cropland productivity are slowing as the backlog of unused agricultural technology shrinks. The loss of momentum in efforts to raise cropland productivity is worldwide. Between 1950 and 1990, world grain yield per hectare climbed by 2.1 percent a year. From 1990 to 2000, however, it rose only 1.2 percent annually. This is partly because the yield response to the additional application of fertilizer is diminishing and partly because irrigation water supplies are limited. During the current decade, the rise in land productivity may slow even more. 5
This calls for fresh thinking on how to raise cropland productivity. One simple way of doing this, where soil moisture permits, is to increase the area multicropped—land that produces more than one crop per year. In North America and Western Europe, which in the past have restricted cropped area to control surpluses, there is some potential for double cropping that has not been fully exploited. Indeed, the tripling in the world grain harvest since 1950 is due in part to impressive increases in multiple cropping in Asia. Some of the more common combinations are wheat and corn in northern China, wheat and rice in northern India, and the double or triple cropping of rice in southern China, southern India, and nearly all the rice-growing countries in Southeast Asia. 6
The double cropping of winter wheat and corn in the North China Plain boosted China’s grain production to the U.S. level beginning two decades ago. Winter wheat grown there yields close to 4 tons per hectare. Corn averages 5 tons. Together these two crops, grown in rotation, can yield 9 tons of grain per hectare per year. China’s double-cropped rice yields 8 tons per hectare. 7
Forty years ago, North India produced only wheat, but with the advent of the earlier maturing high-yielding wheats and rices, the wheat could be harvested in time to plant rice. This wheat/rice combination is now widely used throughout the Punjab, Haryana, and parts of Uttar Pradesh. The wheat yield of 3 tons and rice yield of 2 tons combine for 5 tons of grain per hectare, helping to feed India’s 1.1 billion people. 8
The area that can be multicropped is limited by the supply of irrigation water and, in some areas, by a lack of enough labor to quickly harvest one crop and plant another. The loss of low-cost rural labor to industrialization can sharply reduce multiple cropping and therefore the harvested area. In Japan, for example, the grain harvested area peaked at nearly 5 million hectares in 1960 largely because the country’s industrious farmers were harvesting two crops per year. As of 2005, Japan’s harvested area had dropped to 2 million hectares in part because of cropland conversion to nonfarm uses, but mostly because of a steady decline in double cropping over the decades as rising wages in industry pulled workers away from agriculture. The cheap labor needed to cultivate small plots intensively has disappeared. Even a rice support price four times the world market level could not keep enough workers in agriculture to support extensive multicropping. 9
Similarly, South Korea’s harvested grain area has shrunk by half since peaking in 1965 primarily because of a decline in multiple cropping. Taiwan’s has declined nearly two thirds since 1975. As industrialization progresses in China and India, their more prosperous regions may see similar declines in multiple cropping. In China, where incomes have quadrupled since 1980, this process already appears to be reducing production. 10
In the United States, the lifting of planting area restrictions in 1996 opened new opportunities for multiple cropping. The most common U.S. double cropping combination is winter wheat with soybeans as a summer crop. Six percent of the soybean harvest comes from land that also produces winter wheat. Since soybeans fix nitrogen, this rotation reduces wheat farmers’ need to apply fertilizer. 11
A concerted U.S. effort to both breed earlier maturing varieties and develop cultural practices that would facilitate multiple cropping could substantially boost crop output. If China’s farmers can extensively double crop wheat and corn, then U.S. farmers, at a similar latitude and with similar climate patterns, could do the same if agricultural research and farm policy were reoriented to support it.
Western Europe, with its mild winters and high-yielding winter wheat, might also be able to double crop more with a summer grain, such as corn, or with an oilseed crop. Elsewhere, Brazil and Argentina have an extended frost-free growing season that supports extensive multicropping, often wheat or corn with soybeans. The availability of chemical fertilizers also facilitates multiple cropping. 12
In many countries, including the United States, most of those in Western Europe, and Japan, fertilizer use has reached a level where using more has little effect on crop yields. There are still some places, however, such as most of Africa, where additional fertilizer would help boost yields. Unfortunately, sub-Saharan Africa lacks the infrastructure to transport fertilizer economically to the villages where it is needed. As a result of nutrient depletion, grain yields in much of sub-Saharan Africa are falling. 13
One encouraging response to this situation in Africa is the simultaneous planting of grain and leguminous trees. The trees start to grow slowly, permitting the grain crop to mature and be harvested. Then the trees grow quickly to several feet in height, dropping leaves that provide nitrogen and organic matter—both sorely needed in African soils. The wood is then cut and used for fuel. This simple, locally adapted technology, developed by scientists at the International Centre for Research in Agroforestry in Nairobi, has enabled farmers to double their grain yields within a matter of years as soil fertility builds. 14
Despite local advances, the overall loss of momentum in expanding food production is unmistakable. It will force us to think about both limiting the growth in demand and using the existing harvest more productively. On the demand side, achieving an acceptable worldwide balance between food and people may now depend on stabilizing population as soon as possible, reducing the unhealthily high consumption of livestock products in industrial countries, and restricting the conversion of food crops to automotive fuels. But we must also think more broadly about land productivity, considering not only the individual crop but how to increase multiple cropping and how to get more out of existing harvests.
5. USDA, op. cit. note 1.
7. John Wade, Adam Branson, and Xiang Qing, China Grain and Feed Annual Report 2002 (Beijing: USDA, 2002); USDA, op. cit. note 1.
8. Double-cropping yields from USDA, India Grain and Feed Annual Report 2003 (New Delhi: 2003); population from United Nations, op. cit. note 4; USDA, op. cit. note 1.
9. Grain harvested area from USDA, op. cit. note 1; USDA, Japan Grain and Feed Annual Report 2003 (Tokyo: 2003).
10. USDA, op. cit. note 1.
11. Richard Magleby, “Soil Management and Conservation,” in USDA, Agricultural Resources and Environmental Indicators 2003 (Washington, DC: February 2003), Chapter 4.2, p. 14.
12. USDA, op. cit. note 1; Randall D. Schnepf et al., Agriculture in Brazil and Argentina (Washington, DC: USDA Economic Research Service (ERS), 2001), pp. 8–10.
13. FAO, op. cit. note 3; USDA, op. cit. note 1.
14. Pedro Sanchez, “The Climate Change–Soil Fertility–Food Security Nexus,” summary note (Bonn: International Food Policy Research Institute, 4 September 2001).
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