Sustaining Yields in Irrigated Areas

Water covers about 70% of the Earth's surface. Of this total, only about 2.5% is fresh water, and most of this is frozen in the ice caps of Antarctica and Greenland, in soil moisture, or in deep aquifers not readily accessible for human use. Indeed, less than 1% of the world's freshwater — found in lakes, rivers, reservoirs, and underground aquifers shallow enough to be tapped economically — is readily available for direct human use. Irrigated agriculture, which accounts for 70% of global water withdrawals, covers some 17% of cultivated land (about 275 million ha) yet accounts for nearly 40% of world food production.

The rapid expansion in world irrigation and in urban and industrial water uses has led to growing shortages. The UN's Comprehensive Assessment of the Freshwater Resources of the World estimates that "about one third of the world's population lives in countries that are experiencing moderate-to-high water stress, resulting from increasing demands from a growing population and human activity (World Meteorological

Organization, 1997). By the year 2025, as much as two thirds of the world's population could be under stress conditions.

In order to expand food production for a growing world population within the parameters of likely water availability, the inevitable conclusion is that humankind in the 21st century will need to bring about a "Blue Revolution" to complement the "Green Revolution" of the 20th century. In the new Blue Revolution, water-use productivity must be wedded to land-use productivity. New science and technology must lead the way. Clearly, we need to rethink our attitudes about water, and move away from thinking of it as nearly a free good, and a God-given right. Pricing water delivery closer to its real costs is a necessary step to improving use efficiency. Farmers, irrigation officials, and urban consumers will need incentives to save water. Moreover, management of water distribution networks, except for the primary canals, should be decentralized and turned over to the users.

Many technologies exist to improve the efficiency of water use. Wastewater can be treated and used for irrigation. This could be an especially important source of water for periurban agriculture, which is growing rapidly around many of the world's megacities. By using modern technologies such as drip irrigation systems, water can be delivered much more efficiently to the plants and largely in ways that avoid soil waterlogging and salinity. Changing to crops that require less water (and/or new improved varieties), together with more efficient crop sequencing and timely planting, can achieve significant savings in water use.

Proven technologies such as drip irrigation, which saves water and reduces soil salinity, are suitable for much larger areas than currently used. Various new precision irrigation systems are also on the horizon, which will supply water to plants only when they need it. There is also a range of improved low-cost, small-scale, and supplemental irrigation systems to increase the productivity of rainfed areas, which offer much promise for smallholder farmers.

An outstanding example of new Green/Blue Revolution technology in irrigated wheat production is the "bed planting system," which has multiple advantages over conventional planting systems. Plant height and lodging are reduced, leading to 5% to 10% increase in yields and better grain quality. Water use is reduced 20% to 25%, a spectacular savings! Input efficiency (fertilizers and crop protection chemicals) is also greatly improved, which permits total input reduction by 25%. After growing acceptance in Mexico and other countries, India, Pakistan, and Shandong Province and other parts of China are now preparing to rapidly extend this technology.

Conservation tillage (no tillage, minimum tillage) is another technology that has important "water harvesting" and soil conservation characteristics. About 100 million ha are planted in such systems throughout the world. By reducing and/or eliminating the tillage operations, conservation tillage reduces turnaround time on lands that are double and triple cropped annually, which adds significantly to total yield potential, especially rotations such as rice/wheat and cotton/wheat. This leads to higher production and lower production costs. Conservation tillage controls weed populations and greatly reduces the time that small-scale farm families must devote to this backbreaking work. The mulch left on the ground reduces soil erosion, lowers soil temperatures, builds up organic matter, increases moisture retention in the soil profile, and reduces moisture loss through evaporation. These "water harvesting" aspects of conservation tillage may prove increasingly important in the future as water stress becomes more prevalent in many parts of the world.

3.4.2.1 Addressing Marginal Lands and Environments

As noted earlier, many of the world's poorest and socially and nutritionally disadvantaged people live in marginal environments and seek to make their living from marginal lands. Historical geologic events can substantially affect soil quality as can inappropriate agricultural practices characteristic of more recent times. Also, because of low levels of precipitation or cold temperatures, it is possible, for instance, to have a poor agricultural environment associated with fertile soils. For purposes of this discussion, however, we shall deal with three general topics, namely drought, problem soils, and low soil fertility. Once again, these are frequently but not always associated.

As noted elsewhere in this document, biotechnology offers many new and exciting opportunities to make more rapid progress in developing higher-yielding varieties better suited to harsh production environments. It appears that, with the aid of new scientific techniques and knowledge, considerable progress in being made in the areas of drought tolerance and avoidance, heat tolerance, tolerance to acid and/or saline soils, and mineral toxicities. There is also evidence that varieties can be developed that are more efficient at extracting otherwise unavailable soil nutrients or able to produce well with lower levels of nutrients or at higher levels of soil toxicities. This research needs to be substantially expanded and accelerated.

Particularly in disadvantaged areas, increasing farmer incomes depends on lowering fertilizer prices and enhancing the availability of cropping patterns and crop production systems that provide higher and more consistent returns to cultivators in high-risk environments. Restoring soil organic matter through various means, such as off-season green manure/cover crops, crop rotations with legumes, and livestock production in association with cultivated crops, need to be further investigated and where appropriate, promoted.

Better and more productive and economical systems of water harvesting and distribution are needed. Microirrigation systems, which use limited water supplies more advantageously and that are used along with the production of high-value crops must be developed.

Only through the public sector or public-private sector partnerships will the required investments in such research activities be made. Without these investments, many more poor people will be crowding the city slums in Third World countries and, from there, migrating to the city streets of the industrialized world.

3.4.2.2 Improving Nutritional Quality

Plant breeding can improve nutritional quality of staple foods. The development of quality protein maize (QPM) at CIMMYT during 1970 to 1990 is one such example. QPM carries the opaque-2 gene that doubles the levels of lysine and tryptophan — two essential amino acids needed to build proteins — over normal maize. It offers considerable nutritional advantages to humans and monogastric animals. QPM is also an excellent maize-based weaning food for poor people and reduces feed costs (by reducing the amount of protein components) for swine and poultry production.

Plant breeding offers the potential to reduce micronutri-ent deficiencies by increasing the concentration of micronu-trients within staple food crops, either to reduce inhibitors of micronutrient absorption or to raise the levels of amino acids that promote micronutrient absorptions. Natural genetic variation in many crops, including rice, wheat, maize, and beans, shows a wide range of concentration of iron, zinc, and other micronutrients. In addition, through biotechnology, pro-vitamin A can be introduced into rice, white maize, and other food crops.

This could have profound positive results for millions of people too poor to have access to balanced diets and food supplements.

3.4.2.3 What to Expect from Biotechnology

What began as a biotechnology bandwagon nearly 20 years ago has developed invaluable new scientific methodologies and products that need active financial and organizational support to bring them to fruition in food and fiber production systems. Initially, biotechnology had the greatest impact in medicine and public health. However, now several fascinating developments are apparent in agriculture. In animal biotechnology, bovine somatotropin (BST) is now widely used to increase milk production. In plants, transgenic varieties and hybrids of cotton, maize, and potatoes containing genes from

Bacillus thuringiensis, which effectively control a number of serious insect pests, are now being successfully introduced commercially in the United States and elsewhere. The use of such varieties will greatly reduce the need for insecticide sprays and dusts. Considerable progress also has been made in the development of cotton, maize, oilseed rape, soybeans, sugar beets, and wheat, with tolerance to several herbicides, which can lead to a reduction in overall herbicide use through much more specific interventions and dosages. Thus far, it is estimated that in the United States alone, pesticide use has been reduced by 21,000 metric tons per year in cotton, maize, and soybeans (Gianessi, 2002).

Substantial progress has been made in developing cereal varieties with greater tolerance for soil alkalinity, free aluminum, and iron toxicities. These varieties will help to ameliorate the soil degradation problems that have developed in many existing irrigation systems. They will also allow agriculture to succeed into acidic soil areas, such as the cerrados in Brazil and in central and southern Africa, thus adding more arable land to the global production base. Greater tolerance of abiotic extremes, such as drought, heat, and cold, will benefit irrigated areas in several ways. First, we will be able to achieve "more crop from every drop" through designing plants with reduced water requirements and adoption of moisture-conserving crop/water management systems. Second, enhanced drought tolerance can reduce the risks of food production in more marginal rainfed environments, thus significantly contributing to food security of some of the world's poorest people. Recombinant DNA techniques can speed up the development process.

There is growing evidence that genetic variation exists within most cereal crop species for genotypes that are more efficient in the use of nitrogen, phosphorus, and other plant nutrients than are currently available in the best varieties and hybrids. Scientists from the University of Florida and Monsanto have been working on the genetic engineering of wheat and other crops that have high levels of glutamate dehydrogenase (GDH). Transgenic wheat varieties with high

GDH are reported to yield up to 29% more with the same amount of fertilizer than do the normal crop (Smil, 1999).

Transgenic plants that can control viral and fungal diseases are not nearly so developed. Nevertheless, there are some promising examples of specific virus coat genes in trans-genic varieties of potatoes and rice that confer considerable protection. Other promising genes for disease resistance are being incorporated into other crop species through transgenic manipulations.

The biofortification work mentioned above will also be greatly enhanced and accelerated through the tools of genetic engineering, which allow us to reach beyond a particular species to other taxonomic groups, orders, and kingdoms. More nutritionally balanced foods can be expected in the future. They will have more balanced amino acids and higher levels of essential vitamins and micronutrients. Significant advances will also occur in what are often labeled "nutriceu-ticals," plants that can help control and cure diseases, and also serve to deliver vaccines to humans and livestock.

Since much biotechnology research is being done by the private sector, which patents its inventions, agricultural policymakers must face up to a potentially serious problem of access, especially for resource-poor farmers. How long, and under what terms, should patents be granted for bioengi-neered products? Further, the high cost of biotechnology research is leading to rapid consolidation in the ownership of agricultural life science companies. Is this desirable? These issues are matters for serious consideration by national, regional, and global governmental organizations.

National governments need to be prepared to work with — and benefit from — the new breakthroughs in biotechnology. First and foremost, governments must establish a regulatory framework to guide the testing and use of genetically modified crops. These rules and regulations should be reasonable in terms of risk aversion, and cost-effective to implement to avoid tying the hands of scientists through excessively restrictive regulations. Since much of the biotechnology research is underway in the private sector, the issue of intellectual property rights must be addressed, and accorded adequate safeguards by national governments.

3.4.2.4 Coping with Climate Change

Although considerable differences of opinion continue to exist as to the timing, severity, and differential effect of the actual climate change associated with global warming, a consensus seems to have emerged about three important aspects.

The first is that catastrophic weather events are likely to increase, taking the form of more severe storms, more flooding, and, of most concern for agriculture production, more frequent and severe droughts. Second, it appears possible that favored lands will experience even more favorable growing conditions but that areas that are currently subject to periodic flooding and, more particularly, drought, are likely to experience increased devastation. Third, virtually all agricultural research directed at overcoming the effects of heat, drought, and associated biotic and abiotic stresses will be of high potential benefit to ameliorating the likely negative effects of global warming.

It is fortuitous indeed that these same research priorities coincide with those most valuable and urgent in a "pro-poor" agricultural research agenda.

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