Outgrowing the Earth Part 6

OUTGROWING THE EARTH

THE FOOD SECURITY CHALLENGE IN AN AGE OF FALLING WATER TABLES AND RISING TEMPERATURES

LESTER BROWN

EARTHSCAN          2005

PART VI

Chapter 4: Raising the earth’s Productivity

During the last half of the 20^th century the world’s farmers more than doubled the productivity of their land, raising grain yield per hectare from 1.1 tons in 1950 to 2.7 tons in 2000. Never before had there been an advance remotely approaching this one. And there may not be another.

• The unprecedented gains in land productivity were the result of the systematic application of science to agriculture.

The strategy of systematically applying science to agriculture while simultaneously providing economic incentives to farmers to expand output was phenomenally successful. Between 1950 and 1976, the annual world grain harvest doubled, going from 630 million to 1,340 million tons. In a single generation, the world’s farmers expanded grain production by as much as they had during the preceding 11,000 years since agriculture began.

Trends and contrasts

• The record rise in world grainland productivity since 1950 had three sources – genetic advances, agronomic improvements, and synergies between the two.
• The genetic contribution to raising yields has come largely from increasing the share of the planet’s photosynthetic product (the photosynthate) going to seed. Shifting as much photosynthate as possible from the leaves, stems, and roots to the seed helps to maximize yields.
• Although plant breeders have greatly increased the share of the photosynthate going to the seed, they have not been able to fundamentally improve the efficiency of photosynthesis – the process plants use to convert solar energy into biochemical energy.
• On the agronomic front, raising land productivity has depended on expanding irrigation, using more fertilizer, and controlling diseases, insects, and weeds.
• All these tactics help plants realize their genetic potential more fully.
• Japan has developed a highly productive rice culture, one based on the precise spacing of rice plants in carefully tended rows.
• Yet rice yields in Spain, California, and Australia are consistently 20% – 30% higher.
• The reason is simple. These locations have an abundance of bright sunlight, whereas in Japan rice is necessarily grown during the monsoon season, when there is extensive cloud cover.
• There are no high yields of any cereals – wheat, rice, or corn – in the equatorial regions. High yields come with the long growing days of summer in higher latitudes. The world’s highest whet yields are found in Western Europe.
• Western Europe occupies a northerly latitude comparable to that of Canada and Russia, but the warmth from the Gulf Stream makes its winters mild, enabling the region to grow winter wheat.
• Four environmental conditions – moderate winters, inherently fertile soils, reliable rainfall, and long summer days – combine to give the region wheat yields that reach 6 – 8 tons per hectare.
• The difference in wheat yields among leading producers worldwide is explained more by soil moisture variations than by any other variable.

 

Fertilizer and irrigation

In 1847 Justus von Liebig, a German chemist, discovered that all the nutrients that plants remove from the soil could be replaced in chemical form. This insight had little immediate impact on agriculture, partly because growth in world food production during the 19^th century came primarily from expanding cultivated area. It was not until the mid-twentieth century, when land limitations emerged, that fertilizer use began to climb. 

• When the world was largely rural, plant nutrients were recycled as both human and livestock wastes were returned to the land. But with urbanization, this natural nutrient cycle was disrupted.
• The shift from expanding cropland area to raising cropland productivity, coupled with accelerating urbanization, set the stage for the growth of the modern fertilizer industry.
• It enabled farmers to remove nutrient constraints on yields, thus helping plants to realize their full genetic potential.
• In many agriculturally advanced countries, fertilizer use has plateaued.
• There are still some countries with a large potential for expanding fertilizer use. One is Brazil, which is not only raising land productivity but also steadily expanding the cultivated area.
• For the world as a whole the era of rapidly growing fertilizer use is now history. In many countries, applying more fertilizer has little effect on crop yields.
• Where fertilizer application exceeds crop needs, nutrient runoff can contaminate water and feed algal blooms that lead to eutrophication and offshore dead zones.
• Paralleling the tenfold increase in fertilizer use during the last half of the last century was the near tripling of irrigated area.
• During the earlier part of this period, growth in irrigation came largely from the building of dams to store surface water and channel it onto the land through networks of gravity-fed surface canals.
• By the late 1960s as the number of undeveloped dam sites diminished, farmers in countries like India and China were turning to underground water sources.
• Millions of irrigation wells were drilled during the remainder of the century.
• Now the potential for building new dams is limited. So, too, is that for drilling more irrigation wells because the pumping volume of existing wells is already approaching or exceeding the sustainable yield of aquifers in key agricultural regions.

Over half of the world’s irrigated land is in Asia, and most of that is in China and India. Some four fifths of China’s grain harvest comes from irrigated land. This includes virtually all the riceland and most of the wheatland, plus part of the cornland. In India, over half of the grain harvest comes from irrigated land. And in the United States, irrigated land accounts for one fifth of the grain harvest.

• The growth in irrigation facilitated the growth in fertilizer use. Without irrigation in arid and semiarid regions, low soil moisture limits nutrient uptake and yields.
• The availability of fertilizer makes investments in irrigation more profitable.
• It is this synergy between the growth in irrigation and fertilizer use that accounts for much of the world grain harvest growth over the last half-century or so.

With irrigation as with fertilizer use, the growth worldwide has slowed dramatically over the last decade or so. Indeed, in some countries, such as Saudi Arabia and China, irrigated area is now shrinking. This is also true for parts of the United States, such as the southern Great Plains. In many parts of the world the need for water is simply outgrowing the sustainable supply.

The shrinking backlog of technology

• For wheat growers in the United States and rice growers in Japan, most of the available yield-raising technologies are already in use.
• Farmers in these countries are looking over the shoulders of agricultural researchers in their quest for new technologies to raise yields further. Unfortunately, they are not finding much.

From 1950 to 1990 the world’s grain farmers raised the productivity of their land by an unprecedented 2.1% a year, slightly faster than the 1.9% annual growth of world population during the same period. But from 1990 to 2000 this dropped to 1.2% per year, scarcely half as fast. (See Table 4-2.) As of mid-2004, it looks as though the annual rise in grain yields from 2000 to 2010 will drop to something like 0.7%, scarcely half that of the preceding decade and far behind world population growth. This loss of momentum in raising land productivity is due not only to the shrinking backlog of technology but also in some countries to the loss of irrigation water.

• Yields vary widely among countries. See Figure 4-4 for rice yields in Japan, China and India, 1960-2004; Figure 4-5 for wheat yields in France, China, and the United States, 1960-2004; and Figure 4-6 for corn yields in the United States, China, and Brazil, 1960-2004.

In 1990 IRRI launched a major research project to raise rice yields 25% – 50% by restructuring the rice plant. In the face of poor prospects for achieving this, the goal has now been scaled back to a rise of 5% – 10%.

• Can genetic engineers restore a rapid worldwide rise in grainland productivity? This prospect is not promising simply because plant breeders using traditional techniques have largely exploited the genetic potential for increasing the share of photosynthate that goes into seed.
• One major option left to scientists is to increase the efficiency of the process of photosynthesis itself – something that has thus far remained beyond their reach.
• Thus far the focus in genetically engineered crops has been to develop herbicide tolerance, insect resistance, and disease resistance.

When genetic yield potential is close to the physiological limit, further advances in yields rely on exploiting the remaining unrealized potential in the use of basic inputs, such as fertilizer and irrigation, or on the fine-tuning of other agronomic practices, such as optimum planting densities or more effective pest controls. Beyond this, there will eventually come a point in each country, with each grain, when farmers will not be able to sustain the rise in yields.

Future options

In a world where it is becoming increasingly difficult to raise land productivity, we have to look for alternative ways of expanding output. One obvious approach is to increase the amount of multiple cropping – growing more than one crop on a field per year. Yet this is not easy, and in some East Asian countries, such as Japan, South Korea, Taiwan, and, more recently, China, it is already declining.

• One of the keys to exploiting this lies in reorienting agricultural research programs to develop facilitating technologies such as earlier maturing crops and farm practices that will accelerate the harvesting of the first crop and the planting of the second one.
• Another way to expand food production is to raise water productivity. The water available for irrigation can be increased at the local level by building small water-harvesting ponds.
• These not only capture rainfall runoff, holding it for irrigation, they also help recharge underground aquifers.

Land productivity can be raised by using crop residues to produce food. For example, the tonnage of wheat straw, rice straw, and corn stalks produced worldwide easily matches the weight of grain produced by these crops. As India has demonstrated with its world leadership in milk production, and as China is showing with its surging beef production, it is now possible to feed these vast quantities of crop residues to animals, converting them into milk and meat. In effect, this permits a “second harvest” from the same land.

In some parts of the world, such as Africa, investment in transportation and storage infrastructure can play a major role in boosting food production, enabling farmers to move beyond subsistence agriculture. This is particularly helpful in both getting inputs such as fertilizer to farmers and getting their harvests to markets.

Jules Pretty, director of the Centre for Environment and Society at the University of Essex, has pioneered a broad concept of sustainable agriculture, one that strives to develop natural, human, and social capital at the local level. It emphasizes the use of local resources. Sustainable farming, says Pretty, “seeks to make the best use of nature’s goods and services. It minimizes the use of non-renewable inputs (pesticides and fertilizers) that damage the environment … it makes better use of the knowledge and skills of farmers.”

In reviewing the results of some 45 sustainable agricultural initiatives in 17 African countries, Pretty notes that both crop yields and nutritional levels improved more or less apace. Overall, he notes that crop yields are up 50% – 100% in these projects over 20 years.

Included in the sustainable agriculture toolbox is the better use of local natural resources and processes like nutrient cycling, nitrogen fixation, soil rebuilding, and the use of natural enemies to control pests. This approach does not rule out the use of fertilizer and pesticides but seeks to minimize the need for their use. The use of leguminous plants to supply nitrogen is seen as an intrinsic part of the process. Animal manures are collected to fertilize fields and build up soil organic matter. This, in turn, increases soil moisture retention.

The emphasis on human capital leads to greater self-reliance by farmers. Learning centers and extension offices play an important role in communities with successful sustainable agriculture. With social capital, the key is getting people to work together, in groups, to better manage watersheds and local forests or to supply credit to small-scale farmers.

With this approach, communities with marginal land have succeeded not only in raising incomes and improving diets, but also in producing a marketable surplus of farm products. Highly successful though this approach is, it does require substantial support to energize local communities. Pretty notes that “without appropriate policy support, these community projects are likely to remain localized in extent, and at worst simply wither away.”

The challenge is to raise land productivity in one way or another and to design research programs to do this while protecting the land and water resource base and avoiding damage to natural systems, such as that caused by nutrient runoff.

Chapter 5: Protecting Cropland