Growing cereals year after year in the same field drains the soil of essential nutrients and erodes productivity when nutrients are not replenished. And, like monoculture of any sort, it can encourage persistent pests and diseases.

Cereal monoculture in the West Asia and North Africa (WANA) region has encouraged a particularly sinister crop disease. It is caused by a microscopic parasitic worm, or nematode, that infests the plants and is particularly prevalent in North-West Syria, in areas with 250-300mm annual rainfall. Syrians call the disease Abou Alouwei, after the farmer in whose fields ICARDA researcher Mustafa Bellar first identified it. Abou Alouwei is such a tall man that it is said he waves in the breeze, like the infested stalks of barley. Abou Alouwei and his wife were childless for so many years that his neighbors, with grim humor, reasoned that he also shared another characteristic with the affected barley--the heads of which are sterile.

Nematodes are not the farmers' only problem in WANA. A small insect pest called "ground pearl" has also affected the region, but fortunately it can be eliminated by fallow or crop rotation and the use of clean seed for the next cereal planting. One solution is to rotate cereals with forage legumes such as vetches, something that ICARDA scientists had developed as a means of fixing nitrogen in the soil and boosting yields.

The use of vetch is not new. Traditionally, farmers grew it in rotation with cereals as feed for livestock and draft animals. It could be grazed green in late winter and early spring, when feed was short; it could be harvested early to make hay; or it could be left to mature, to provide grain and straw for winter feeding.

References to rotation with legumes date from Roman times, but the practice probably faded because farmers became less dependent on draft animals and population growth pushed up demand for cereals, tempting growers into monoculture. Until the 1950s, forage legumes accounted for 10-15 percent of the rainfed farming area in one Syrian province, but by 1988 it had plunged to just 2 percent.

Yet the system made good sense. In 1978, a report commissioned by ICARDA indicated that there were about 30 million hectares of fallow land in the WANA region suitable for pasture and forage legumes, and that if 70 percent of this were sown with vetches, it would produce enough feed for 80 million ewes. Some of the pressure caused by the overgrazing of sheep and goats on marginal semi-arid lands in the WANA region could possibly be eased by exploiting this potential.

ICARDA also estimated that vetches would return an additional 1.4 million tons of nitrogen to the soil each year-a figure equal to 165 percent of the nitrogen then applied as fertilizer in Afghanistan, Algeria, Iran, Jordan, Libya, Syria, Tunisia, and Turkey combined. These figures should be treated with caution however, because much depends on land management, environment and species, as subsequent research has confirmed. But even in situations where the effect of rotation with cereals is disappointing, the system can be beneficial.

Testing

In 1985, Jordanian researchers began a 10-year trial to compare the yield from barley sown after fallow, with that of barley rotated with forage legumes. Although the nitrogen-fixing effect of legumes is thought to be most effective with reasonable rainfall, the Jordanian trials were held at Ramtha where it rarely exceeds 250mm. The best yields were obtained after a barley/fallow rotation-but once livestock feed and meat prices were taken into consideration, the best net returns to farmers were from the barley/forage legume rotation, accompanied by sheep grazing during the legume year.

Trials by ICARDA at Tel Hadya and at Breda during the 1980s tended to support this conclusion while other trials suggested that, by producing a greater biomass overall, the barley/vetch rotation also provided better water-use efficiency-an important factor in an area of scarce water supply. Both the barley/fallow and the barley/legume options provided better yields than barley monoculture.

Adapting the technology

Since the mid-1980s, ICARDA has therefore encouraged the use of vetches to replace the fallow in cereal production. Evidence indicates that common vetch is the best species to use in areas with rainfall of around 300mm, but there are many different vetch species, and many different breeding lines within those species, that prefer lower or higher rainfall.

Increasing vetch yields

The shattering of pods can make seed harvesting difficult with vetch, but with careful selection and breeding, ICARDA scientists have been able to develop higher-yielding varieties with non-shattering pods.

A major difficulty common to any crop meant to rehabilitate degraded land is that it might be eaten before reaching maturity, but ICARDA was able to draw on a germplasm collection of more than 5,000 lines to identify a vetch that forms pods underground as well as above ground. Most of the seed held in ICARDA's bank has been collected within WANA, so they incorporate a wide range of locally-adapted characteristics.

Convincing farmers

Developing a technology off-farm is often just a beginning, however. For ICARDA's work to be useful, researchers must collaborate with farmers to ensure that there will be interest in adopting the end product.

One attraction of vetch is its versatility. It can be grazed green, cut for hay, or harvested at maturity for grain and straw. If mature harvesting is to be an inducement however, the cost of harvesting itself becomes an issue. Labor is, in real terms, not cheap in WANA, and this has been a factor in farmers' willingness, or otherwise, to adoption rates of other crops as well.

To complement production gains with vetch, ICARDA needed a low-cost method of mechanized harvesting. Working with local industry, it developed a roller to prepare the ground and a double-knife cutterbar for harvesting. The roller costs the equivalent of about US$3500 but it can be easily transported between fields so that farmers can share the investment. Hand harvesting of legumes costs Syrian farmers 2000-3000 lira (about US$50-75) per hectare.

An additional benefit of the new harvester is that farmers at El Bab in Northern Syria have found that it works well for barley as well. The roller allows them to increase their straw yields by cutting lower. They have also found that the new equipment makes it easier to harvest lodged barley.

Livestock gains

The economics of sheep grazing on forage legumes also look good. Grazing can eliminate the need for weeding, and this is important in areas such as El Bab where selective herbicides are not available. The daily weight gain at 30 lambs per hectare has been about 200 grams without supplementary feeding. The average weight of a five-month-old lamb raised on a vetch field is about 35 kg-the best weight at which to sell.

Transferring ideas

Explaining the interrelated benefits of vetch to farmers has been especially important. Any new idea can be difficult to transfer and when the technology offered is an update of something that they have themselves abandoned, farmers may be especially skeptical. On the El Bab project, many do not believe that forage legumes are especially productive and there is economic pressure for continuous cereal cropping. At El Bab however, the farmers are key players in the project and ICARDA is working with them to develop the most acceptable approach.

The vetch story illustrates another key point about agricultural research. There must be a systems approach. Cereals, vetches, livestock, soil conditions and market forces are all components of a complex pattern that we call agriculture. Any new effort must be slotted into that pattern, or farmers will not adopt it. Even worse, the change might ultimately prove to be harmful.