Agriculture and Environment: Soybeans

Environmental Impacts of Production: Soil Erosion

Globally, some progress is being made on the issue of soil erosion.

One 1996 study in the United States showed that soil erosion associated primarily with soybean and corn production in the Midwest fell from 37.5 metric tons per hectare in 1930 to 19.5 metric tons per hectare in 1982 and to 15.75 metric tons per hectare in 1992 (Schnittker 1997).

Highly erodible lands being used
This rate is easily still a few times greater than is sustainable (defined as a creation of soil greater than or equal to that lost through erosion). Despite the progress, there is reason for concern as lands classified as "highly erodible" are now being used for soybean production.

In the United States, the Conservation Reserve Program actually paid producers to take highly erodible land out of production. It now appears that the development of herbicide-tolerant ("Roundup-ready") soybeans has encouraged many producers to plant at least some of those lands again.

Genetically modified soybean varieties
The soybean varieties genetically modified to tolerate herbicides allow producers to employ no-till and conservation tillage production systems to minimise erosion, even on the most erosion-prone areas. However, the net environmental impact of this change in cropping has yet to be determined.

The chief fear with the highly erodible lands is that, despite improved techniques, soil erosion will once again become a problem. The Brazilian National Development Bank has warned that "without well defined technical criteria" the soil in many areas of the Amazon could be rendered unusable by soybean cultivation.

Soil compaction
Soybean production also causes soil compaction. In Bolivia, where soybean cultivation has been increasing since the 1970s as a result of investments in crop substitutes for coca production, degradation is already severe.

Initially, soybeans could be cultivated without fertiliser or lime applications. By the late 1990s, however, more than 100,000 hectares of former soybean lands were abandoned to cattle pasture because the soil was exhausted. The 3 Mennonite settlements that had farmed soybeans had moved further to the north to clear more forests to, once again, plant soybeans.