Restoring degraded soils for productivity

Soils threatened by water and wind erosion, nutrient depletion and salinization, among other things, which means loss of soil quality are most likely to lose their productivity. Although on a global scale soil loss is unlikely to be a major threat to food security, the impacts are probably going to be felt at the local and regional levels where farmers are too poor to overcome the damage.

Billions of tons of carbon, previously trapped in soil are released by mechanized farming to the atmosphere as carbon dioxide and methane. Lack of carbon in the soil makes crop production inefficient, resulting in low yields.

Global warming is most likely to make things worse. Organic matter decomposes more easily as the ground heats up, reducing soil fertility, releasing carbon dioxide and further exacerbating the warming effect. Soil erosion already contributes to global warming, as some of the carbon in soil-laden water running off fields inevitably escapes into the atmosphere. Deserts are expected to expand as the interiors of continents become drier and erosion would worsen if soils dried out and violent storms become more frequent.

There would be less organic matter in the soils of a hotter world. This will have tremendous consequences for farmers the world over for those farming in the marginal areas of developing countries. Critical regions of soil degradations and a high priority for soil restoration and carbon sequestration (storing carbon in soil securely so it is not immediately reemitted) include sub-Saharan Africa, central and south Asia, the Andean region, the Caribbean and the acid savannas of South America.

Fortunately, something can be done by managing soils to stem erosion and retain more carbon with composting. Compost is a natural fertilizer, supplying soils with vital plant nutrients and aiding them to retain water and air. It restores soil carbon crucial in maintaining consistent yields through improvements in water and nutrients holding capacity, soil structure and biotic activity. Food plant yields from using compost are comparable and, often higher, than those from chemical fertilizers.

The materials (dry leaves, grasses, maize stalks, and other biodegradable substances) for composting are mixed with soil and water, then left to decompose for sometime. The heat generated during the process destroys most weed seeds, fungal diseases, parasites and pests. Although farmers have to invest time and effort into making good compost, the rewards are worth the effort. The positive effects of compost on yields last for two or more cropping seasons.