Sir

I commend and support Willy Verheye's suggestion in Correspondence1 that improved road systems to markets and fair price-setting will allow inland African farmers to compete better with those who sell cheaper imported foods. However, his corollary suggestion of using the “large untapped land-use potential” in this part of the world to increase food production is contrary to sensible notions of development and land management, for several reasons.

First, the few data available on land resources are unreliable. The FAO World Resources Report2 cited by Verheye was intended to highlight the global-resources aspects of the 28 major soil association groups and of their continental distribution on a 1:25 million map. Only one page (page 28) and one table (Table 11, containing some obvious errors) are devoted to land-resources reserves, and no details are given for how the data for the developing countries were obtained. The accuracy of the data at the scales used for the preparation is doubtful: each map unit includes various soil types and possible land uses2. Further, many specialists would dispute the data on cultivable reserves — for example, there is one estimate3 of possible arable expansion of 500 million ha for the whole world, which differs greatly from the 622 million ha for Africa and 696 million ha for South America in the FAO report2.

Second, current attitudes about nature conservation and development are strongly against further unchecked deforestation, which is likely to speed up soil erosion and land degradation, as well as having negative effects on biodiversity and possibly on global climate change. The remaining forests in Africa and elsewhere must be protected from further destruction, in order to promote a global sustainable geo-ecosystem. The World Bank is now rightly promoting economic development with complementary environmental conservation. African governments should follow this lead.

Yet Verheye is correct to say that solving Africa's food-production problem is, in principle, relatively simple. Food security for the growing population does not necessarily mean expansion of cultivated soil areas, but rather improved soil care and nutrient management on existing arable soils. Despite the increased production in recent decades, the average yields of cereals in Africa are still only one third of those in Europe and North America (ref. 3 and the FAO annual yearbooks). Yields per hectare of most crops in developing countries are only a fraction of what they could be under proper soil care and nutrient management, as shown by several Israeli and other demonstration projects in developing countries. Good soil care and land-use management involves soil testing, rotation, terracing and appropriate tillage, integrated with nutrient and moisture management4. Soils in practically all African countries are depleted of nitrogen, phosphorus and potassium. This nutrient depletion is probably increasing because of monocropping and insufficient resupply5,6. The vicious cycle of marginal inputs producing marginal yields resulting in marginal living standards must be broken.

In addition to improving the transport system, as Verheye suggests, the current subsidy and overseas aid should be used to provide the fertilizers and improved planting materials that are needed. Many locally trained soil and extension specialists living in the region are needed to transform the economy from one of small rural farmers to one of market food production7,8. At least ten dedicated extension soil scientists per million of rural population with problem-solving skills would be a good start.