Francis Ayieko
4 February 2008
Nairobi — The urgency to restore soil fertility in Africa stems from the fact that more than three-quarters of the farmland in sub-Saharan Africa has been so depleted of the basic nutrients that crops need for survive, leading to reduced crop yields.
The soils are also low in organic matter and have poor water holding capacity. Experts warn that until these conditions are reversed, food production in Africa will remain depressed. They also say that unsustainable land practices are contributing to massive erosion and deforestation.
According to experts, much of Africa's soils are ancient, derived from granite weathered over millennia. But soil conditions have worsened in recent decades. Driven to meet the food demands of a growing population, African farmers have steadily abandoned traditional practices that restore soil nutrients, such as leaving fields fallow for several years between plantings.
It is estimated that continuous cultivation without soil revitalisation causes the loss of eight million tonnes of soil nutrients each year.
Today, there are 95 million hectares of degraded land in sub-Saharan Africa, leading to greatly reduced farmland productivity.
In the past, traditional farming practices maintained soil fertility by allowing fields to lie fallow for a few years. But population growth and pressure on land have led to a sharp decline in fallowing. Today, fallowing is practised on less than 25 per cent of land in 29 African countries and is expected to disappear entirely from 20 of those countries in the near future.
On the other hand, few small-scale farmers in sub-Saharan Africa are able to use fertilisers to restore soil health - because they either cannot get or afford the appropriate inputs. Today, sub-Saharan Africa uses one-tenth of the fertiliser commonly applied on farms around the world.
In addition, there is an art and science to the efficient and environmentally responsible combination of fertilisers, organic inputs and cropping techniques to get a maximum return on investment.
Finding the right combinations requires the best farmer knowledge and technical knowledge. For example, many soils respond poorly to the application of fertilisers or of organic matter alone. They often require rehabilitation with the right combinations of both and appropriate soil management practices.
According to agricultural experts, achieving the level of soil health critical to sustainable and adequate food production in Africa requires a variety of activities that will simultaneously improve soil management and land use practices while increasing farmer access to fertilisers and to the knowledge needed for their efficient and environmentally sound use.
Statistics show that during the 2002-2004 farming season, 85 per cent of African farmland, most of it in sub-Saharan Africa, experienced moderate annual losses of at least 30 kilogrammes of nitrogen, phosphorous and potassium, and 40 per cent of farmlands experienced high losses of more than 60 kilogrammes per hectare.
It has also been confirmed that nutrient losses are higher in particular regions. For example, annual losses on farmlands bordering rivers and on the dry savannahs of Mali, Burkina Faso, Nigeria, Ethiopia, Somalia and Kenya can be as high as 100 kilogrammes per hectare.
And agriculture lands developed on coastal sediments in Senegal, Gambia, Benin, Somalia, Kenya and Mozambique are losing up to 120 kilogrammes per hectare.
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