It is a well-known fact that 80% of Malawi’s population depends on rainfed subsistence agriculture for their survival. Agriculture remains the largest economic activity contributing 28.7% of GDP and more than 80% of export earnings. This signifies that as a nation, productive soil is one of the most important resources nature has endowed us for our own survival. But for this newsletter we ask, what is the extent of the loss of soil through erosion and what is being done in Malawi to safeguard and manage this precious resource – soil?
Soil erosion is one of the many challenges the smallholder farmer has been facing in Malawi for decades. Heavily eroded fields are common sites; Cultivation on fragile soils, steep slopes and poor soil management practices are among top causes of erosion.\
Poor soil management causes serious damage to our national economy. A study report by FAO/UNDP (2014) found that the country loses an average of 29 ton per hectare per year of top soil. This causes serious depletion of the fertile soil needed to sustain agriculture productivity.
It is also estimated that every year, soil erosion reduces agricultural productivity by 6% putting less food on the table for many households. A World Bank (1992) funded study found out that up to 15.6% of yield is lost due to the top soil to erosion. The same report estimated that if soil erosion was be tackled, 1.88 million people could be lifted out of poverty within a decade.
Since colonial times, methods of husbandry and farming practices have been promoted with an aim to mitigate erosion. Ridge cultivation was designed to mitigate the problem of erosion and increase yields. Farmers were told to till soil and construct 30cm high ridges along contour markers and boxed furrows to prevent erosion. However, improper alignment of ridges, cultivation of steep slopes, fragile and shallow soil types, high intensity rainfall, and poor soil management practices have led to regrettable levels of erosion in this country.
Continued use of hand hoes and constant treading have over time created the hard pan that prevents proper root development, hinders water infiltration and promotes top soil saturation causing increased surface runoff
The government effort to safeguard and manage soil and water resources in agriculture production, under ridge cultivation as well as Conservation Agriculture farming, is being challenged. These are, however, still the most commonly promoted technologies in Malawi. Inevitably the next question would be whether there is any better technology that can help farmers manage soil and water to attain sustainable food and income security? The answer is, Yes! There is the Tiyeni Deep Bed farming method.
Deep Bed Farming is a package of government approved good husbandry practices that have been innovatively blended into a technology that, if applied together, is capable to stop soil erosion, build soil fertility and soil health, harvest rain water and increase absorption, increase rooting depth thereby improving crop health and performance (yield).
DBF is capable of mitigating soil loss, reducing floods, recharging aquifers, and reducing the cost of investment in soil due to enhanced ability to retain top healthy and fertile soils. But what key DBF elements help to stop soil erosion?
The DBF package has a number of good husbandry practices that are implemented together for effectiveness. This article outlines those that are critical to the control of soil erosion:
Breaking the soil hard pan. This is mandatory wherever there is such a physical barrier. The hard pan which is prevalent across Malawi must be broken before planting any crop, a recommended requirement by experts (FAO, 1999). Adoption of Zero Tillage must be on a soil with all physical and chemical limitations removed –hoe and plough hard pans especially need to be removed by cultivation. Farmers break the pan by deep tilling to a depth of not less than 30cm, generally using a pick axe to achieve this.
Construction of planting beds (Deep Beds). Once the area for deep bed cultivation has been selected, the contours are marked using a line level, and marker ridges are constructed following the contour. These ridges are strengthened with tough vetiver grass planted on them. The deep beds are constructed parallel to the marker ridges – therefore also following the contour – loosening the soil at depth as described above. The beds measure a metre across and are separated by furrows which also serve as paths – the beds being out of bounds for treading on.
The soil composing the beds remains permanently loose, allowing crop roots to grow deep and water to infiltrate rather than running over the surface. The furrows are closed at the ends and “stopped” at intervals to prevent the movement of water. No water flows off the area treated in this way. (See the 3rd picture following). The beds measure 100cm at the top separated by 50cm furrows.
Box furrows, close ends and raise footpaths. Boxed furrows, closed ends and raised footpaths are important elements in DBF.
These features allow water harvesting and ensure full percolation of rainfall into the subsoil. The moisture is readily available to crops and doesn't get lost as surface runoff.
Application of organic manure that cover beds. The beds are long-term structures that, once made, are used for many years. The beds are never stepped on to avoid compacting the soil again.