That poor soil fertility is the principal constraint to production in smallholder farming in Africa is widely acknowledged, with experts declaring soil fertility in the continent as being at stake.
The role of the agriculture as the primary source of livelihood in terms of food security, income generation, source of employment and foreign exchange earnings for most Kenyans cannot be gainsaid.
According to the “Green Economy Assessment Report” released in 2014, the sector contributes up to 65 percent of export earnings and 42 percent of employment. Small-scale farmers with farm sizes of 0.3-3 hectares contribute 75 percent of total agricultural production.
The sector is vulnerable to increasing droughts and floods which lead to soil erosion, deforestation and loss of soil fertility and productivity.
In a recent study on soil suitability for maize production, an analysis of samples from 4,800 smallholder farms in 164 sub-counties and 26 counties indicated a downward trend in all key fertility parameters.
A sample of the results from key breadbasket areas in western and upper Rift Valley areas showed more than 45 percent of farms had acidic soils which were also deficient in nitrogen, phosphorus and the microelement zinc. Over 80 percent of farms did not have the minimum organic carbon, or humus, as it is widely known.
This confirms that nutrient depletion is widespread.
The PH (acidity or alkalinity) of the soil influences nutrient availability and biological activity. Fertile soil should be 6.0-7.0. Acidity influences soil bacterial activity, affecting organic matter decomposition and nutrient availability.
Some 83-100 percent of the soils sampled did not meet the minimum humus threshold. Humus can hold up to seven times its weight in water. It is not surprising that our soils do not retain moisture, leading to droughts soon after good rains.
Ever since Malthusian times, the ability of the global food supply to feed the human population has been challenged. One side of the debate claims that green-revolution methods — including high-yielding plant and animal varieties, synthetic fertilisers, pesticides and now, transgenic crops — are essential to produce adequate food for the growing human population.
It was Ambrose Pritchar who opined that the erosion of soil fertility has been masked by a “soup of nutrients” poured over croplands, giving us a false sense of security while there is a 70 percent loss of the top soil.
Given the projection of 65 million Kenyans by 2030, it must be remembered that the Constitution, in Article 42, recognises a clean and healthy environment as a right. It calls for “sustainable exploitation, utilisation, management and conservation of the environment and natural resources”.
It is prudent that, to improve productivity, a sustainable and diversified system such as organic agriculture that places a healthy soil at the heart of production be embraced. This will ensure that the soil continues to supply life support services and reduce farmers’ vulnerability to crop failure due to effects of climate change.
As conservationist Gaba Dioum said, “In the end, we shall conserve only what we love, we will love only what we understand and we will understand only what we are taught”. Let’s love our soil!
Ms Kamau is an agriculture and environment expert. [email protected].