Green manuring slow to catch on in Tanzania

Although tropical legumes are widely promoted as desirable components for low cost agricultural improvement for Tanzania, its adoption is rambling at a snail`s pace, according to experts.

Agricultural scientists have long provided evidence that legumes fix their own nitrogen from the atmosphere, and hence a form of green manuring option for agri-business, which can maintain or improve soil fertility without direct costs for fertiliser.

Acting Director for Research and Development at the Ministry of Agriculture, Food Security and Co-operatives, Timothy Kirway lamented that tropical legume crops yield in sub-Saharan Africa "remains very low as the crops are generally grown in marginal environments under rain-fed conditions with erratic patterns."

He said the productivity of selected legume crops such as beans, chick pea, cowpea, groundnuts, pigeon pea and soya beans did not reach much small, marginalised farmers due to poor public sector seed multiplication and delivery systems.

Legumes fix atmospheric nitrogen in symbiosis with bacteria and make it available to plants. The element nitrogen occurs in the green colour (chlorophyll) of plants and is responsible for the natural process of vegetative growth. In addition, the rotational benefits commonly observed following crop legumes may be derived partly from their contribution to `breaking` cycles of cereal pests and diseases.

Nitrogen fixed by legumes is however not `totally free` as the costs for green manure nitrogen include seed and the seeding costs, stand termination and residue incorporation costs, and lost revenue, since there is no cash crop produced during the year of plough down.

IPP Media