Nourishing the soil and producing sustainable yields

The Mucuna vines climb up the corn stalks and engulf the field three months after the corn harvest. In dry season the Mucuna dies back. When the rains start we plant corn seed directly in the mulch.

The corn was finally harvested from the small experimental field in the ACDI demonstration garden in January. Antoine set the husked ears in the sun for another week. Then the research guys shelled the corn, cleaned the seed and weighed it: 69 kilograms of gleaming white kernels filled two large basins.

No Iowa corn master would be impressed. Even an indifferent Iowa farmer produces 3 times as much per unit of land as we did in this small experiment. Still the 69kg translates into 1,586 kg/ha. And that is on a plot of weathered, sandy soil, using no fertilizers, in the sixth year of continuous corn cultivation on the same plot. To put the yield in perspective: a Congolese woman planting corn on a newly opened forest field would be delighted to produce 700 to 1,000 kg per hectare. And even she would never consider planting a second crop of corn on the same land until several years later.

How do we do it? The secret is the nitrogen-fixing capacity of the leguminous cover crop that follows the corn each year. Mucuna pruriens is a vigorous bean plant that buries the field in 3 feet of lush vegetation during the second rainy season. The leaves, vines and roots store up nitrogen. When the rains start again we plant the next corn crop. The nitrogen locked up in the decomposing organic matter is released, nourishing the young corn plant and favoring rapid growth. When the corn is maturing the next Mucuna cover crop is already developing. We harvest the corn and the cycle continues.

Agronomists have estimated that the Mucuna cover crop provides the equivalent of 17 to 35 bags of mixed chemical fertilizer for each 2.5 acres of land. That's about $1800 worth of fertilizer at current Kinshasa prices.

The yield in the experimental field was down a bit this year. But still the average over the last five years has been 1,733 kg/ha, about twice the yield in a traditional Congolese corn field - despite continuous cropping. This looks like one productive alternative to traditional slash and burn agriculture. Corn-Mucuna is one way to increase productivity and income and reduce the human footprint on increasingly scarce prime** agricultural land. That's the kind of stewardship ACDI is trying to encourage.


** "prime" agricultural land in much of Bandundu is misleading. These are old soils. They are highly weathered, stripped of most of their basic nutrients and chemically altered, impairing their capacity to hold on to nutrients. Most agriculture here depends on fertility locked up in the organic matter that accumulates during extended natural bush fallow intervals between cropping cycles.