The 2010/2011 season gave us the first strong evidence for what we are calling the modulated maize/velvet bean intercrop.
Background
Velvet beans (Mucuna pruriens) planted in the 2009/2010 season were left standing in the field after dry-season grazing. With the first significant rain of the 2010/2011 season, a large proportion of the velvet bean seed germinated spontaneously in the existing crop residues.
The system
Rather than clearing the field and starting again, we planted maize directly among the germinating velvet beans using the dibble stick. This required only light clearing of individual planting stations — the velvet bean provided a living mulch and weed suppression function from the start.
Weeding was confined entirely to the maize row. Between rows, the velvet bean was left to grow. When the maize reached approximately 30 cm, the velvet beans between rows were slashed back to ground level.
No compost or fertiliser was applied to this trial area.
What happened
The slashed velvet bean decomposed rapidly — the germinated seed carries concentrated nutrients from its cotyledons, and this combined with the root-fixed nitrogen produced a powerful nutrient pulse at exactly the right time for maize vegetative growth.
Some velvet beans survived the slashing. These grew up through the maize canopy, climbing the stalks and forming a dense canopy alongside the maize. The combination shaded out subsequent weed emergence completely.
Results
Final yield from this plot was approximately 7 tonnes/ha — achieved without any external input.
The field is now pre-loaded for the following season. Velvet bean residue on the surface, standing stems available for early germination, and excellent soil moisture from the dense canopy cover through harvest.
Tags: Intercropping · Maize · Mucuna pruriens · No-input · Soil health · Velvet bean