The dry bean is an important ﬁeld crop because of its high protein content and dietary beneﬁts.
Beans are a warm season legume being upright or bush type plants. Small ﬂowers are produced in clusters at various nodes on the stalks and can be either white or lavender in colour.
The ﬂowers are self-pollinating. Flowering continues for 2-3 weeks, so there can be a mixture of new pods, half developed pods and pods nearing full development.
The ﬁrst half of the growing period is vegative development and the latter half is reproduction. The crop matures in 85 to 120 days from planting. As the pods mature they change from green to light brown or tan. Each pod can contain 2-4 seeds. Yields can vary from 600kg per hectare up to 1,5 tonnes per hectare.
Generally they are planted early January to late February in the highveld and right through to mid-August in the low veld frost free areas. The soil temperature must be above 13°C for optimum germination results. Dry bean production requires a warm climate with temperatures between 18° C – 24° C. The maximum temperature during the ﬂowering period should not exceed 30° C as high temperatures will cause ﬂower drop and thus low pod set, resulting in depressed yields.
Beans require a minimum of 400mm to 500mm rain fall during its growing season but totals of 600mm to 650mm is considered ideal. Irrigation is also required where the crop is growing out of the rains and in winter production in the low veld area.
The critical growth stage requiring rainfall or irrigation is during ﬂowering and pod set. Irrigation should stop when roughly 25 percent of the bean pods have turned yellow.
The soil needs to be ploughed or ripped to a depth of 300mm then disced to get a good tilth, the soil needs to be ﬁrm at planting and a level seedbed prepared to ensure even germination. A level ﬁrm seed bed ensures good surface contact between the seed and soil. Planting depth of the seed should be 2,5cm to 4,5cm below the soil surface.
The optimum spacing between rows is 75cm. A spacing of 90cm is also used when agricultural machinery is set up for maize planting. Seed spacing in row is between 60mm to 75mm. Generally around 177 000 to 200 000 plants per hectare will give good results.
Beans will do best with a soil PH of 5,5 – 5,8. Beans are very sensitive to acidic soils. If the PH is not at these levels then apply lime as per the soil sample recommendations.
Beans can be planted into soils which have been well fertilised for previous crops though slight top ups at planting will be beneﬁcial.
A rate of 250kg per hectare of Compound ”D” drilled in with the planter, or broadcasted with a Vicon before the ﬁnal discing before planting. Calcium Sulphate (Gypsum) at 250kg per hectare as a top dressing just prior to ﬂowering will help with pod set. If a previous crops residue has been ploughed or disced in, then extra nitrogen will be needed to help composting or breaking down of the material.
This is very important in growing a dry bean crop. Bean plants compete poorly with weeds as they are low growing and do not over shadow weeds. Weeds that are not controlled will interfere with the harvesting and threshing of the crop.