The recommended sites for planting beans should include the following;
- Deep, fertile, well-drained and aerated, sandy loams or loamy soils.
- An optimum pH of 5.8 to 6.5 as beans is highly sensitive to acidic soils.
- Signs of soil fertility such as the presence of indicator plants like Guinea grass, commelina and the like.
- For steeply sloping areas, consider contour hedgerows and terraces along the contour to stabilize the soil and minimize the runoff.
During site selection, avoid the following;
- Waterlogged areas because beans don’t tolerate waterlogged places.
- Very sandy soils.
- Soils that are compacted (clay) and too alkaline.
It is essential to assess soil health before any soil management operations are implemented. Constraints such as soil acidity and soil nutrient deficiency can lead to significant reductions of crop yields. The soil pH and nutrients levels can be determined by conventional soil analysis in addition to observation methods of crops growing in the field.
Soil testing is an essential crop management tool that enables one to;
- Determine acidity and alkalinity levels of soil (pH).
- Identify any soil nutrient deficiencies.
- Estimate optimum fertilizer requirements for target yields.
- Estimate the optimum cost of fertilizer needed and the returns.
Timing of land preparation
- The timing of land preparation is extremely important.
- Land preparation should begin either at the end of the harvesting period or at least 3 weeks (21 days) before planting to allow breakdown of organic matter.
- Land should be ploughed at least twice in some cases followed with harrowing to obtain a fine seedbed.
- Where the field has a known history of bean pests such as pod borers, bean fly and beetles, complement ploughing with harrowing to kill the surviving eggs, pupae and adult pests.
- If the site is very bushy, first clear land by slashing down all plant parts and leave them on the ground, or plough in the plant residues using appropriate equipment.
- This will help soil to conserve moisture; improve the water-retention capacity, water-infiltration capacity and increase soil fertility.
- If the field was previously covered with weeds like Amaranthus spp, which produce a lot of seeds, then the land needs to be prepared early in the season.
- This will encourage most of the weed seeds to germinate as soon as the soil gets any moisture.
- The field can then be lightly tilled down or sprayed with non-selective herbicides (glyphosates) before beans are planted; very shallow cultivation is needed, only along the topsoil, to remove the germinating weeds.