By Umar Nsubuga
Soils
French beans can grow in a wide range of soil types, ranging from sandy, and loam to clay. They, however, grow best on friable (easily crumbled), silty loam to heavy clay soils which are well-drained and high in organic matter.
Henry Sekyewa, an agronomist says the optimum soil pH should be 6.5 to 7.5, but beans can tolerate a low pH of up to 4.5.
He says below pH 4.5, plant growth is impaired through the limitation of the development of the Rhizobium bacteria that are responsible for the nitrogen fixation in the galls formed on the bean roots.
It’s advisable to carry out a soil test before planting. Being members of the legume family, they have nitrogen-fixing bacteria in their root nodules and these need lots of air in the soil, so the structure must be loose and open.
Fairly light soil to which plenty of organic material has been added would be ideal. Too much water-logging encourages pests and diseases and should be avoided.
According to Gideon Zakke, another agronomist at a temperature ranging between 200 C and 290 C, the crop matures faster. However, it grows much slower in colder environments.
French beans can generally be grown successfully across Uganda.
Land preparation
Isaac Malinga, a French beans farmer says French beans are sown directly into the seed bed. The land should be ploughed and harrowed properly just before planting. The field should be allowed to rest/cool off for at least two weeks after ploughing before the planting is done.
Planting
With irrigation, Malinga says French beans can be grown all year round, but the main export season is from October to May. All bushes around the garden should be cleared before planting.
If there is plant debris in the freshly prepared garden, wait for about 3 days after ploughing before planting so that the debris dries up. This reduces incidences of pests and diseases.
Spacing
Single rows measuring 30cm x 15cm (1 seed per hole) or double rows 60cm x 30cm may be used. Four lines should be planted across a row (bed) at a space of 20-25cm apart.
Seeds should be planted in a line at a space of 8-10cm between them. Seeds should be planted 1-2inches deep.
The spacing will depend on the variety, soil fertility, water availability as well as climate. It is advisable to plant in blocks of about 4 rows separated by a path of about 50cm.
The seed rate required is, 25-60kg/ha (10-24kg/acre) of certified seeds depending on the variety.
