DRY BEANS) (Phaseolus sp)
In Kenya beans are the most important pulse. They rank second to maize in importance as a food crops. The crop provides a cheap source of protein
Beans grow best in altitude above 600m.a.s.l, below this, high temperatures causes’ flower and pod abscission causing poor fruit set and hence reduced yield. There are also high incidences of diseases like; bean rust, and bean anthracnose below this altitude. Altitude between 900-2100 is most suitable but can be grown up to 2700m.a.s.l. Beyond this altitude there is the problem of frost damage because it’s not resistant.
Beans require a minimum of 400 to 500 mm of rain during the growing season. Excessive rainfall during flowering causes flower drop and increased disease incidences. Medium rainfall is thus required during flowering and pod set. Dry weather is required during harvesting.
Best growth is obtained in soils that are well drained and high in organic matter. Beans grow well in soils with a depth of at least 90 cm. Sandy soils have lower fertility and higher incidences of nematode damage than other soil types. The optimum soil pH is 6.0 to 7.0. The crop is very sensitive to acidic soils. Below pH 4.5, nitrogen fixation is impaired.
The bean crop thrives in a warm climate. It grows optimally at temperatures of 18 to 24 °C. The maximum temperature during flowering should not exceed 30 °C. High temperatures during the flowering stage lead to abscission of flowers and a low pod set, resulting in yield loss. Day temperatures below 20 °C will delay maturity and seed formation causing pods to mature empty. The crop is very sensitive to frost minimum temperatures should not go below 13 °C.