- TYPES OF BEANS
Figure 1 and 2: A good crop of edible beans
Source: groweralliance Source: hechoenmexicob2b.
There are a number of different types of beans grown in Southern Africa, the main ones being the following:
EDIBLE BEANS
These are grown to produce immature edible pods eaten as ‘green beans’ and for the sale of mature beans which are harvested, dried and marketed. There are two main types of edible beans: The dwarf beans also known as French Beans, and the tall beans called Scarlet Runner Beans.
VELVET BEANS
These are grown to produce mature beans which are dried and sold for human consumption. These beans are also used for cattle feed and the stalks or haulms as they are called can be made into hay. When the plant is just reaching maturity, before the pods have ripened, the crop can be cut for silage or ploughed in as a green manure. Being a legume this crop makes a very valuable green manure adding nutrients to the soil, particularly nitrogen, and improving the soil structure. Using Velvet Beans for the purpose of green manuring is a common practice in Southern Africa.
DOLICHOS BEANS
These are very similar to Velvet Beans and are grown for the same purpose; for sale as dried bean cattle feed or ploughed in as a green manure.
CASTOR BEANS
These are grown for the production of castor oil, which has medicinal and lubricating qualities.
JACK BEANS
These are grown manily for green manuring. The plant produces a large bulk of green matter making it very suitable for this purpose. The beans themselves can be fed to cattle in small quantities but can be poisonous to cattle and sheep and are best avoided. The cultivation of all the types of beans is very similar so it will be sufficient to describe the cultivation of the edible beans only.
- CULTIVATION OF THE EDIBLE BEAN
This bean is known as Phaslolus vulgaris and is grown in many parts of the world. It is thought to have originated in Mexico at about the same time as maize and was taken to Europe in the 16th Century by the Spaniards and Portuguese, who also took it to Africa. It reached England in 1594. Many hundreds of varieties have been produced and new ones are introduced each year. Varieties are divided into:
Dwarf or bush varieties which do not require support and are early maturing. These are the French Beans and the type grown on farms.
Climbing or pole varieties which require support with sticks are slower to mature and produce. They have a longer bearing season. These beans grow to 2 ‐ 3 metres high, are heavier yielders and are the Scarlet Runners grown by market gardeners and not grown as a field crop on farms.
Figure 3 and 4: A Dwarf or bush type variety (left) and a climbing variety (right)
Source: talesfromthemountainside.blogspot Source: backyardorganicvegetables.blogspot.
Two common varieties of the dwarf variety grown in Southern Africa are Contender and Class Act. Two runner type varieties are Lazy Housewife and Witsa.
CLIMATE AND SOILS
Beans can be grown on most soil types from sandy loams to heavy clay provided that drainage is good as they dislike waterlogged conditions. They do better on the heavier and more fertile soils and prefer a pH which is slightly acidic to neutral – 5.3 to 6.
Beans can be grown either as a summer crop or in winter under irrigation. Beans do well when grown during the winter in the Lowveld. Optimum temperatures for growth are between 15°C
and 21°C. Temperatures below 12°C and temperatures above 30°C affect fruit set and quality. They are very sensitive to frost and any moderate frost will kill off the crop completely.
Beans should be planted into a well‐prepared level seedbed free from lumps and level so that no water can be left standing in hollows. The soil surface should be loose because when beans germinate they push their cotyledons through the soil surface and for this reason soils which form a
surface crust should be avoided.
FERTILISER
The soil should be sampled and sent for analysis. In most cases the supply of phosphate and potash should be adequate. Although beans are a legume and produce their own nitrogen from root nodules it has been found that nodulation is poor until the plant has flowered. Due to this it is best to apply 250 kg/ha – 500 kg/ha of 2:3:4(30) at planting depending on soil fertility. Topdress at 3 weeks of age with 200 kg/ha – 250 kg/ha of LAN.
SOWING AND PLANT SPACINGS
This can be done by hard or by using a maize planter. Beans are sown in rows 450 mm – 600 mm apart and with a spacing of 40 mm – 70 mm between seeds in the row. Generally the more closely the crop is planted the better the results and the higher the yield. Seeding rate for beans is between 60 kg/ha – 100 kg/ha. Seed should be dressed with an insecticide to prevent damage by the bean stem maggot.
Figure 5: Plant Spacings
300 – 450 mm between rows 40 – 70 mm in the rows
60 – 100 kg/ha of seed depending on size
IRRIGATION
The root zone should be brought up to field capacity at planting and assuming that this requires 100 mm water then 4 later applications of 65 mm at intervals of 24 ‐ 27 days should be sufficient. The total water requirements of the crop would be 325 – 380 mm. Lighter applications of water at shorter intervals should be avoided.
Planting times vary according to the areas to be planted. In the cooler areas the ideal times for planting are between October – November and January. The warm areas ideal planting time is September – October and January – February. The hot areas ideal planting times are March – August. When grown as a late summer crop in the highveld the planting date should be timed so that the crop will not be damaged by late June and July frosts.
DISEASES
Beans suffer from a number of fungal diseases and bacterial blight particularly when grown in the summer or under overhead irrigation. These diseases can generally be avoided by using disease‐free seed and having a gap of at least 3 years between crops grown on the same land.
PESTS
Common pests of beans are Eelworms, Bean Stem Maggot, American Bollworms and Mites. Eelworms can be avoided by using at least a 3 year rotation and Bean Stem Maggot by using a seed dressing and other pests by using insecticides when required.
Figure 5 and 6: Examples of diseases, Bacterial Blight (left) and Rust (right)
Source: insectimages. Source:greeningofgavin
Figure 7 and 8: Examples of pests, American Bollworm (left) and a Brown Mite (right)
Source: nbaii.res Source: bugguide
HARVESTING
It is important to exercise some judgement during harvest in order to keep seed losses low and quality high. Losses resulting from harvesting too soon result in lower yields and seed of poor quality. If harvest is delayed too long yield loss from shattering may occur.
The crop should be reaped when most of the pods have turned yellow but before they have become completely dry. Seeds should be firm and well developed in the pod and should have just begun to break free from the inside of the pod.
Bush cultivars set their seed over a period of 2 to 3 weeks but it is usual to harvest the whole crop in one operation. Plants are pulled or cut off at ground level and laid in windrows until dry which is best done early in the morning to avoid shattering. Once dry, the beans are either threshed in the field or moved to cover.
Edible beans can also be harvested as ‘green beans’. The pods should be crisp, firm and show no evidence of bulging. Any bulging will indicate an overripe bean pod. When the pod is broken in two it should make a snapping sound.
THRESHING
Constant care must be taken to avoid rough handling of seed beans for market. This should be a matter of concern to growers and cleaners alike since seed‐coat damage is compounded with each cleaning operation, which results in seriously impaired quality. As an example, dropping a bag of bean seed onto a concrete floor from a height of 1 metre can reduce germination from 90% to 60%.
Beans may be threshed by hand using a flail either in the field or on a threshing floor or be pressed out by a rubber‐tyred tractor. Special seed‐bean shellers and grain shellers damage too many of the beans to be satisfactory.
YIELDS
1 – 25 tons/ha
Figure 9 and 10: A team harvesting beans (left) and beans that have been harvested and placed in crates (right)
Source: tempelfarmsorganics.blogspot Source: littleridgefarmmembers.blogspot
Figure 11 and 12: Threshing beans by hand once they have dried out (left) and using an old mechanical thresher (right)
Source: ghana.usaid Source: northbranchfarm‐monroe.blogspot
