The Red Speckled beans commonly known as the sugar bean is a legume. It is grown for its seed, which is eaten as a vegetable. It has a high soluble fibre content. Soluble fibre absorbs water in the stomach forming a gel that slows down the absorption of the bean’s carbohydrates.
Sugar bean (common bean) is a grain legume which is very nutritious and rich in protein.
The leaves, green pods, and young and mature seeds are edible. The crop residues are good to feed livestock or form a good basis for compost manure. There is a ready market for sugar beans.
Together with bacteria, sugar bean forms root nodules. These bacteria are called rhizobia.
In the root nodules, the bacteria can fix nitrogen from the air into a form that sugar beans can use for growth. Part of the fixed nitrogen is used to make protein in the grains, but some of the nitrogen is also left behind through falling leaves and roots. The nitrogen that is left behind improves soil fertility. This makes sugar bean a good crop to grow as an intercrop or in rotation with other crops because these other crops then also benefit from nitrogen.
However, sugar bean does not fix nitrogen as well as cowpea. To get a good sugar bean yield you can inoculate bean seed with rhizobium inoculant or apply initial N fertilizer at planting.
Step 1: Land selection and preparation
• Select fertile to moderately fertile land with no water logging. Sugar bean does not
tolerate acidic soils.
• Think about the rotation scheme for the field you want to plant. To prevent diseases, do
not plant beans in the same field you used for beans last season.
• Clear all vegetation and prepare the field manually with a hoe, or use animal power or
a tractor. You can plant sugar beans on ridges or on a flat seedbed. Planting on ridges
helps prevent waterlogging, which damages the sugar bean plants.
• Well-prepared land ensures good germination and reduces weed infestation.
Select a good bean variety which suits your agroecological zone. Also, pay attention to
the maturity period. Some varieties have a relatively short maturity period and are suitable for areas with low rainfall, or when planted late in the season. Late-maturing varieties are
less suitable for drier environments, but often produce higher grain and biomass yields, fix
more nitrogen and contribute more to soil fertility than early-maturing varieties.
Variety Grain characteristics Attainable grain
period (days) Seed rate
Bonus White with purple speckles 2000-3000
Cardinal Purple with white spots 2500-3000 75-100 100 kg/ha
Speckled Ice White with red speckles 2500 – 4000
SC Bounty Speckled 2000-3000 115 80-100 kg/ha
Use only high-quality seeds for planting.
• Sort out good seeds to ensure that they are free from insects, disease infestation and weed seeds. Do not use damaged or wrinkled seeds or seeds with holes.
• Do a germination test at least 10 days before the time of planting. Plant 50 seeds. If at least 40 emerge, the seed is good for planting. If 30-40 emerge, plant more seeds than recommended. Get new seeds if less than 30 seeds emerge.
Inoculation with rhizobia can help sugar bean to form nodules and fix nitrogen. Each
legume crop needs a different type of rhizobium bacteria, so always check you have the
right inoculant for sugar bean.
How to inoculate sugar bean with rhizobia
- Spread 100 kg of sugar bean seed on a clean plastic sheet or in a large container.
- Mix 100 g of inoculant and 1 litre of water in a clean bucket.
- Add 50 grams of sugar to the solution. The sugar acts as an adhesive between
the seed and the inoculant.
- Stir the solution for 30 seconds.
- Sprinkle the inoculant mix onto the seed.
- As you sprinkle the inoculant onto the seed, turn the seed gently to ensure that all
seeds are coated with the inoculant. The coated seeds should look shiny and wet.
- Plant immediately after inoculation and protect the inoculated seed from direct
sunlight by covering the container with paper, cloth or a gunny bag.
- Sow the seeds in moist soil and cover them immediately afterwards to protect the
rhizobia from sunlight.
• The right inoculant must be used with the right legume. You should not apply, for
instance, a soybean inoculant on sugar bean seed.
• Inoculant contains living organisms that must be protected from heat and sun.
Therefore always store the package in a cool place away from direct sunlight (for
example, in a clay pot in the coolest place in the house).
• Inoculants lose their effectiveness when stored in an open package. Always store
inoculants in their original package and use them quickly after opening the bag.
• Seeds should be coated with inoculant just before planting.
• Nodulation will fail if the inoculated seed is exposed to the sun for any length of time or is sown into dry soil and left for several days before irrigation/rain.
• Do not use the inoculant after its sell-by date, as the inoculant may then not be effective
• Sugar bean needs phosphorus at planting. Good fertilizer types that supply phosphorus for sugar beans are SSP or compound L.
• Although sugar bean can fix nitrogen, it often benefits from a small starter dose of nitrogen from fertilizer. Fertilizer types that supply both phosphorus and nitrogen are compound L, compound D or NPK.
• Make a furrow of 5-7 cm deep. You will also use this furrow to plant sugar beans. Place the fertilizer in the furrow and cover it with 2 cm of soil. If you don’t cover the fertilizer
with soil, the fertilizer will ‘burn’ the seed.
• Use the rates given in the table below for mono-cropped beans. You can use a teaspoon or soda bottle cap to measure the amount of fertilizer and apply it in the furrows, according to the distances in the table.
• When manure has been applied recently, rates can be reduced.
Fertilizer type Rate (kg/ha) Row spacing: 20/30 cm.
In the furrow, spread 1
Teaspoon Soda bottle-cap
SSP 225 Every 85 cm Every 55 cm
Compound L/Compound D/NPK 150 Every 125 cm Every 80 cm
Plant when the soil is moist. Planting in rows has many advantages; you use the correct
plant density, weeding is easier and harvesting takes less time.
Planting beans in a mono-culture
• Plant in rows which are 20-30 cm apart. Within a row, plant seeds 5-7 cm apart (1
seed per stand).
• Plant seeds at a depth of about 5 cm.
• Fill gaps one to two weeks after planting when plants have emerged.
Planting beans in a mixed culture
Beans can be intercropped with maize. Beans do not grow very well when shaded. To reduce the shading effect, multiple rows of beans can be planted after 2 rows of a cereal
What is the best time to plant sugar beans?
According to Mbele, clean lands and good timing are crucial when planting sugar beans. The soil should also be well-drained. The optimal planting window for his area is from 24 November to 20 December. When preparing lands, he avoids ripping, as this allows too many weeds to germinate.
How long do sugar beans take to grow?
|Seed type||Sugar beans|
|Maturity||85 – 95 days|
|Adaptation||KZN and Lowveld (late plantings elsewhere)|
In which season do we grow beans in Zimbabwe?
Planting dates in Zimbabwe range from October to mid-January in areas where frost occurs. In frost-free areas, March and April are the best for planting beans. It is recommended that those beans be planted on soils which have been well fertilised previously.