Step-by-step guide to growing beans successfully

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Damaris Awino aka Nyasuba tends to her climbing beans at her home in Katito in a photo taken on January 10, 2017. [Denish Ochieng, Standard]

The common bean (Phaseolus vulgaris L.) is the world’s most important legume for human consumption, according to Katungi et al 2010. Beans are a source of protein that makes the Kenyan population highly dependent on them. The market for beans is overwhelming and depending on the quality and type of beans, prices per 90 kg bag of beans range between 7,000 and 12,000 shillings. Pricing is dynamic and influenced by seasons and varieties. Some varieties that are not grown by many farmers may fetch a higher price due to the difference between supply and demand.

Improved beans

There are many varieties of beans. Between 2008 and 2018, around 33 new varieties were released by research organizations such as Kenya Agriculture and Livestock Research Organization (Kalro), Egerton University and Kenya Seed Company.

Kalro bean researcher David Karanja, explains that the new varieties are improved beans that are more resistant to climate change, are hardy and contain trace elements like zinc, which is important for human growth and physical condition.

“How many of these new varieties are known to change agents and farmers? Mr. Karanja poses. Her question indicates that there is a great need to educate farmers on new varieties for them to adopt climate-smart and resilient agriculture. Some of the 33 new bean varieties include Angaza, Faida and Nyota.

Bean eating behavior

Bean eating behavior also varies from place to place. Some communities eat the leaves as vegetables, others eat green beans as in the case of green beans and green beans and the most common is the dry grain. Leftover bean stalks are also excellent fodder for livestock and some communities burn them to make food additives called munyu by the Luhya community.

Bean agronomy

Farmers must start by planting good quality seed for good crop establishment. The original seed must have the following characteristics:

  • A variety (a color or pattern) – Farmers who grow from their own seed tend to mix different varieties through seed exchanges with other farmers. This does not work in their favor as different varieties have different growth habits, so crop interaction is not optimized for maximum production. Avoid mixing varieties not only for beans but also for other crops.
  • Viable (ability to germinate) – This can be tested by growing 100 seeds before planting and counting those that germinate. If out of 100 only 50 germinate, that seed has a germination percentage of 50%. This means that if you decide to use it, half of your farm will have no harvest. This increases production costs as farmers are forced to practice spacing. Always go for seeds with a high germination percentage.
  • Free from seed-borne diseases and pests. To do this, always buy seeds that are certified with a stamp/sticker from the Kenya Plant Health Inspection Service (Kephis), stating that they are free from pests and diseases, as some cannot be seen with the naked eye .
  • Free of inert materials. Do not plant seeds contaminated with stones or leaves. Inert materials change seed weight and can introduce other contaminants.
  • Not shriveled, moldy or cracked. Cracked seeds can miss the most important part which is the essential embryo for growth. Moldy and shriveled seeds are indications of fungal contamination that can lead to crop failure early on.
  • Not rotten or discolored

seed rate

The recommended seeding rate is 40-50 kg/ha, which translates to 16-30 kg per acre. When planting, farmers should observe the number of seeds per mound. Sow at least two seeds per mound. The planting depth is four to five centimeters. Do not plant beyond five centimeters as the sprout may struggle to emerge, resulting in a poor harvest.

Grain spacing

Bean spacing is influenced by a number of factors such as the variety and the type of growing system adopted. Beans can be grown for green bean production as string beans or beans for dry grain. You can also adopt different cropping systems like monoculture or intercropping. When grown as a sole single crop, spacing is 50cm by 10cm per bean. Banana intercropping has a spacing of 45 cm by 20 cm. Different intercrops have different spacings.

Bean fertility and crop nutrition

Before deciding on any crop nutrition activity for your bean crop, it is always advisable to do a soil test. This is because beans have the ability to fix nitrogen in the soil, hence the need to follow proper crop nutrition guidelines. When planting, use well-rotted manure and DAP. DAP helps in root formation, which is essential for growing beans. Consider topdressing before the crop blooms. After flowering, no activity should take place until pods form to avoid flower drop.

weeding

Up to 50% crop loss can occur due to uncontrolled weeds. The first weeding should be done two weeks after emergence. Weed early before weeds get bigger and compete with your bean crop. The second weeding should be done before flowering. After flowering, do not weed but pull weeds by hand if necessary to avoid flower abortion and disease attack.

Main bean diseases and pests

Beans are susceptible to pests and diseases and can easily be wiped out if not properly cared for at any stage of growth. It is therefore recommended to take care of the grains at all stages. Scout your bean crop weekly to assess performance and identify pests or diseases. This helps you quickly identify pest and disease incidences for rapid management. This is before economic injury levels are reached. Economic injury levels are levels of infestation or infection that make no commercial sense to apply control or management methods, the crop will have been lost. Always choose preventive care and measures rather than reactive. Early intervention will save your investment in growing beans.

Anthracnose disease

Anthracnose is a fungal disease mainly spread by infected seeds. Once the crop is attacked by diseases, symptoms appear on the stem, leaves and pods. Control is difficult. Do not use seeds from infected plants. Use certified clean seed.

Bean common mosaic virus

Symptoms appear as an irregular mosaic pattern of light yellow and green or a band of dark green along the veins on an otherwise green leaf. The foliage can wrinkle and distort, often causing the leaf to curl. Grow tolerant varieties from certified seed. Control aphids if the variety being grown is not tolerant.

Fusarium root rot

The causative fungus Fusarium grows best in warm temperatures. Solarization kills the fungus by raising the temperature to a level of extreme heat where no fungus can survive. Plant tolerant varieties. Practice crop rotation (not with Irish potatoes) and treat planting seeds with a fungicide like Apron Star and Murtano.

leaf rust

It is caused by a fungus that attacks the leaves, stems and pods of bean plants. Rust spots have a reddish-brown powdery substance. If not controlled in time, excessive infection eventually leads to the death of plants or parts of plants, causing huge losses. Plant resistant varieties. Rotate with non-host plants like cereals.

Maintain field hygiene and in case of infection, spray fungicides alternating the active ingredient (with sticker).

Powdery mildew

Symptoms include twisted, curled, or distorted leaves with a whitish substance. Apply sulfur fungicides preventively rather than curatively. Start the crop on fertilized soil that is well moist so that the crop is strong. Do not perform overhead irrigation. Do not grow under shade.

Bean pests

cutworm

Apply an insecticide in the late afternoon for better control. A mulch of neem leaves is useful against cutworms.

Bean Maggot Control

Early planting avoids major damage that occurs later. Earth/replenish the soil around the plants to cover the roots two to three weeks after emergence.

Chemical control using various systemic insecticides can be adopted.

Thrips Control

Adopt different cultural control methods like timely weeding, use of neem oil and botanical control like BotaniGard ES.

Aphid control

Cut and compost stems containing aphid clusters. Dusting the plants with flour constipates the pests. Do the weeding early enough. When the problem worsens, chemicals can also be used.

Whitefly control

Remove weeds that hide pests, maintain field hygiene after weeding and using chemicals.

Bean Pod Stage Pests

Pod borers

Most pod borers cause damage in the caterpillar stage, such as bollworm larva, Heliothis larva. Always destroy plant debris from the previous crop by using it in a compost pit or as animal feed. This ensures that the eggs laid there will not move on to the next growth cycle. Use products of plant origin, such as neem, derris, pyrethrum and chili (with the addition of soap).

sucking insects

Plant sucking bugs occur from the vegetative stage to the beginning of pod formation. Pests can be controlled by planting repellent plants such as “dhania” parsley and onions in bean plants.

Synthetic pyrethroids are effective, but also kill natural enemies. Use plant-derived products like in pod borers.

When using chemicals, do not repeatedly use one type of insecticide to avoid resistance. DO NOT mix insecticides and foliar fertilizers in a spray tank.

[The writer is FarmKenya Initiative project leader. BSc Agriculture, Egerton, MSc AICM, UoN]

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