Local names in Kenya (Mahindi na Maharagwe, Oduma/Bando gi Oganda, Madumwa na Managanda)
Smallholder farmers commonly use maize and bean intercropping to increase soil nitrogen and enhance agricultural productivity. If intercropped, the choice of the legume intercrop should be based on presence of soil and climatic conditions that meet the requirements of both maize and the legume of choice. Maize-legume systems usually produce less maize than maize monoculture but provide higher overall economic returns. Higher land productivity makes maize-legume systems especially suitable for smallholders. Intercropping maize with legumes also increases land utilization and reduces pests and diseases.
Select a site away from shade to allow for all-day sunshine and at least 10 meters away from roads to prevent the crop dust or vehicle fumes.
Other site selection requirements is defined by ecological requirements for maize.
Avoid sites that are prone to waterlogging, or with steep slopes.
The Ecological requirements are as follows:
Maize/bean intercrop can be grown at altitudes of 1000–2000 m.a.s.l.
Soil type and conditions
Soil conditions should be as for maize; deep, well drained, fertile alluvial or loam soils with good water holding capacity and high organic matter (5% or more). Optimal soil pH is between 5.5 and 6.0.
The temperatures should be 15-27oC
The rainfall should be 500-1500 mm per growing period.
Prepare the land early to allow stubble enough time to rot.
Recommendations for land preparation:
(1) Consider minimum tillage to conserve soil, water and nutrients, and to reduce cost and workload. Slash all vegetative cover.
(2) Ploughing can be done using chisel ploughs, hand hoes or oxen drawn implements to aerate the soil but avoid excessive soil disturbance as this destroys soil structure and may lead to loss of soil organic matter.
(3) In gentle to moderately sloping fields, use contour farming techniques. This requires setting out of contour lines and planting soil conservation crops (eg. Vetiver) along the contour lines. Land preparation activities and planting is done parallel to these contour lines.
- Farmer saved seeds are alternatives where certified seeds are not available
- Planting materials should be well-adapted to emerging local climatic and environmental conditions
Common planting materials include certified seeds and farmer saved seeds. Certified seeds are produced by registered seed companies and should be bought from reputable agro-dealers.
In selecting maize seeds, a choice can be made between Hybrid varieties and Open Pollinated Varieties (OPVs). Hybrid varieties are potentially higher producing but are not suited for seed saving (propriety rights, genetic variability). Farmer saved seeds are alternatives where certified seeds are not available or considered too expensive. The selection process for seed saving should include observing growth and tolerance to adverse conditions.
Damaged or wrinkled seeds, and seeds with insect or disease damage should not be used. Ensure that saved seeds are free of weed seeds.
For beans, nutritional value, and market and customer preferences will influence the demand for certain varieties. New bean varieties with higher iron and zinc levels (eg. Nyota) should be promoted as they are important to strengthen the human immune system.
The website of Seed Sector Platform Kenya (www.seedsectorplatformkenya.com) gives a good overview of available seed varieties.
Plant using appropriate tools such as rippers, jab planters, dibbler; or use oxen or tractor drawn equipment such as no-till planters.
Plant at the onset of rains at a spacing recommended.Early planting enables the crop to take advantage of nitrogen flush and adequate soil moisture.
Conduct germination test before planting.
Plant parallel to the contour lines, especially in sloping fields. Minimum tillage mechanical planting (direct seeding) is preferable to maintain parallel planting lines.
Recommended plant spacing:
Intercropping with single rows of beans:
Maize spacing is 75 x 25/30 cm with 2 seeds per planting hole. Beans are planted in a row mid-way between the maize rows and 10-15 cm apart in the row, with 2-3 seeds per planting hole.
Intercropping with double rows of beans:
Maize spacing is 90 x 25/30 cm with 2 seeds per planting hole. The two rows of beans are 30 cm apart and 30 cm from the maize rows and 10-15 cm apart in the bean rows, with 2-3 seeds per planting hole.
Maize and beans intercrop
The negative shading effect from the maize on beans can be reduced by alternating planting of two or more rows of maize (at pure stand spacing) with two or more rows of beans. This will also improve airflow through the two crops. Orientation of the planting rows in an east – west direction, if possible, will give the beans better exposure to sunlight.
Fill gaps one to two weeks after planting when plants have emerged.
Maize yields are negatively affected by drought periods. Soils with good moisture holding capacity, or the use of supplementary irrigation, will improve yields.
Soil and water conservation methods and minimum tillage techniques, including sub-soiling (ripping) will result in increased organic matter content of the soil, and improve the water-holding capacity. The use of mulch, especially in early growth stages, will reduce evaporation from the soil.
Irrigation is an essential climate change adaptation practice under dry conditions but must observe efficient water-use and wise application to avoid nutrient leaching and waterlogging. Adopt more water efficient micro-irrigation methods such as drip irrigation where water is applied directly to the root zone. This may be especially suitable for the bean crop, as the use of sprinkler irrigation may cause diseases.
Irrigation should be done early in the morning or late in the evening, or even at night to avoid excessive evaporation and possible plant damage.
General practice for maize is:
1st weeding 3-4 weeks after germination and 2nd weeding at “knee-high” stage (30 to 45 cm plant height). This is 6-7 weeks after planting.
Additional weeding, until the plant canopy is closed, can be beneficial.
Practice for beans:
1st weeding is done 2 weeks after emergence
2nd weeding is done just before flowering
Uprooted weeds should be left between the plant rows to act as mulch unless they are already in seed. Even more beneficial for soil biology and soil structure is to chop weeds at ground level and leave the roots to decompose in the soil.
Test soils before planting to guide application rates of manure and fertilizer.
Intercropping maize crop with bean crop (leguminous species) increases nitrogen availability for the maize crop.
Improve and maintain good soil biology and fertility for improved production and income by practicing conservation farming approaches such as minimum soil disturbance, permanent soil cover, and crop rotation, as well as soil conservation measures.
The current MoA recommendation for maize/bean intercrop is the same as for pure stand maize:
At planting: Apply 50 kg/acre of NPK blend. Baraka Blend also contains macro (Ca, Mg) and micro-nutrients (B, Mn, S). In hand planting, place one bottle cap of the planting fertilizer in the planting hole and mix with the soil before placing the seed. In mechanical planting, fertilizer is placed first in the planting furrow before the seeds.
Compost (well-decomposed manure) can be applied (two hands full) in the planting hole and mixed with the soil before placing the seed. NPK blend is added to the compost at half the rate (25 kg/acre).
At top dressing: A single application of 50 kg/acre of a CAN fertilizer (Baraka top dress) is applied when the maize crop is about 30 cm high. The fertilizer is placed in a ring around the maize stem (5 cm away from the stem).
Fertilizer is only applied to the maize rows.
Practice conservation farming approaches like minimum soil disturbance, permanent soil cover, and crop rotation, and implement soil conservation measures.
Gapping and thinning of beans and maize should be done 14 days after emergence. It is recommended to thin to 2 plants per hill in a spacing of 75 x 50 cm or 1 plant per hill in a spacing of 75 x 25 cm for maize and 2 to 3 plants for beans.
Well managed maize and beans intercrop
For maize crop, major pests include Fall Armyworm, Armyworm (Spodoptera exempta), maize stalk borer (Busseola fusca), termites, cutworms, leaf miner, moths, beetles, thrips, grasshopper, rodents (rats and mice), weevils (Sytophylus zeameis) and Larger grain borer (Prostephanus truncatus).
For Beans, major pests include African bollworm (Heliothis armigera), bean aphid (Aphis fabae), bean fly (Ophiomyia spp), flower thrips (Taeniothrips siostedti) and leaf miner.
Control of these pests is as described under maize and bean monocrop.
At maturity bean plants and pods have dried up and turned yellow or brown.
For maize, the stage of maturity is determined by yellowing of the leaves, yellow dry papery husks, and hard grains with a glossy surface.
Beans are harvested first before pods begin to shatter.Harvesting of maize follows 10 -15 days after physiological maturity.
Beans are harvested by cutting or uprooting the whole plant while maize is harvested by cutting and stalking to enhance drying and the de-husking
Dry maize and beans to the required moisture content of 13-14% before storage.
Beans are dried, threshed and winnowed to remove chaff and dust. Re-drying of beans is done to attain storage moisture content level. The beans are then sorted and bagged for storage.
For maize, after the initial drying in the field, cobs are removed from the stalks and transported to the homestead or other collection point for shelling.
After shelling, the grains should be winnowed to remove dust and chaff. If necessary, the grains can be further dried in the sun. The grains should be spread out on clean tarpaulins, not on soil, to avoid aflatoxin infection.
Control weevils, fungal infections e.g aflatoxin and grain borers by re-drying the maize to 13-14% moisture before bagging or storing.
Dried maize and beans are stored in airtight bags or metallic silos
Storage of clean, dry grains in airtight bags (hermetic bags) or metallic silos is recommended. Storage of grains in sisal or jute bags indoors will require fumigation or the use of insecticides.
Stored grain must be kept dry, and bags placed on pallets or raised platform. The storage space must be protected from rodents and dust.