iCowApp

Credits: Biovision-Infonet

Scientific Name: Zea mays

Order / Family: Cyperales: Poaceae (Graminae)

Local Names: Mahindi (Swahili); Mbembe (Kikuyu)

Pests & Diseases: African armyworm, African bollworm , African maize stalkborer, Angumois grain moth, Aphids, Common rust, Common smut, Couch grass, Cutworms, Ear rots, Fall armyworm, Grasshoppers, Grey leaf spot, Head smut, Larger grain borer (LGB), Maize ladybird beetle, Maize leafhoppers, Maize lethal necrosis (MLN), Maize plant hopper, Maize streak virus, Northern leaf blight, Purple witchweed, Satintail, Southern leaf blight, Southern rust, Spider mites, Spotted stemborer, Termites, White grubs

Other pests: Sedges

Geographical Distribution in Africa

General Information and Agronomic Aspects

Maize is the most important cereal crop in sub-Saharan Africa. It is a staple food for an estimated 50% of the population. It is an important source of carbohydrate, protein, iron, vitamin B, and minerals. Africans consume maize in a wide variety of ways (maize meal, porridges, pastes and beer). Green maize, fresh on the cob, is eaten baked, roasted or boiled. Every part of the maize plant has economic value: the grain, leaves, stalk, tassel, and cob can all be used to produce a large variety of food and non-food products. In sub-Saharan Africa maize is mostly grown by small-scale farmers, generally for subsistence as part of mixed agricultural systems. The systems often lack inputs such as fertiliser, improved seed, irrigation, and labour.  According to FAO data, Africa produced 7.4% of the 1, 135 million tonnes produced worldwide in 40 million hectares in 2017 (FAOSTAT, 2017). 

Maize is also an important livestock feed both as silage and as crop residue, grain and is also used industrially for starch and oil extraction.  

Climate conditions, soil and water management

Maize is a versatile crop, growing across a range of agro-ecological zones. With its large number of varieties differing in period to maturity, maize has a wide range of tolerance to temperature conditions. It is essentially a crop of warm regions where moisture is adequate. The crop requires an average daily temperature of at least 20degC for adequate growth and development. Optimum temperature for good yields is around 30degC. The time of flowering is influenced by photoperiod and temperature. Maize is considered to be a quantitative short-day plant (short days can induce premature flowering). It is grown mainly from 50degN to 40degS and from sea level up to about 3000 m altitude at the equator. At higher latitudes, up to 58degN, it can be grown for silage.

 Maize is especially sensitive to moisture stress around the time of tasselling and cob formation. It also needs optimum moisture conditions at the time of planting. In the tropics it does best with 600 – 900 mm of rain during the growing season. Maize can be grown on many soil types, but performs best on well-drained, well-aerated, deep soils containing adequate organic matter and well supplied with available nutrients. The high yield of maize is a heavy drain on soil nutrients. Maize is often used as a pioneer crop, because of the high physical and chemical demands it makes to the soil. Maize can be grown on soils with a pH from 5 – 8, but 5.5 – 7 is optimal. It belongs to the group of crops that is considered to be sensitive to salinity. Since a young crop leaves much of the ground uncovered, soil erosion and water losses can be severe and attention should be paid to adequate soil and water conservation measures.

• Local seed. Low to medium yields, usually well sheathed and so more resistant to weevil attack in storage, possibly more palatable to local tastes. Example: Kikuyu maize. Exotic varieties of maize can be collected to add genetic diversity when selectively breeding new domestic strains
• Hybrids. High yielding but also requiring large amounts of fertiliser. Seed from hybrids cannot be saved for planting so new hybrid seed is required each year.
• Composite (e.g. “Katumani”, “Coast Composite”). These are stabilised varieties and new seed is not required each year. If proper selection procedures are followed, farmers can use their seeds selected from their harvest.

Highland Maize Varieties

These varieties are bred and recommended for medium to high altitudes (1500-2400 m) where day temperatures seldom exceed 28degC during growing season and where the night temperatures drop to as low as 80degC. Rainfall requirement ranges from 800-1500 mm. Where similar conditions prevail in the highlands of Tanzania, Uganda and Ethiopia these varieties are recommended. Examples in this group include “H 6210”, “H 6212”, “H 6213”, “H 629” and “KH 600-15A”

Medium Altitude Agro-Ecozone

Altitude range is between 1000 and 1800 m. Some of the varieties in this category include “H513”, “H 515” and “H 516”. These varieties are commonly grown in coffee growing belts maturing in 4-5 months. The favourable rainfall is between 750-1000 mm

Transitional Zone

The altitude in this zone falls between 1000 and 1500 m where the temperature ranges from 12 to 30degC and has rainfall similar to that of high altitudes. “Hybrid 624” is a typical example in this category.

Lowland Agro-Ecozone

Pwani hybrids (“PH 1” and “PH 4”) and “Coast Composite” are fairly short varieties resistant to lodging and more tolerant to moisture stress and recommended for altitude range of 0-1250 m. above sea level with 400 mm of rainfall. They have an added advantage of good husk cover hence reduced crop loss though bird, weevil attack and ear rots. They are also suitable under inter-cropping systems.

Dryland Agro-Ecozone

Examples in this category include “Katumani Composite B” and “DLC 1”. Katumani “Composite B” is a fast growing open pollinated variety, which is fairly short and produces short cobs. It is a drought escaping variety flowering within 60-65 days and maturing within 90-120 days. The variety performs well within altitudinal range of 1000-500 m above sea level and is a variety for marginal rainfall areas. The variety requires 250-500 mm of rain, and has performed extremely well in arid marginal areas in many parts of Africa particularly in Somalia, Ethiopia, Sudan, Tanzania and Namibia “DLC 1” also open pollinated is recommended for arid and semi-arid regions. This variety flowers earlier than “Katumani Composite B” by about 4-7 days and is shorter but more prolific. Under unfavourable conditions the variety performs better that “Katumani Composite B”. The variety is best suited where rainfall duration is short and amounts to less than 350 mm. The variety is a good substitute where rainfall is erratic and can be recommended for arid marginal areas in the region as “Katumani Composite B”.

Propagation and planting

Maize is always planted through direct seeding. Maize should preferably be sown early in the season, as soon as soil conditions and temperature are favourable. Delayed planting always leads to reduced yields. In Kenya there is a drop of expected yields of 1-2% every day planting is delayed (AIC 2002). Hand planting requires 5-10 man-days/ha. Seed is dropped in the plough furrow or in holes made with a planting stick. Planting may be done on hills or in rows, on flat land or on ridges. On heavy soils ridging is advisable, to improve drainage. 

For pure stand of maize in Kenya the Ministry of Agriculture recommends spacing between rows of 75 cm and between seeds 30 cm for all areas with adequate rainfall, resulting in a total plant population of 44,000. In the coffee zones this can be increased to 75 cm x 25 cm giving total plant population of 53,000 plants/ha. In dry or marginal areas the recommendation is to increase spacing to 90 cm between rows and 30 cm between seeds – total population 37,000 plants /ha. Approximate seed rate is 25 kg/ha.The depth of planting is commonly 3-6 cm, depending on soil conditions and temperature. Deep sowing is recommended on light, dry soils. Animal manure or fertilisers are applied at the time of planting. 

Weed control 

Weed control is very important. Maize is very sensitive to weed competition during the first 4-6 weeks after emergence. It should be planted as soon as possible after the preparation of the seedbed. Inter-row cultivation to control weeds and to break up a crusted soil surface may be done until the plants reach a height of about 1 m. In Kenya 2 weedings are necessary for most maize varieties, though a third weeding may be necessary for varieties that need 6 to 8 months. Weeding by hand requires a minimum of 25 man-days/ha.  

Water management

 Irrigation is used in areas of low rainfall and is particularly valuable at the time of tasseling and fertilisation. Irrigation is necessary for production of green maize.  

Fertilisation

 Maize usually responds well to fertilisers, provided other growth factors are adequate. The quantity of manure applied by smallholders is usually very limited. Improved varieties can only reach their high yield potential when supplied with sufficient nutrients. A maize crop of 2 t/ha grains and five t/ha stover removes about 60 kg N, 10 kg P₂O₅ and 70 kg K₂O from the soil. Nitrogen uptake is slow during the first month after planting, but increases to a maximum during ear formation and tasselling. Maize has a high demand for nitrogen, which is often the limiting nutrient. High nitrogen levels should be applied in three doses, the first at planting, the second when the crop is about 50 cm tall, and the third at silking.

 Many soils provide substantial amounts of the phosphorus (P₂O₅) and potassium (K₂O) but this is not adequate enough, especially at the seedling stage. Apply P₂O₅ near the seed for early seedling vigour. K₂O is taken up in large quantities but plants’ requirement can usually be estimated by soil analysis. K₂O deficiency results in leaves with burnt edges and yellow or light green colour and empty cob ends, while P₂O₅ deficiency results in purple tinged leaves and hollow grains. Nitrogen deficiency shows as yellow or light green stunted plants.Phosphate is not taken up easily by maize and, moreover, some tropical soils are deficient in available phosphate. Zinc deficiency symptoms include shortening of internodes and light streaking of leaves followed by a broad stripe of bleached tissue on each side of the leaf midrib. Occasionally the leaf edges and interior of the stalk at the nodes appear purplish. It is advisable to apply organic manures to improve soil structure and supply nutrients, all before ploughing. 

Nitrogen (N) can be applied in organic farming via green manure (legumes fixing N directly from the atmosphere), farmyard manure (FYM) or compost. Phosphorus can be supplied through FYM, compost, and in the form of rock phosphate (available in East Africa as Mijingu rock phosphate). rock phosphate should be applied in the rows or planting holes at planting to promote root formation., Potassium can be supplied through FYM, compost and ashes. However, fertiliser recommendations based on soil analysis provide the very best chance of getting the right amount of fertiliser without over or under fertilising. Ask for assistance from a local agriculturist office. 

In rain-fed maize growing areas, plant seeds along with the first rain. This will allow roots to absorb the natural nitrates formed with bacterial action in the soil. Roots are susceptible to poor drainage, which causes stunted and yellowing of leaves. Stagnant water results to loss in N through leaching and denitrification (FADINAP, 2000). 

Intercropping

 In Africa maize does well when intercropped with beans or other legumes. The intercropped legumes should be sown at the time of first weeding in order not to crowd out the young maize plants. Since maize is a heavy feeder and takes considerable nutrients out of the soil, it can only be grown continuously on the richest soils or when heavily fertilised. Recommended legumes for intercropping in Kenya are beans, pigeon peas, cowpeas, groundnuts and soybeans. Other crops that have been tried with varying success include potatoes, cassava and pumpkin. 

Intercropping maize with beans and other legumes regulates pests (leafhopper, leaf beetles, stalk borer, and fall armyworm) and increases the land utility. Intercropping Canavalia (Canavalia spp.) with maize improves soil productivity. Sow Canavalia seeds 4 weeks after sowing maize. Place 1 seed/per hole in a row between maize rows with 50 cm between holes. Allow Canavalia to grow after harvesting maize until it is time to plant the next crop. Then plough the plant materials into the soil (CIAT, 2000). 

Intercropping maize with beans and squash enhances parasitism of caterpillars. This practice increases food sources for beneficial insects whereby increasing abundance of natural enemies. The intercropping system of maize-beans-squash is a low input and high yield strategy in the tropics. Maize yield is increased by as much as 50% over monoculture yield. Although the yields for beans and squash are reduced, the overall yield for the 3 combined crops is greater than when grown separately in monocultures (Agroecology Research Group, 1996).  

Push-pull Desmodium (Desmodium uncinatum) and molasses grass (Melinis minutifolia) when planted in between maize rows keep the stem borer moths away. These plants produce chemicals that repel stem borer moths. In addition desmodium supresses the parasitic witchweed Striga hermonthica. Napier grass (Pennisetum purpureum) and Sudan grass (Sorghum vulgare sudanese) are good trap crops for stem borers. Napier grass has its own defence mechanism against crop borers by producing a gum-like-substance inside its stem, this prevents larva from feeding and causing damage to the plant. Both grasses attract stemborer predators such as ants, earwigs, and spiders. Sudan grass also increases the efficiency of natural enemies, in particular parasitic wasps, when planted as border crops (Herren; Pickett, 2000; ICIPE, 2006).

Alternative uses of maize in mixed cropping 

• Shading of vegetable crops by planting single rows between vegetables in areas of high intensity of sunshine can increase yields of intercropped vegetables.
• Use as support for runner beans for export or local consumption.

Harvesting

Maize can be harvested by hand or by special maize combine harvesters. The stage of maturity can be recognised by yellowing of the leaves, yellow dry papery husks, and hard grains with a glossy surface. Maize is often left in the field until the moisture content of the grain has fallen to 15-20%, though this can lead to attack by grain borers in the covered cobs. In hand harvesting the cobs should be broken off with as little attached stalk as possible. They may be harvested with the husks still attached. These may be turned back and the cobs tied together and hung up to dry.  

Yield

The world average yield in 2014 was 5,616 kg per hectare. Average yield in the USA was 10,732 kg per hectare, while in Africa it was 2,105 kg per hectare. Average yields in Kenya in 2014 was 18 bags/ha (1,660 kg/ha) (FAOSTAT, 2014).  

Handling after harvest

The major problems in most maize-producing areas are reducing the moisture content of the grain to below 13%, protection from insects and rodents, and proper storage after harvest. High moisture content with high temperatures can cause considerable damage such as development of aflatoxin producing fungi making the product unsuitable for human consumption.Maize for home consumption is either sun-dried on the cob for several days by hanging up tied husks, or put in a well-ventilated store or crib. Easy test for moisture content: take a few grains and try to crush them with your teeth – below 13% moisture level the grains are extremely hard and almost impossible to crush this way. Shelling (the removal of grains from the cob) is usually carried out by hand, though several hand and pedal-powered mechanical shellers are now available. The average recovery is about 75%. The shelled grain is dried again for a few days and then stored in bags, tins or baskets. 

The optimum moisture content for storage is 12-13%. In Indonesia seed for the next crop is generally selected from the last harvest. The selected cobs are stored at home in the husk above the fireplace to prevent losses by insects. Crop residues are removed from the field and then used as fodder, fuel, etc.