Maize

General Information and Agronomic Aspects

Highland Maize Varieties: These varieties are bred and recommended for medium to high altitudes (1500-2400 m) where day temperatures seldom exceed 28°C during growing season and where the night temperatures drop to as low as 80°C. 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 30°C 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

Some examples of maize varieties in Tanzania

• "Kilima, "UCA"(OPV): suitable for medium to slightly high altitude (900-1700 m); maturity of 110-130 days; yield potential of 45-65 bags of 90 kg / ha
• "Staha": suitable for low to medium altitude (1-900 m); maturity of 110-130 days; tolerant to drought and also humid conditions
• "TMV-1" (OPV) : suitable for low to medium altitude (1-900 m); maturity of 110-120 days"Katumani,
• "Kito": suitable for low to medium altitude (1-750 m); maturity of 90 days; yield potential of 22-30 bags of 90 kg / ha; drought tolerant
• "Situka"(OPV): suitable for medium altitude (500-1600 m); maturity of 110-120 days; yield potential of 45-65 bags of 90 kg / ha; tolerant to low nitrogen; resistant to cob rots, grey leaf spot and maize streak virus

Some examples of maize varieties in Uganda

• "Longe 4 (OPV)": suitable for low land to mid altitude areas; maturity of 100-115 days; yield potential of 40-55 bags of 90 kg / ha; tolerant to maize streak virus, rust and grey leaf spot.
• "Longe 5 (Nalongo) (QPM Maize)"; suitable for low land to mid altitude areas;  maturity of 115 days; potential yield of 40-50 bags of 90 kg / ha; quality protein maize with lysine and tryptophan amino acids; drought tolerant; resistant to maize streak virus, grey leaf spot; moderately resistant  to northern leaf blight.
• "Longe 8 H": suitable for mid-altitude; maturity of 120-125 days; potential yield of 88--10 bags of 90 kg / ha; excellent husk cover; tolerant to cob rots, drought and poor soil; resistant to maize streak virus, northern leaf blight and grey leaf spot; a very popular hybrid in Uganda.

Seed Selection, Planting and Field Operations

a). Seed Selection; 

Kenya seed company contracts specific farmers to grow maize for seed. The maize is then harvested and treated using Thiram-dindane to prevent pest attack and sold to farmers as seed. Farmers are advised to buy fresh seed for planting every season. This is because of the problem of reduced hybrid vigour in the first generation.

b). Land preparation; 

Land on which maize is to be grown should be prepared early to allow stubble enough time to rot. Ploughing is done using disc or mould board ploughs. Harrowing is done where the seedbed is rough, although a fine seedbed is not necessary for maize. Maize does well when grown in rotation with other crops such as beans, tobacco, cotton, groundnuts and Irish potatoes. Maize takes a lot of fertility out of the soil. Continuous cropping of maize should be avoided unless the soil is very fertile or where a lot of fertilizers are applied.

c). Planting Planting Time

Planting should be done quite early in the rains so that the crop can make maximum use of available moisture. Dry planting should be very crucial as delayed planting always reduces yields. Early planting also reduces attack by stalk borers.

Planting should be done within the first two weeks of the onset of rains. It is recommended that there should be at least 30 cm of wet soil throughout the soil profile before sowing. While the hole is still moist, place two to three seeds in an evenly-spaced line in each hole, with one pip at each side and one in the on the other side. Cover the seeds using the soil heaped next to the hole to leave a level surface. Make sure no stones or heavy soil clods cover the seeds. Leave the mulch cover between the holes intact. Try to complete planting in a day to ensure an even germination and later, an even crop canopy, which will shade out any weed growth.

Spacing and plant population per hectare The recommended spacing and planting density of maize for different areas is as shown in table .

The appropriate planting depth varies from 2 to 10 cm, depending on the weather conditions and the moisture status of the soil. In the highland and medium areas where the soils are well-drained sandy-loam soils, planting depth of 2 to 3 cm is optimal, as deep seed placement retards germination and emergence of maize seedlings. In dry and coastal low land areas where the soil is dry and/or sandy, maize seed should be planted more deeply (5 to 10 cm). This enables the development of a deep root system to obtain the needed water and nutrients. Deep roots penetrate far into the soil and use moisture and nutrients from the deeper depths of the soil.

d). Weed control 

Weeds in maize should be controlled right from the early stages of growth to reduce competition for moisture and nutrients. Two to three weedings should give the crop a chance to grow properly to the point where it can suppress the weeds. Hand weeding is mainly practiced.

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.  

e). 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.  

f). 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). For more information on organic plant nutrition click here.  

g). 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). For more information on push-pull click here  

h). 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 and Post Harvest Management

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.  

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).  

Post Harvest Handling

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.