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Maize (Zea mays L.) is a major staple food in sub-Saharan Africa. It can be used as food and animal feeding, as well as a source of industrial raw material. In sub-Saharan Africa, maize is grown mostly by small-scale farmers under rainfed conditions mainly for human consumption. It is consumed as green maize fresh on the cob, or is baked, boiled or roasted.
Low yields in sub-Saharan Africa can be attributed to a variety of factors:
Soil moisture stress is a continuous problem for many farmers who continue cultivating maize under rainfed conditions. The erratic nature of rainfall, including distribution leads maize to severe soil moisture stress; reducing yields significantly.
The choice of appropriate maize varieties for a given location is important, as it makes a significant contribution to yield improvement. Furthermore, farmers must also consider the differences between modern varieties and traditional varieties. Wrong variety selection can lead to a poor harvest or total crop failure. Therefore, it is important to carefully select varieties that match with local growing conditions; including climatic conditions, nutrient level of the farm as well as cooking habits and dietary requirements of the consumers.
Small-holder farmers in sub-Saharan Africa grow traditional maize varieties. Seeds are collected from the farmer’s previous crop (recycling). These varieties have been developed based on specific farmers’ criteria and have become, over the years, adapted to local growing conditions (landraces). Besides being well-adapted to local conditions, such varieties are adapted to low nutrient levels and farmer cooking habits. Seed may also withstand local pest and disease pressures well. Traditional varieties are locally available and farmers can reproduce their own seeds for replanting. Nevertheless, yields of traditional varieties are generally low to moderate due to the poor methods of selecting seeds and to poor management.
Besides traditional varieties, there are several improved open-pollinated and hybrid varieties of maize in most local markets. They differ from one another with regard to characteristics such as yield potential, growth period and their adaptability to specific growing conditions like drought, pests or diseases. Hybrids are higher yielding than open-pollinated varieties, if grown under suitable conditions. However, hybrid varieties are expensive because new seeds need to be bought for every planting season. On the other hand, improved open-pollinated varieties are often higher-yielding than traditional varieties and farmers can produce their own seed of open-pollinated maize varieties, therefore reducing costs for purchasing improved commercial varieties.
Farmers can produce and multiply on-farm seeds from open-pollinated maize varieties. The following recommendations are meant to guide farmers in seed production:
Traditionally, farmers would restore soil fertility after a period of cultivation by leaving part of their land uncultivated for up to 5 years for fertility to restore, while new and more fertile land is cultivated for food production. However, the increasing population density has drastically reduced the amount of land available for farming, forcing farmers to shorten the fallow period or even to abandon the fallowing practice entirely. A natural short fallowing of overworked land will result in little or no improvement in soil fertility. It is therefore important to improve fallowing systems.
Experience has shown that the inclusion of improved short duration fallows of 1 to 3 years in rotations is important for significant improvement in soil fertility. Multi-purpose trees can be used to improve fallows. For example, improved fallows using Sesbania (Sesbania sesban) have been found to be a good way of adding significant amounts of nitrogen and organic matter to soil. Green manure cover crops can also be used. Soil fertility is improved and the productivity of following maize enhanced. It is recommended to establish improved fallows by planting different fallow species, as they make plant nutrients available for a longer period.
Successful weed management in maize is achieved by using a combination of measures including:
Two species of Striga are found in sub-Saharan Africa: Striga hermonhica in West and Central Africa, and Striga asiatica in Eastern and Southern Africa.
Striga is a parasitic weed that only grows by attaching itself to roots of a host plant like maize. Striga sucks nutrients from maize plants, leading them to be smaller and weaker. The attack brings to yield losses or even complete crop failure. Once Striga becomes well established on the ground it is difficult to control it, partly due to its high reproductive capacity. Striga also produces thousands of seeds, which can survive in the soil for several seasons and germinate only when a cereal crop is planted. Successful Striga management is achieved by using a combination of measures, also used for weed management, as follows:
Maize is harvested by hand on the cob in small-holder maize farming. Maize that is to be eaten green is ready for harvest when the grain hardens or when the silky flowering at the top of the cob turns black. At this full maturity stage the crop has a moisture content of about 30%. However, maize to be dried is left to partly dry in the field until all the leaves of the plants have turned brown. This bears the considerable risk of the grains spoiling by feeding birds. Many small-scale farmers wait too long to start harvesting because they lack suitable drying facilities.
Delayed harvesting can lead to rotting of the cobs, attacks by rodents, birds and weevils. It also allows fungal pathogens such as aflatoxins to spread, especially if the drying crop is rained on while still in the field. At harvest, the husks are removed from the cobs.
Quickly after harvest, the cobs should be dried under the sun before being shelled. If the grains are not well-dried, they will attract insect pests and mildew. To test whether the grains are dry enough, shake a handful of grains and half a handful of salt in a dry soda bottle for 2 or 3 minutes. If after the grains are allowed to settle, the salt sticks on the walls of the bottle, this means the grains still contain moisture. Grains should be dried again and tested repeatedly until no salt sticks to the bottle before being stored.
Drying should not be carried out on the bare ground, but on a cemented floor, on mats or tarpaulins on a raised structure like cribs or specially constructed drying sheds. This is to avoid the grains picking up moisture, dirt and insects. In case of open air drying, the grain should be protected from rain, night dew, domestic animals and birds.
The most common storage pests of maize are the Angoumois grain moth (Sitotroga cerealella), the larger grain borer (Prostephanus truncatus), grain weevils (Sitophilus spp.) and rodents (mostly mice). They can be managed by a combination of measures:
Bt-maize is genetically engineered to resist stem borer. It has been created by adding the genes from the soil bacterium Bacillus thuringiensis to the maize seeds. Bt-maize produces a toxin that kills the African white stem borer (Maliarpha separatella (Ragonot). Apart from being expensive, farmers are not allowed to save or exchange Bt-maize seed. Stem borers quickly develop resistance to Bt-maize and pollen could transmit the Bt-gene to local maize varieties.
After drying, maize should be stored in a clean and well-ventilated storage area, separating old from new grain stocks. There are different ways of storing maize.
Farmers who do not have adequate storage capacity are advised to sell off the grain immediately to avoid incurring losses. Well-dried and shelled grain is ready for milling into flour and further processing into other products.
The majority of maize produced in Africa is consumed locally. Maize has also become a cash crop with local industries such as for the livestock sector and breweries, due to economic growth, urbanization and rising incomes. There are growing domestic and continental market opportunities for maize throughout sub-Saharan Africa. Organic farmers can exploit this potential to position organic maize at the national and continental levels.
However, the market for certified organic maize is still very small, or does not exist. Many small-scale farmers are already using some organic practices such as intercropping. They can easily learn and make use of full organic practices to establish sustainable and productive production systems for their families and take advantage of the local market opportunities without organic certification.