Maize Farming

1. Land Preparation

Ploughing and harrowing to be followed with the application of Non-selective herbicide-Glyphosate.

2. Planting Methods

Plant improved recommended varieties at a spacing of 30cm x 60cm. Planting is done between June - July in the savannah agroecological zone, but earlier between March - April in the humid south. Maize can be sown directly into the soil manually or with jab-planting without the associated cost of ploughing (zero tillage). Seed Rate is 20kg/ha.

3. Fertilizer Application

Fertilizer should be placed 5cm below and to the side of the seedling. NPK 27:13:13 formulation is currently recommended for maize; Apply recommended rates of fertilizer NPK 27:13:13 at planting if moisture is sufficient or 1 week after planting and top dress with Urea at 3-4 weeks after planting. 300kg of NPK 27:13:13 and 100kg of Urea is required per ha. Micronutrient formulations are also recommended for optimum yields as some important trace elements are not naturally available in most arable soils.

4. Weed Control

Weed at intervals until harvesting time is due. Use of selective herbicides like Nicosulfuron is recommended for weed control. Strategies of weed control include feeding to livestock, good agronomic practices, timely weeding.

5. Disease & Pest Control

Diseases can be difficult to identify in the field but should be diagnosed by a qualified plant pathologist.  It is advisable to plant disease resistant and stress tolerant varieties to prevalent diseases and pests in an area. – Late plantings also favour the diseases especially smut and rot diseases in the humid south, so plant on time.  Avoid planting maize after maize in the same field to check the build-up of diseases and pests.

 6.    Harvesting

Matured crops can be harvested as green maize. Dried crops can be harvested manually by hand or mechanically with the use of combined harvester. Traditionally, when maize cobs have dried enough for harvest, they are handpicked, hand shelled and dried in the sun.   This is very labour intensive, and has significant impact on the gross margin for maize. Another option is to harvest mechanically when moisture levels drop below 18% (in the north) and 22% in the south and then dried to below 13% for delivery or storage.

Harvesting methods:

    i.      Manual harvesting

In village farming systems the crop is often harvested by hand, and cobs are stored in traditional structures. Quite often, the crop is left standing in the field long after the cobs have matured, so that the cobs may lose moisture and store more safely after harvest.

During this period the crop can suffer infestation by moulds and insects and be attacked by birds and rodents.

Manual harvesting of maize does not require any specific tool; it simply involves removing the cob from the standing stalk. The work time averages 25 to 30 days per ha. Traditionally, maize cobs are commonly stored in their unhusked form. To improve their drying, it is often recommended to remove the husks from the cobs. Maize husking is usually a manual task carried out by groups of women. Some machine manufacturers have developed stationary maize huskers, such as the "Tonga" unit.

  ii.      Mechanized harvesting

A specific feature in maize harvesters is the header which leaves the stalks standing as it removes the ears.

The rates of work can vary from 2 hours per hectare with a 3-row self-propelled harvester to 5 hours per hectare with a tractor-drawn or -mounted single row unit. Generally speaking, harvest losses range from 3% to 5%, but they may be up to 10%-15% under adverse conditions. Depending on the situation, a single-row harvester can be employed effectively on up to 20 hectares or more; but the use of a multi-row machine demands several tens of hectares to be economically effective.

7. Threshing

Threshing or shelling is the process of separating the grain from the seed heads, panicles, or cobs. It is important to minimize the damage done to grain during this process as damaged grain is much more prone to attack by insects and fungi. Consequently, techniques that crush and damage grains such as beating with sticks or trampling by cattle, are not recommended. Also, the grain should be neither too moist (soft) or too dry (brittle) at the time of threshing; it is best done when grain is around 14 to 16% moisture content

Threshing methods:

          i.      Shelling and threshing

Traditional maize shelling is carried out as a manual operation: maize kernels are separated from the cob by pressing on the grains with the thumbs. According to the operator's ability the work rate is about 10kg per hour. Outputs up to 20kg per hour can be achieved with hand-held tools (wooden or slotted metal cylinders). To increase output, small disk shellers such as those marketed by many manufacturers can be recommended. These are hand-driven or powered machines which commonly require 2 operators to obtain 150kg to 300kg per hour. Another threshing method, sometimes applied in tropical countries, involves putting cobs in bags and beating them with sticks; outputs achieved prove attractive but bags deteriorate rapidly.

        ii.      Motorized threshing

Nowadays many small maize shellers, equipped with a rotating cylinder of the peg or bar type, are available on the market. Their output ranges between 500 and 2000kg per hour, and they may be driven from a tractor power take off or have their own engine; power requirements vary between 5 and 15hp according to the equipment involved.

8. Drying

After threshing, the maize kernels are dried in the sun either on mats, plastic tarpaulins or on a cement pad until the moisture content is below 13%, when the kernels are ready for sale or storage. During the drying process the kernels are raked across the pad to ensure even drying.  The moisture level in maize must remain below 13% if the maize is to be stored for a long period, to guard against mycotoxin contamination (aflatoxin), producing toxic side effects for consumers of the grain.

Drying Methods:

1. Sun Drying

The traditional practice of grain drying is to spread crop on the ground, thus exposing it to the effects of sun, wind and rain. The logic of this is inescapable; the sun supplies an appreciable and inexhaustible source of heat to evaporate moisture from the grain.

Sun drying of grain remains the most common drying method in tropical developing countries. It is first employed when the crop is standing in the field prior to harvest; maize cobs may be left on the standing plant for several weeks after attaining maturity. Although not requiring labour or other inputs field drying may render the grain subject to insect infestation and mould growth, prevent the land being prepared for the next crop and is vulnerable to theft and damage from animals. Drying in the field may also be carried out after harvest with the harvested plants laid in stacks with the grain, maize cobs or panicles raised above the ground and exposed directly to the sun.

Drying on flat exposed surfaces is the most common way of drying grain after harvesting and threshing. For drying small amounts on the farm grain may be spread on any convenient area of land. Contamination with dirt cannot be easily avoided with this method and cleaner dried grain can be obtained by drying the grain on plastic sheets, preferably black. 

2. Crib Drying

Compared with paddy, cob maize can remain at relatively high moisture contents, in excess of 20% with natural ventilation for considerably longer periods, from one to three months. The maize crib in its many forms acts as both a dryer and a storage structure. The rate and uniformity of drying are controlled by the relative humidity of the air and the ease with which air can pass through the bed of cobs. The degree of movement of air through the loaded crib is largely attributable to the width of the crib; research in West Africa has shown that crib widths should not exceed 0.6 m.

3. Solar Dryers

An improved technology in utilizing solar energy for drying grain is the use of solar dryers where the air is heated in a solar collector and then passed through beds of grain. There are two basic types of solar dryer appropriate for use with grain: natural convection dryers where the air flow is induced by thermal gradients; and forced convection dryers wherein air is forced through a solar collector and the grain bed by a fan.

8. Storage

Grains should be dried to moisture content between 12-13%) before storage. Maize grains are packaged in sacks and properly stored on racks/ pallets in well ventilated warehouses with room temperature (25 degree Celsius). Maize grains are susceptible to a lot of pest attack during storage. So the storage environment must be free from pests. The environment must not be humid (excess moisture in the atmosphere) to guard against fungal growth or disease infection.