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