Maize harvesting is an essential part of the maize farming process and should be carried out timely. Delayed maize harvesting leads to loss of yield caused by pests and diseases as well as lodging and damage by birds. Maize harvesting varies with regards to climatic conditions in an area. In dry areas, the maize can be left to dry on the field for a prolonged period of time; on the other hand, in wet areas it should be done as soon as the crop matures, between 2 to 3 days without rainfall.
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Harvesting Time
The time for maize harvesting is determined by the purpose of the yield. Maize harvesting done for silage should be done earlier before the cobs are too dry. On the other hand, maize harvested for grain purposes should be reaped any time after one week of physiological maturity. If maize harvesting is delayed, insect infestation and fungal contamination occur. In addition, the grain dries beyond 15% moisture content required for safe storage. The physiological maturity of the crops be identified by either of these two techniques among others:
Colour of the Maize plant
A key indicator that maize harvesting is due includes crop colour. The husk cover of the crop happens to be one of the key identifiers. The husk cover starts to turn yellow or dry while the remainder of the plant is green. Note that the maize crop can also be fully mature even if the whole plant is typically still green. For this reason, a farmer should also inspect the kernel of the maize cob.
Kernel Maturity
The maturity of the kernel, as stated earlier, is also an important in determining when maize harvesting should be done. In order to find out if the kernel is mature or not, the farmer should collect about 5 maize cobs to be used as representatives of the yield maturity. Leaves are pulled back then using fingernails, press into the kennels. This should result in in a soft cheese texture at top of the cob and leave no indentation in kernels in the middle and bottom. Another way to determine the maturity of the kernels is by breaking the cobs in half. A noticeable stroke will point out where the solid yellow starch changes to the milky white sugar portion of the kernel. 1/3 to 1/2 of the kernel should be yellow starch.
Maize harvesting methods
Maize harvesting can be done manually or mechanically depending on the size of the farm. Commercial farms often employ mechanical methods whereas subsistence farmers tend to hand harvest their crops.
Hand harvesting
This is a manual maize harvesting method whereby the ears are removed from the standing plants by hand and are left to dry in the sun. Another common hand harvesting methods involves cutting the whole plant, placing it in stacks while still green. Once it is dry, the ears can be picked and threshed or the entire plant with the ear can be utilised as maize hay. Alternatively, the plants can be left in the field to dry and the ears harvested. Threshing and shelling of the maize is also done by hand. Maize kernels are separated from the cob by pressing on the grains with the thumbs. An alternative method involves putting cobs in bags and beating them with stick.
Mechanical Harvesting
Mechanized harvesting of maize is done with corn-pickers or combine-harvesters. Corn-pickers and combine harvesters are machines that simultaneously harvest, shuck, shell, and clean the maize crops. The machine should be operated by a skilled individual.
Harvesting
Maize harvesting should be delayed while plants have green leaves if there is a chance of rain. When maturity has been determined, the maize is harvested from the field. Cutting height and chopping length are an important part of this process. Cutting height depends on the different types of hybrid and growing conditions. The remaining stubble after harvesting serves as ground cover mulch to assist the establishment of the next crop thus should not be cleared.
Threshing/ Shelling
When the maize is dry enough, threshing is done manually or using machines. The precision of the threshing machine should be checked before use to reduce grain breakage. Manual threshing is commonly done by beating maize cobs with a picket. Grains should be threshed when the moisture content is about 22% to 26% to minimise breakage. After completion of the threshing process, the maize is dried for storage.
Drying
Drying is an important part of maize harvesting. Poorly dried maize festers during storage. Effective drying is done by appropriate machinery as it is easy to determine the moisture level of the grains. A considerable number of farmers dry their maize using solar based methods. This involves drying the maize in the sun. The down side of solar based drying methods is that it takes longer to reach the ideal moisture level and it is difficult to identify the appropriate drying temperature. It is therefore important for farmers to be cautious when drying maize in order to reach the appropriate moisture levels.
Storage
The recommended moisture content necessary for safe storage is approximately 10% to 13%. Fungal growth and mycotoxin production can occur within a few days if the grain is not properly dried and cooled before it is stored. Dry maize is less susceptible to fungal infestation during storage. Grain bins have to be cleaned prior to maize harvesting as does the dry maize. Maize should be stored in a well ventilated drying bin and inspected often to control pests. Some weather conditions are a threat to the grain’s storage life. Continued high temperatures shorten the shelf life of grains. Heavy rains increase mould problems thus grains deteriorate quickly. If infestation occurs, bad grains should be removed. After maize harvesting, good grains are to be placed in bags made of jute with good aeration. Bags made of polypropylene have poor aeration thus support fungal infestation. Registered insecticides can be applied to facilitate longer storage.
Maize Yield
Maize yield varies a lot depending on the efficiency of production, maize variety, and maize growing techniques. The yield of maize varies from 2 tonnes per hectare to 15 tonnes per hectare. Commercial maize production systems usually achieve a high maize yield per hectare due to the efficient maize production systems. Maize harvesting should done by skilled farmers. This is because a lot of yield is usually lost during the harvesting period. It is of paramount importance to make sure that the maize is harvested on time, dried properly, packed in an aerated bad and stored safely. An error during either of these stages can result in rot and infestation thus affecting the quantity and quality of the harvest.
