Different ways and options for storing grain

July 2016

The consideration of the optimum methods and best options for storage of harvested grain crops begins in the planning stage prior to the planting of any grain crop.

Planning must be made for the storage of a variety of crops including cereals like maize, wheat, millet, sorghum, pulses like edible dry beans, cowpeas and oil seeds such as sunflowers, canola, and groundnuts as the main grains produced in South Africa. The various options chosen will be narrowed down to a single main crop or the various grains normally grown on you farm.

The scope of storage planning will also differ from a small scale farmer producing grain for own consumption and possible sale of the excess above family requirements to a commercial producer who will have to plan to store hundreds and in some cases thousands of tons of a particular grain.

The selling strategy of each farmer will be determined by the volume of grain to be harvested, the size of on-farm storage facilities and whether or not the crop will be delivered to commercial silos at harvest or retained in safe storage to be sold at the optimum price.

A medium to large commercial farmer without on-farm storage facilities would usually deliver to a commercial co-operative or company where the crop could be cleaned and dried to specifications and then sold immediately on the ‘spot’ market or hedged through the futures market mechanism for later sale at a better price.

Small scale farmers can also deliver a cleaned and quality crop to a commercial silo but can also consider various storage methods.

Harvesting

Harvesting whether or not by hand on a small scale or by medium to large combine harvesters must be done at an ideal stage after physiological maturity is reached and ideal moisture content. Commercial scale farmers with access to their own drying equipment can harvest before the recommended ideal storable moisture content is reached while the crop is on the lands. This reduces the possibility of crop damage from hail, too much rain, shatter losses, insects, mould, birds and rodents.

Please make sure you know what factors to look for in each crop mentioned above that determines the final physical maturity stage prior to harvesting.

Small scale farmers will harvest by hand and be able to sort, sieve, and clean their crops carefully before storing by hand while the modern mechanical combine will be able to produce a very clean sample that can be delivered to a commercial silo to be further cleaned, dried if required, classed and then stored.

Be familiar with the quality of seed required that will fall into a commercially accepted standard if you intention is to sell any of your crop that will surplus to your needs as a small family farming business.

Storage and storage facilities

The success of any method of storage whether on an open shed floor under roof, outside under a sail, in a container or sophisticated concrete or steel silo equipped with air circulation fans depends on the moisture content of the grain, prevailing ambient temperature and level of humidity in the surrounding air.

Remember that stored, the grains are alive and although they go through a period of dormancy will start to germinate when re-wetted by rain or by absorbing moisture from the air when the humidity is over 70%. It is quite a task for the smaller farmer in the high humidity in the coastal areas to maintain grain in storage without spoilage due to fungus, other pathogenic organisms and insects.

The biologically active grains respire during storage and produce heat and moisture. It is very important to be able to move and remix a crop by hand even when placed in bulk on a shed floor. Proper silos are designed with mechanised augers, continuous flow driers, elevators and fans to enable seed mixing and airflow management to bring the crop into the safe zones for long term storage.

Options for smaller farmers

Smaller farmers can store maize on the cob in various ways or dry the shelled maize in the sun before being put into bags. In the drier areas maize can be kept on the cob for longer before it is shelled and stored. Stored maize must be kept in any outside structure with a rainproof roof that enables side ventilation or in commercially available steel or plastic tank conversions that allow for efficient storage. However, always remember to monitor your crop for temperature and moisture content.

Monitoring temperature and moisture

Each grain crop has a characteristic equilibrium point of moisture content and temperature and humidity at which long-term safe storage will be achieved. These ideal moisture values at 27° and 70% relative humidity are shown in Table 1 for some of the grains mentioned above.

Monitoring

If you can afford a grain moisture metre, this is most helpful as you must monitor the moisture content of any stored grain on a daily or weekly basis to prevent any spoilage occurring. The commercial market only accepts grain meeting the national standards required. If you don’t have a metre, take a sample to your local silo operator who will give you an accurate reading and advise you accordingly.

Conclusion

Plan you storage options before you plant a crop and implement your plan so as to cater for the optimum conditions required for each different crop.

Article submitted by a retired farmer.

Publication: July 2016

Section: Pula/Imvula