eBusiness Weekly
John Basera and Gorden Mabuyaye
Several studies have shown that stored grain losses can cost farmers 25-30 percent of their yield for the season in most cases due to high moisture, pest damage, fungal/bacterial infections, and rodent damage.
In other words, it means out of a harvest of 10 bags, 3 bags can be lost due to poor post-harvest handling (cleaning, storage, delivery and distribution). In Zimbabwe, the general farming populace, depend on stored grain for consumption, making it imperatively prudent to equip farmers with information on how best to handle grain, post-harvest, Nzaratakakohwa kwete! This article, targeting small-scale farmers, subsistence farmers and large-scale farmers (for on farm consumption/poultry feeds etc.), will highlight some important considerations and tenets for proper grain storage and handling, as farmers are harvesting their 2017/18 summer season grain crops.
Losses can generally be in two prongs i.e. in terms of quantities and consumer quality deterioration, and these ultimately lead to economic losses. The losses can occur at any stage between harvesting and consumption.
The major causes of post-harvest losses include among others; mechanical damage, excessive exposure to high storage temperatures, relative humidity/ moisture, contamination by fungi or bacteria, invasion by birds, rodents and pests.
Storage pests cause economic losses
The key to successful on farm storage is to anticipate and prevent potential problems through good in-store management practices, a process which comprises 3 basic steps i.e. sanitation (cleaning storage places, spraying and filling up cracks), chemical treatment with grain protectants (applying grain protectants to the grain at recommended moisture levels) and inspection (inspecting stored grain regularly and checking roofs of grain store and new pest infestations).
1. Sanitation in the grain store
Thoroughly clean out and fill in any cracks with mud or mortar. Burn the debris that is swept out of the grain store. Disinfect surfaces by spraying with Malathion or Kontakill, or paint with goat or cattle manure and ash (burnt sunflower stalks or aloe leaves).
Always use the oldest grain first. FIFO (First In First Out) maxim/principle is advised!
Never store grain that has already been attacked by insects, unless the insects have been destroyed or unless the farmer is using metal silos. Damaged grain will allow the entrance of diseases and the insects may have laid eggs in the grain, which may re-infect the stored grain.
Never let rodents make their home in the grain store – keep rodents out (Cats are an excellent way of controlling rodents).
Proper grain storage depends greatly on the storehouse. Build a good storehouse that keeps out thieves, rodents, moisture and other pests.
Only store dry grain and keep it dry. (Damp grain or damp air will cause grain to rot.) The ideal moisture content of grain for good storage is less than 13 percent.
Maize grain is prone to pest attack after reaching a moisture content level of below 13 percent moisture content, therefore it is advisable to harvest as soon as the crop reaches this moisture level to avert pre-harvest (in field) losses due to pest damage.
2. Use of chemical grain protectants Chemical treatment for long term storage
Maize in storage can be destroyed by many pests including: maize weevil (Sitophilus spp), Indian meal month (Sitotroga cereale), Flour beetle (Tribolium castaneum), Sawtoothed grain beetle (Oryzaephilus surinamensis), Lesser grain borer (Rhyzopertha dominica), Larger Grain Borer (Prostephanus truncatus), Rusty grain beetle and other storage pests. These post-harvest grain pests can cause significant yield losses (eat into your pocket) if left uncontrolled hence the use of stored grain chemical protectants is recommended. Several options are available.
Mix a grain protectant chemical thoroughly with grain during or before storage.
NB: there are other several registered chemical options on the market, we have mentioned 2 options for 2 important post-harvest grain pests.
NB: Always read chemical labels carefully, use safe practices and adequate protective gear during application. Always observe recommended pre-consumption intervals on the grain protectant labels.
Other practices which some farmers are using:
Eucalyptus (gum tree) leaves can be mixed with maize grain to reduce storage grain pests. The smell chokes away storage pests.
Alternatively, mix ash with the grain (3 to 10 kg ash per 100 kg grain). Burn a mixture of dry maize cobs, sunflower stalks and cow dung in order to produce the ash. Powdered (crushed) Syringa seeds also help to keep away insects.
3. Inspection
Farmers should always note that stored grain may deteriorate if: There are too high ambient temperature in grain storage places; The moisture of the grain is too high; The grain is diseased; Insects multiply in the stored grain; Rodents are allowed access to the grain; The grain is stored for a long time. It is important and advised that, stored grain should be inspected regularly for new infestations and problems.
Grain storage
Grain can be stored as “bulk” or bagged. The storage facility must be suited to the method of delivery. Bulk stored grain is loaded into bulk trailers/bins using augers. Bagged grain usually requires conveyors or labour for loading.
Bulk storage
There are many methods that can be used for bulk storage. Examples include: above ground silos, bulk containers and metal silos. Bulk storage is more economical in the long term than bag storage. Labour requirements and handling is minimised with bulk storage. It is more hygienic than bag storage. However, bulk storage has some disadvantages in that it is costly in terms of capital outlay for storage places and loading equipment as compared to bagging.
Conditions for bulk storage
The maize grain must be dry; with less than 13 percent moisture content. The storage facility must be structurally sound and designed for loading and offloading.
The storage facility must be weather tight and dry, thermally insulated from the sun’s radiation and also rodent free.
The facility must be convenient for inspection, fumigation and cleaning The facility must be provisioned to allow loading (of grain by augers) and offloading of grain (from the field)
Bagging
Bagged grain stores well in sheds or storehouses, provided that the roofs are sound and a damp proof barrier under the stacks is erected. Some farmers use dry gum poles or wooden raised platforms to keep stacks off the floor. Thoroughly check if the wooden platforms are not infested by grain storage pests before use. Grain should be treated with a grain protectant before bagging and storage and moisture should be below 13 percent. Stacks should be strongly constructed and sides must be inclined inwards to avoid tendency to collapse outwards. Rodents will have little or no access to internal bags if the bags are packed tightly. However use of rodenticides, cats and/ or traps in the store house to reduce rodent damage, is strongly encouraged.
Lanes of about 1m must be left around each stack to allow for inspection. Stacks must be clear of walls and roofs for aeration. Keep the place cool and dry.
Hermetic bags and metal silo grain storage technologies
The metal silo and hermetic technologies are the modern options of storing bulk grain suitable to most small scale farmers and even so for large scale farmers (for on farm consumption/poultry feeds etc.). These technologies can also be used for other crops such as beans, sorghum, millet, cowpeas and pigeon peas. These technologies are based on the maxim that no insect pest or fungal contaminations can survive in an air tightly sealed metal silo/hermetic bags. Metal silos come in different sizes and capacities from 0,5 tonne up to 3 tonne.
The science behind the functionality of metal silos is that, cleaned grain is stored in an air tight system where any living organism (pest/disease) present in the grain, will suffocate. At initial loading, a small candle is lit before the silo is tightly sealed. This is done to “suck” all the air from the silo, since combustion uses oxygen. The lit candle will extinguish as all the air is used by the combustion process, thereby suffocating any living organism (pest/disease) in the grain silo. It should be noted that, grain stored in metal silos does not need to be treated with grain protectants. The silo must be kept sealed for 30 days before opening for use through the outlet channel.
NB: Buy metal silos from suppliers accredited and trained by the Ministry of Lands, Agriculture and Rural Resettlement, only.
Parting shots
Larger Grain Borer (LGB) has become one of the most important and menacing pests in stored maize grain. The severity of an LGB infestation can be reduced by good store hygiene: cleaning the store between harvests, removing and burning infested residues, immersing grain sacks in boiling water and removing wood from stores or fumigating the store to eliminate residual infestations and treating grain with grain protectants for storage. Harvesting the crop as soon as possible after it has reached maturity will reduce the chances of attack by LGB and other storage pests. LGB populations build up, the longer the maize is kept in store, so it is important to inspect the stock regularly and treat grain when necessary.
Pesticides and fumigants are poisonous, so it is essential to follow all safety precautions on labels and consult agrochemical companies and extension staff before application.
Get a copy of Seed Co Farmers’ Guide for Grain Crops.
Seed Co Agronomy and Extension Services; Contact: +263 772 413 184 /+263 772 132 767; /[email protected]/[email protected]/www.seedcogroup.com/zw or twitter: @basera_john or @SeedCo2
