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After harvesting

Safely storing yields

The statistical data reveal an extensive spread, but one aspect appears to be certain: depending on region and type of culture, significant crop yields are lost after harvesting, particularly in regions with supply problems. These losses determine whether firms operate profitably and in many cases even whether people go hungry.

"The losses amount to 15-25 percent on average, and anywhere from over 40 percent up to and including total loss in exceptional years", is how Martin Gummert describes the quantitative situation for rice cultivation. Due to the low harvest qualities, the post-harvest expert of the Manila/Philippines-based International Rice Research Institute (IRRI) estimates the related market loss to be 10 to 30 percent.

The market alone is not currently creating sufficient incentives for rice growers to produce more efficiently. According to Gummert, vertically integrated value-adding chains could help, but "risks such as monopolisation have to be avoided".

The "Sustainable Rice Platform" run jointly by the IRRI and the United Nations Environment Programme (UNEP) is fostering sustainable rice cultivation. The platform's successes include "hermetic storage". This relatively simple procedure with a system for storing quantities from 30 litres to 300 tonnes prevents the exchange of humidity and gas (oxygen) between the storage facility and the atmosphere. In tropical countries, the procedure has proved suitable for seed and harvests.

Prevention of pests
In Germany, post-harvest losses in the middle single-digit percent range are the benchmark. Scientists from the Johann Heinrich von Thünen Institute, the Max Rubner Institute and the Julius Kühn Institute break down the losses in a conservative scenario as follows: losses due to pre-cleaning 1.7 percent and storage 0.15 percent. The natural respiration of the harvested crops (metabolism) amounts to 0.85 percent, and 0.15 are lost during retrieval from storage. The scientific report to the Federal Government puts losses due to pests at 1.96 percent. In summary, the study arrives at a figure of around 5 percent post-harvest losses for Germany.

The temperature and humidity of the harvested crops and the same parameters in the entire storage facility form the central parameters for grain and oilseed. Poor conditions foster microbiological burdens due to moulds. DLG Information Leaflet (425) "Storing grain securely" states: "Measures to prevent pests such as the grain weevil take absolute priority over control". The DLG experts' basic rule is that the best pest is the one that does not get into the storage facility in the first place. "Whoever designs his operation hostile to pests will suffer fewer calamities later."

Regularly checking parameters
The DLG Information Leaflet qualifies this by stating that the introduction of insect pests can only be avoided completely in gas-tight silo cells or chambers without any residual grain. Insects did not develop in dry stored cereals with a temperature of less than 10°C; even mites only reproduced very slowly - assuming sufficient humidity. The main problem starts with the microclimate that fosters harmful organisms. This is controllable by controlling the three factors of dust, heat and humidity. Regularly checking the temperature remains vital. When the temperature rises, the alarm bells should sound: "Rising temperatures in the stored products indicate infestation with beetles, mites or moulds", warn the DLG Competence Center Agriculture's volunteer experts. 

Ears open for beetles
For a long time, the use of insecticides was the last resort to prevent major damage when pests managed to get into the storage facility. Many active substances, particularly those that farmers are allowed to use themselves, are no longer approved. Researchers at the Julius Kühn Institute are testing a method to differentiate and diagnose beetle infestations at an early stage. The "beetle sound tube system" detects the pests' feeding and crawling sounds. The tube can be used to introduce ichneumon flies into the grain silo. These lay their eggs in the larvae of the corn weevils and the growing ichneumon fly eats the early stages of the beetles. Once their work is done and no more food is available, the (dead) ichneumon flies can be simply removed by cleaning the grain.    

Such cutting-edge technologies are suitable for farmers in highly developed (agricultural) regions, since they can only be used with corresponding infrastructure. Elsewhere, simple methods help to safeguard yields after harvesting. More stable sacks through which pests are unable to penetrate are an 'instrument' that farmers in less developed regions (can) use to ensure that pests stay away from their harvested crops. Farmers are responsible for nutrition, whether using simple or complex methods. "Global Farming - Local Responsibility", the leitmotif of AGRITECHNICA 2019, puts this universal requirement in a nutshell.


  • Worldwide post-harvesting losses are considerable
  • Germany reveals losses of around 5 percent for grain
  • Prevention is better than cure
  • Controlling storage parameters
  • Simple and complex international protection methods

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