Grain Storage Workshop

I recently attended an event run by Agricultural Supply Services at which Ken Wildey spoke about grain conditioning and storage.  Grain storage may not be as exciting to farmers as large shiny machinery that steers itself but keeping grain well and bug free may save you claims, redirection charges and additional cleaning bills of perhaps £20 per tonne and there aren't many tractors that can do that.

Ken is a knowledgeable and entertaining speaker who has worked in both research into grain pests and  commercial storage and grain store management and made the topic interesting and kept things fairly simple.  Below are a few rules of thumb:

Mycotoxins
Mycotoxins are produced by grains as a defence mechanism against infection by moulds.  The greater the incidence of the mould the greater the level of mycotoxin.  There are two major potential problems, the mould species which occur in the field and those which occur in the store.
Those which occur in the field are predominantly caused by Fusarium spp. and produce the Deoxynivalenol (DON) mycotoxin whilst those which occur in store are caused by Pennecillin type moulds and result in zearalenone (ZON) mycotixins.

They are mutually exclusive and so a high field risk mycotixin does not mean there is a high risk of a storage mycotoxin and a low DON risk does not mean that stored grain is at low risk too.  The risk factors associated with DON mycotoxins are reasonably well understood with the biggest hazard being maize in the rotation.  Ploughing helps reduce possible passage from season to season by burying trash and other than that rain at flowering can increase incidence but little can be done about that.  As a consequence DON tends to be regarded as having a seasonal effect and it is seen as being a "bad DON year" if poor climatic conditions occur.

For ZON the easy fix is to ensure grain is stored at below 18% moisture which will cease production of the mould.

Grain Temperature
Grain temperature is important because warm grain has the potential to generate moisture through condensation within the store.  Condensation can create small areas within the store that have a higher moisture content but can be difficult to detect and these can become a source of problems.  Grain should be cooled once in store with an target of a maximum temperature of 15 degrees centigrade within 2 weeks of harvest and a maximum temperature of 10 degrees centigrade four weeks later.

Provided air is cooler than the grain it will cool the grain and moist air is unlikely to make grain damp provided the air temperature is below the temperature of the grain as the air will warm as it passes through the grain and warm air can hold more water than cold air.  Therefore the air entering the grain is likely to be dryer than the air leaving the grain.  However, be aware that fans can raise the temperature of air by 2.5 degrees centigrade and reduces the relative humidity.

Storage Pests
Storage pests are sub tropical in origin and don't like cool temperatures which is another good reason to cool grain.
Sawtooth Grain Beetle will complete its lifecycle every 28 days but cannot do so at temperatures below 15 degrees centigrade.
Grain Weevil will take 4 - 5 months to complete its lifecycle at 15 degrees centigrade and will fail to do so at temperatures below 10 degrees centigrade.