Preparing for post-harvest : The best methods for and economic advantages of drying grain
When grain is first harvested from the field, as well as various items of dry matter that you'd expect to find, yields tend to contain unwelcome levels of water too.
Whilst water is necessary for plant growth and grain production, excess moisture after grain maturity can lead to a variety of storage related problems - viewers of Amazon series Clarkson's Farm will have seen what can happen when this is not done properly.
Grain moisture content and temperature play a key role in determining safe storage life and is typically expressed as a percent of the grain weight, so 100 pounds of 13 percent moisture content grain contains 13 pounds of water and 87 pounds of dry matter rice.
As a general rule, dryer grain and cooler temperatures increase the length of time that the grain can be stored safely for, with wetter grain and warmer temperatures vastly increasing the potential for pests, insects, mould and fungi - which will in turn have a negative influence on both the quality and market value of your grain.
Therefore, the primary objective of grain drying and storage should always be to manage the temperature and moisture of the air around the grain, with a view to minimising losses from the previously listed factors, whilst affording us the opportunity to hold grain for longer whilst we wait for the best-selling times to arrive.
Maintaining grain quality requires drying the grain to safe moisture content levels after harvest followed by lowering and maintaining the grain temperature within a few degrees of ambient air temperatures. Therefore, in addition to more control of harvest timing, there are potential economic advantages to on farm drying and storage.
Controlling the uncontrollable
The various grain drying strategies found throughout the world often depend on uncontrollable conditions including the volatility of the local climate and the availability of labour. These approaches include field drying, natural air drying, low temp drying, high temperature drying or dryeration, with allowing grain to dry in the field still the most widely used method.
In many cases, partial field drying is often used in conjunction with postharvest drying to reach target storage moisture content. The combination and dryeration techniques are done by partially drying grain with high temperature dryers, and then the remainder of the drying process is done with low temperature air and fans. Although these techniques are typically faster, they do consume huge amounts of energy compared to the more natural alternatives.
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Written by Andrew Wilkinson, Milling and Grain magazine, UK