Grain Moisture Meter

Grain Drying

Drying is an essential step in storage of grains. When grains are harvested, they are generally have a moisture content of around 18-25% moisture content ([FAO], 2011). Ideally this value leans towards the lower end of this range. However, this is not the content that grains are ideally stored at, and the goal of the producer is to have the grains reach their equilibrium moisture content or EMC. The EMC is the point where a hygroscopic material, such as a grain, has reached an equilibrium between the moisture content of the grain and the humidity of the air ([FAO], 2011). This value fluctuates depending on the humidity of the air, and the temperature, and it is appropriate to store grains within 1-2% of the ideal moisture content ([FAO], 2011). The ideal storage values for wheat, maize and rice are all around 13% ([FAO], 2011; Ganesh, 1992; “On-Farm Stored Grain Management: Insect Management for Farm-Stored Grain,” 2009).  

Grain Moisture Content and Problems Relating to High Contents

The moisture content of grains and cereals is extremely important for grain producers. This is because a high grain moisture content, or a grain that is harvested prematurely creates conditions that are more favorable to spoilage ([FAO], 2011; Mills, 1989). This is the result of the increased biological activity, specifically anaerobic respiration, in grains with high moisture levels and of those harvested prematurely (FAO, 2011; Mills, 1989). The products of this respiration are carbon dioxide, water, and energy- liberated as heat, and these products create an environment where molds, bacteria and insects can thrive (FAO, 2011; Mills, 1989). When these pests are present in grain, they render them unfit for consumption or usage as seed (FAO, 2011).  Another problem associated with increased moisture content is premature germination of seeds ([FAO], 2011). It is important to note that spoilage is not only result of the moisture contents of grains, but it is a substantial contributing factor.

In Canada, there are many strategies producers use in an effort to prevent spoilage of grains. Table 1 shows these strategies as outlined by the Canadian Grain Commission. The strategies identified in this table revolve largely around maintaining a low moisture and heat level, as well as aerating stores to avoid localized areas of high levels (Mills, 1989). Although these strategies are centered around industrialized Canadian agriculture, the general themes and ideas are applicable to agriculture world wide. Grain drying before storage, followed by storage in waterproof, tightly sealed containers have tremendous impacts of preventing spoilage ([FAO], 2011; Mills, 1989).