Control shrinkage to prevent the invisible loss.
- isabelle7349
- Aug 22
- 6 min read
Updated: Aug 24
Grain shrinkage and expansion - Why talk about it?
In agriculture, the harvest represents the culmination of a year of hard work. Every hectare sown, every hour spent in the field, and every dollar invested translates into grain yield. However, grain is not an inert raw material: it is a living product that breathes and is hygroscopic, absorbing and releasing moisture.
This characteristic leads to a phenomenon that every producer is familiar with: grain shrinkage and expansion. These terms refer to the direct relationship between volume, weight, and moisture content. Understanding this dynamic is essential, as it directly impacts the farm's final income.
In this article, we will:
explain the relationship between grain volume, weight, and moisture content;
demonstrate the economic impact of delivering corn that is too moist (e.g., 17%);
analyze the financial losses associated with delivering corn that is too dry (e.g., 13.5%);
propose alternatives to reduce the risk of overdrying and maximize profitability.
Understanding the relationship between volume, weight, and moisture content
Grain composition
Grain is composed of two elements:
Dry matter (DM): this includes starch, proteins, lipids, and fiber.
Water (H₂O): it is the variable water fraction that determines the moisture content.
The equation is as follows:
Total weight = Dry matter weight + Water weight
Online calculator: Calculate weight loss due to drying
Example: 100 kg of corn grain with 15% moisture content contains:
85 kg of dry matter;
15 kg of water.
The effect of moisture content on weight
The market does not pay for water content, only for dry matter. Therefore, two batches containing the same amount of dry matter but with different moisture contents will have different weights. This means they will have different commercial values.
Batch A: 100 kg at 15% → 85 kg of dry matter.
Batch B: 100 kg at 17% → 83 kg of dry matter.
Visually, the gross weight appears to be the same, but the actual dry matter value is lower in batch B. The buyer therefore adjusts the price using a shrinkage factor.
The effect of moisture content on volume
Volume is often expressed in hectoliters (Quebec) or bushels (United States). One hectoliter of dry corn at 14.5% moisture content weighs approximately 72 kg. The more moisture the grain contains, the lower the weight per hectoliter, because water is lighter than corn starch.
Product | Actual density (g/cm³) | Apparent density (kg/hL) | Vacuum space ε (%) |
Water | 100 | 0,0 | |
Corn | 1302 | 72 | 44.7 |
Soybeans | 1232 | 75 | 39.1 |
Wheat | 1404 | 75 | 46.6 |
Barley | 1304 | 60 | 54.0 |
Canola | 1087 | 65 | 40.2 |
True and bulk density of the main grains marketed in Quebec. (1)
Thus:
Corn at 13.5% → approximately 73.5 kg/hL
Corn at 14.5% → 72 kg/hL (reference)
Corn at 17% → approximately 70 kg/hL
Quite rightly, when corn is dried, it gains weight. This means that #3 grade corn may be reclassified as #2 grade due to the increase in density during the drying process.
But be careful! A grain that has reached full maturity will gain weight. Conversely, a grain that has not reached full maturity may lose weight, especially if it is heated to a high temperature.
This chart (2) allows you to predict the specific weight of well-ripened corn before drying:
Moisture range | Amount to be added(kg/hl) | Amount to be added(g/0,5L) |
15.8 à 16.4 | 0.5 | 2.6 |
16.5 à 16.9 | 1 | 5.2 |
17.0 à 17.3 | 2 | 10.5 |
17.4 à 17.6 | 2.1 | 11 |
17.7 à 17.9 | 2.2 | 11.5 |
18.0 à 18.3 | 2.3 | 12 |
18.4 à 18.6 | 2.4 | 12.5 |
18.7 à 18.9 | 2.5 | 13 |
The cost of delivering low moisture grain
Why is it a problem?
At first glance, one might think that drier grain is always better. In reality, the producer loses marketable weight. Each point of moisture reduction reduces the total mass without increasing the dry matter
Concrete example: corn at 13.5%
Let's assume that a producer delivers 100 tons of corn at 13.5%.
86.5 tons of dry matter;
13.5 tons of water.
Compared to 100 tons of corn at 14.5%
85.5 tons of dry matter;
14.5 tons of water.
Excess dry matter delivered:
(86.5 Tm / 85.5 Tm) = 101.17%
Dry matter equivalent on a 14.5% basis:
100 tons * 101.17% = 101.17 tons
Loss of income:
101.17 tons - 100 tons = 1.17 tons
The dry matter is identical, but the producer loses approximately of 1.17 % marketable weight.
Consequences:
For every 100 tons -> 1.17 tons of corn at $250/ton -> Loss of $292.50
For 1,000 tons, $2,925
For 10,000 tons, $29,250
Other cumulative losses
In addition to weight loss, the following must also be taken into account:
Excessive fuel consumption for drying ($$)
Longer drying times and slower harvesting
Increased percentage of broken grain due to increased grain fragility
Increased risk of grain downgrading ($$)
The economic impact of delivering grain that is too moist
The penalty mechanism
When grain is delivered above the regulatory moisture content, generally 14.5%, the buyer applies:
A reduction based on the excess moisture.
Drying costs to bring the moisture content back to commercial levels
An additional penalty (shrinkage) to cover handling costs
The decrease is calculated as follows:
Decrease (%) = (delivered moisture − target moisture) / (100 − target moisture) × 100
Concrete example: corn at 17%
Let's assume that a producer delivers 100 tons of corn at 17% moisture.
Reference base: 14.5%.
Difference: 2.5 points.
Decrease (%) = (17% − 14.5%) / (100% − 14.5%) × 100 = 2.9%
Consequences:
Weight paid = 100 t – 2.9% x 100 t = 97.1 t.
At $250/t:
Gross value = $25,000.
Value paid = $24,275.
Decrease = $725 on the delivery.
In addition, there are drying costs charged directly (e.g., $1.25/point → $1.25/pt x 17 pts x 100 t = $2,125).
Additional risk
Beyond the financial loss, delivering grain that is too moist carries the risk of additional transportation costs. Some buyers may refuse the shipment if it exceeds a commercial threshold (often 15%).
5 alternatives to avoid delivering grain that is too dry
Accurate moisture monitoring
One key factor is to use a reliable moisture meter that has been calibrated using a rigorous testing protocol.
Modern devices, such as Perten's AM5200-A, allow you to test your samples quickly and accurately. By increasing the number of tests and rigorously monitoring your drying process, you will increase control over your grain moisture and crop weight.
Dryer automation
Modern drying control systems, such as agrilog's Drylog controller, optimize your dryer for uniform, high-quality drying and an ideal target moisture content of 14.5%.
Strategic aeration of your grain
Automated aeration allows you to even out the moisture content of the grain to the desired moisture level. It also prevents your grain from drying out at the bottom of your bins.
If you harvest grain that is too dry, an intelligent system, such as agrilog's Silog, can humidify it using the grain equilibrium principle. This means you use ambient air during humid periods to add weight to your harvest.
Grain blending
Grain blending involves combining batches of different moisture levels to achieve a desired average. Buyers can benefit from blending batches to optimize the weight sold while reducing their drying costs.
To facilitate monitoring of this type of activity, agrilog offers grain moisture sensors connected to the agrilog platform.
Example:
50 tons at 13% + 50 tons at 16% → 100 tons at 14.5%.
Savings on drying wheat at 16% of $18/ton: 50 tons x $18/ton = $900
⚠️ However, this process requires rigorous control and carries storage risks if the difference is too high. It is not recommended to mix grain that is more than 2% above the regulatory storage threshold. Aeration will also be necessary to promote moisture transfer between wet and dry grains.
Flexible sales contracts
Some producers negotiate clauses with buyers allowing for moisture tolerance (±0.5%) in order to avoid losses due to marginal over drying. For example, over several deliveries, a buyer will calculate an average moisture content and accept a slight excess of 0.5% moisture on a few trips.
Conclusion: Aim for precision!
Grain shrinkage and expansion are realities that every producer must deal with. Every point of moisture above or below the target can represent thousands of dollars in losses for the entire company.
Corn delivered with too much moisture results in direct penalties and drying costs.
Corn delivered too dry results in an invisible but very real loss of marketable weight.
The key is therefore to aim for the regulatory target with precision. This requires:
reliable measuring tools;
well-calibrated and automated dryers;
an appropriate aeration strategy;
rigorous work protocols (testing, calibration, drying, ventilation, etc.).
By optimizing the moisture management of your grain, you not only maximize your income, but also ensure the quality of your harvest.
(1) The density of products varies considerably depending on the volume occupied by the grain, its size, quality, reference moisture content, etc. The values shown are averages.
(2) Corn: Estimating test weight of well-matured corn after drying
References:
Corn: Estimating test weight of well-matured corn after drying
