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Crop Quality Measurement

Crop Quality Knowledge Bank

Grain Quality Risks

Low levels of temperature and moisture are essential to avoid risks to stored crop quality. Hot, wet grain will be at risk from mycotoxins, fungi and insect infestation.

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There is a safe storage zone (the hatched area on the graphic) which allows wet grain to be stored if it is cooled to 5°C or dry grain to be stored at temperatures up to 15°C.

The best option is to dry the grain to your target moisture and then cool it to as low a temperature as ambient conditions will allow.

Safe long-term storage requires regular crop monitoring and control of crop temperature. Ideally, crop temperatures should reach 5°C to reduce the viability of mycotoxins, fungi and insects.

Crop Monitoring

Crop monitoring gives early warning of quality problems and the opportunity to take action before the situation gets worse. It shows whether drying and cooling targets have been reached – which can save energy by avoiding unnecessary fan use.

Crop Temperature

Changes in temperature are the best indicator of grain quality, so temperature monitoring is essential.

  • Record crop temperatures weekly until the grain has cooled to 5°C (usually achievable by December); and then every two weeks thereafter.
  • Take one reading for every 100 tons stored 3 to 5 m deep. Use an imaginary 6m x 6m grid over the grain surface and take a reading in the centre of each grid square. This shows actual changes rather than location differences. In deeper grain, take readings using a 10m x 10m grid.
  • If Pile-Dry Pedestals and Fans are used to ventilate grain, measure the temperature at the mid-point between groups of 4 Pedestals since this is the last point to cool.
  • Take readings within the top 1.5-2 m of grain depth. This is where any change in temperature will be seen.

Ambient Temperature and Cooling Crops with Ambient Air

Measure the air temperature regularly:

  • inside the store if you are ventilating with Pile-Dry Pedestals
  • outside the store if you are blowing air in using underfloor ducts

Measure when fans are operating and at the beginning and end of each day when air temperatures can change quite rapidly.

If ambient air is cooler than the stored crop then ambient air ventilation will cool the crop. If fans are used when the air is warmer than the crop, the temperature will rise again. This wastes energy and means the crop will take longer to cool.

Ambient Humidity and Drying Crops with Ambient Air

To ensure drying targets are reached energy-efficiently, it is essential to know the humidity of the air that will be used for drying grain. Damp air will not normally affect grain moisture, but can reduce drying system efficiency if it enters the grain.

If ambient air is drier than the stored crop then ambient air ventilation systems can dry the crop. The ability of air to dry grain depends on the relative humidity (RH) of the air and its temperature. Warm air can hold more moisture, so is more effective at drying.

The relationship between grain moisture and air RH varies with air temperature. The point at which grain can be dried by air of a particular RH and temperature is the equilibrium relative humidity. These points can be joined on a graph to give a guide to see if air of a particular RH can be used to dry grain.

To decide if ventilating fans can dry the grain using ambient air, measure ambient RH and grain moisture and refer to the graph below:

In the example shown, air of 77% RH at 20°C will dry grain down to 17% moisture. To dry grain down to 15%, the air needs to be at 66% RH or it needs to be warmer.

This information is a guide only and is given more comprehensively in the HGCA/AHDB Grain Storage Guide. If you do not have a copy it can be downloaded using the following link:

The Importance of Accurate Grain Sampling

According to HGCA/AHDB, poor grain sampling and analysis costs the grain industry at least £2.5 million each year. Failure to market the right specification of grain results in loss of quality premiums, additional haulage and administration charges. These costs have risen sharply compared to the grain price and can make the difference between profit and loss.

To allow assessment of quality, value and storage potential, a series of samples should be taken using a modern, multi-aperture spear, at least 1.5m long, capable of being opened and closed by the operator. Such spears are emptied through a single orifice into a container. The results form the basis of any sales campaign, allowing grain to be segregated by quality and variety. Producers can then match grain batches to the buyer’s specific needs.

This information is a guide only and is given more comprehensively in the HGCA/AHDB Grain Sampling Guidelines. If you do not have a copy it can be downloaded using the following link:

The Importance of Measuring the Hectolitre Weight of Grain

When harvest quality is poor yields can be 5-10% below the long-term average and grain will have a low specific weight. Normal target weight per given volume would be 76 kilogrammes per hectolitre (Kg/hl), but readings as low as 50 Kg/hl can lead to significant deductions at the point of sale. Measuring specific weight on farm means knowing in advance what the likely outcome of a sale will be. Various things can then be done to raise the level of specific weight and it is much cheaper and simpler to do this before the grain is loaded and transported.

A confusion of terms!

The concept of hectolitre weight can be confusing because of the words used to describe it. Grain is now bought and sold according to its hectolitre weight, measured in kilogrammes per hectolitre (Kg/hl). It was previously measured and sold in bushels per acre and called bushel weight. The confusion arises because many people still use the phrase ‘bushel weight’ when they are actually referring to hectolitre weight.

The Importance of Wind Speed Measurement

Crop Spraying

Safe and effective crop spraying relies on measurements of relative humidity, wind speed and wind direction in order to minimise spray drift. Kestrel anemometers offer fast and certified-accurate measurements, making it easy to comply with regulations.

Crop Store Ventilation

Measuring the temperature, humidity and air speed within a crop store helps to ensure optimum airflow and ambient conditions. Using a Kestrel anemometer means that measures can be put in place to improve the air quality if required, such as installing a StoreVent Building Ventilation System.


Environmental data is essential in vineyard management. The Kestrel 3000 measures wind speed, air temperature, relative humidity and dew point to give early warning of frost protection requirements. If the air is dry (low dew point) heat loss will be greater, leading to the threat of a radiation freeze. Dew point and temperature also affect leaf wetness, which influences the development of downy mildew.

Livestock Environment Monitoring

Effective ventilation, temperature and humidity control of livestock facilities can reduce disease and prevent stock loss, as well as improve the rate of gain and feed-conversion efficiency. By using a Kestrel to monitor heat index, cooling measures such as increasing ventilation and misting the animals can be used at the right times. The wind chill feature warns of the critical time to provide additional feed energy and/or wind protection.

Crop Temperature Monitoring

Crop Sampling and Measurement

Crop Environment Monitoring