OMAFRA: Time To Take Soil Samples

This week’s provincial field crop report suggests fall is an ideal time to take soil samples to prepare for the next growing season.

OMAFRA specialists point out there have been some significant changes in soil sampling technology in recent years.

That includes the use of sensors mounted on a ground-based vehicle, like an ATV – or an aerial vehicle, such as a drone – usually equipped with GPS.

Those sensors can help detect crop characteristics like mass, health and moisture.

They can also measure soil properties such as organic matter, salt, clay and water content.

However, the Ministry says those sensors may not be able to explain why variations exist in the field, or how to manage it.

The sensor output calibrations are not well established for Ontario conditions, so farmers are advised to check that the output they’re getting matches reality in the field by either soil or plant sampling.

Whatever method is used, the ministry says the results can generate nutrient level maps and define management zones for variable nutrient and lime applications for the next growing season.

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Ontario Field Crop Report

Crop Fertility & Nutrient Management

Soil Sampling Guide: Bonnie Ball, Nicole Rabe, Doug Aspinall
Fall is an ideal time to take soil samples in preparation for developing a fertility program for the next growing season. Recently there have been some significant changes in technology to increase the accuracy of soil sampling. A soil sample is a composite of cores collected from an area no larger than 10 ha. There are a number of methods to divide fields into sampling zones: past field boundaries; management differences; variation in topography, soil type, and/or the crop. This is referred to as Directed Sampling. Examples are given below. Ideally sample zones are based on more than one parameter. Sensors, mounted on ground-based (ATV etc.) or aerial vehicles e.g. satellite, aircraft, Unmanned Aerial Vehicle (UAV), usually equipped with GPS, can help delineate sample zones. These include: optical sensors, which measure how light is reflected or absorbed and get used to indicate crop characteristics such as mass, health, moisture, and nutrient status via vegetation indices e.g. Normalized Difference Vegetative Index (NDVI), and soil properties such as organic matter (OM), CEC and moisture; and soil electrical conductivity sensors, which get used to indicate soil CEC, salt, clay, OM and water content. Other sensors exist and more will come to market in future. While sensors can show where variation exists in the field, they may not tell what causes it, or how to manage it. In some cases, calibration of sensor output is not well established for Ontario conditions, so it is important to check if sensor output matches reality in the field by soil or plant sampling. Soil test results from directed sampling can be used to generate nutrient level maps and to define management zones for variable nutrient and lime applications.