Sampling blackgrass from patches of around 20 sq m should give consistent resistance status results, Lynn Tatnell, a weed scientist from ADAS said.


Detailed research on patch sampling were made in a recent DEFRA-funded LINK project on herbicide resistance, she explained.

“The results suggested that if you sample within 20sqm the results should be representative of that patch. But the results start to get more variable if you’re sampling from patches 20m to 50m apart.”

But how much growers sampled ultimately came down to cost, she recognised. That meant if growers were only doing one sample from a field then it was better to sample from individual patches across the field and then take a representative sub-sample than just sampling from one patch in the field.

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