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August 24, 2023

Tissue Testing for Sulfur: Collection Advice and Tips.

Part 2 of 2

Because you have a lot of skin in the game as a farmer, plant tissue analysis (tissue testing) provides an evidence-based approach to inform decisions around crop nutrients.

In Part 1, we shared insights specifically related to testing for sulfur – including crop-specific collection instructions. In Part 2, we share some general advice for collecting samples. The following guidelines apply to most crops.

Best timing for tissue testing

According to Dan Kaiser, nutrient management specialist at the University of Minnesota Extension, tissue testing should be done in the middle of the growing season.

“We want to avoid sampling too early in the growing season or too late in the growing season. This is because too early in the growing season, plants typically have not taken up a large portion of their nutrients, and too late in the growing season, plants tend to redistribute nutrients within their tissues and tissue concentrations will decline.”

Dan Kaiser

For most crops, there are three sampling stages:

  1. Early Vegetative Stage – This allows you to identify and address any nutrient deficiency in-season before it’s too late.
  2. Late Vegetative Stage – An ideal time to evaluate the effectiveness of a fertility plan.
  3. Reproductive Stage – Provides a good sense of season-long nutrient availability. Identifies areas of a field with deficiency challenges.

In some high-value crops, such as potatoes, weekly sampling may be recommended.

Collect samples throughout your field

Nutrient levels can fluctuate dramatically within a field. That’s why it’s recommended that samples be collected from various parts of your field to account for spatial variability. This may vary due to factors such as changes in soil texture and topography, as well as drainage patterns.

You should also include a mix between the superstar plants and the underachievers. Even a few with early signs of deficiency.

Alberta-based independent agronomist Ray Dowbenko suggests you include good notes with the samples. For example: describe the plant’s appearance and any symptoms (stunted, discolored, etc.). Dowbenko also says to note environmental conditions when the samples were collected, as this can affect nutrient uptake.

Which plants to avoid sampling

AgVise Laboratories shares the following collection tips with its clients:

  • Don’t collect plants that have shown signs of deficiency for more than ten days.
  • Don’t include plants that are stressed by disease.
  • Avoid collecting plants from excessively wet soil, herbicide drift, cultivator damage, and other signs of stress.

Tissue collection tips

Every tissue testing lab will provide specific instructions for collecting samples. These general tips apply to most situations:

  • Follow lab instructions on which part of the plant to collect… and at what growth stage.
  • Remove excessive dust or any soil from the plant by brushing or dusting the plant.
  • Never wash the sample. This could remove some of the nutrients.
  • Collect and return samples in the envelopes provided by the lab. These are usually paper.
  • Never put samples in plastic bags. The humidity can cause mold, which will render the sample useless.

Kaiser adds that you should also avoid collecting from the end of a row, where crops tend to be less healthy due to lower nutrient concentrations.

A tissue test won’t provide all the answers

Ray Dowbenko says tissue sampling or soil testing will help you better understand what is happening in your fields so that you can make smart, informed management decisions.

Yet, as he reminds us, a  tissue test alone will not provide sufficient insights to make an agronomic recommendation.

“Not all ‘apparent’ crop problems are related to soil fertility. Factors such as disease, herbicide injury, soil pH, drainage, seed quality and climate could be at play.”

Choose a reputable lab and crop advisor

There are many testing laboratories across North America. Your local crop advisor can help you choose the right one. They will help you interpret the results and make recommendations based on their local knowledge and understanding of your fields.

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