When can I take a soil sample?

Spring is finally here, I think. It’s been a bit of a tease this year. And with some warmer days and calendars creeping closer to acceptable planting dates, I’ve had a lot of questions about when a soil sample can be taken. Last week was too early, this week we’re getting closer, I don’t think next week will be quite time yet though. There isn’t a calendar date for this, but waiting an extra week could have significant differences in your results. 

Spring in the soil

As the ground thaws and warms, anaerobic microorganisms will come out of dormancy and wake up first. Those are the ones we can smell – that smell of spring in the air. Those aren’t the ones we want to measure though as they are the detrimental microorganisms. As the ground continues to warm up and dry out after being frozen and snow-covered all winter, the aerobic microorganisms will come out of dormancy. However, it won’t happen overnight. It might take a few weeks, or longer, depending on the weather. If the conditions become less than optimal they may go dormant and re-awaken when the temperature allows.

In Ottawa we’ve had one day of spring coats followed by another day back in winter wear, and the last of the snow just melted during heavy rain a few days ago. However, with warmer days and some sun forecasted, I expect the soil to wake-up soon. 

Ideal Conditions

Once your soil is no longer cold, or soggy wet, wait one more week before taking a sample. That extra week will allow for more wake-up and maybe a bit of growth among the aerobic microorganisms. Remember that ground that has mulch or a cover crop growing will warm up faster than bare ground. 

Planting and Planning

Don’t worry about getting a soil assessment done before planting. If the aerobic microorganisms aren’t fully awake, an assessment won’t be accurate as the biology will change. Soil biology can be altered after seeds are in the ground.

When assessing compost, look for the same signs of warmth and moisture as the soil, but compost will likely warm up faster and can probably be assessed earlier. 

If you’re regenerating a large space and have an early start date, feel free to reach out so we can determine the needs of the space and how early the soil can be sampled. Otherwise, wait until a bit longer so your assessment considers an optimal amount of soil biology. Assessment reports are provided within 48 hours of receiving the sample and this timeline can be incorporated that into your project planning.

Published by juliamdupuis

Green Angel Sustainability Consultant. Environmental Chemist. RRU MEM Graduate.