Part 1-EC
Before you start sticking your seeds in for the upcoming growing season, consider this – what exactly is IN the potting mix?! While many of us are devoted to our favourite potting mixes, changes in formulation, or lack of supply, may result in a very different product than we are used to coming out of a similar looking bag. Instead of crossing our fingers and waiting to see how the quality (and quantity) of the sowed seeds turns out, some easy testing can be conducted in order to mitigate some potential issues before they wreak having on your upcoming cash crop.
Some of the most basic testing that can be done on a potting mix will reveal information surrounding electrical conductivity (EC), pH, and nutrient content. While nutrient deficiencies have a significant impact on seedling growth and development, today’s focus is going to be on the EC of your potting mix.
What is EC, and why is it so important to test in potting mix?
EC (reported as mS/cm, dS/m or mmhos/cm) measures how much electricity is conducted through a solution. In this case the solution we are referring to is a moist potting mix, and the reading indicates the concentration of ions or salts in the potting mix solution. EC will have a direct implication on a plants ability to take up water, and overall health.
Before we dig any deeper here, its worth clarifying that salts are not just sodium (Na+) and chloride (Cl-) ions, but are also essential plant nutrients:
- Calcium (Ca2+ )
- Magnesium (Mg2+)
- Potassium (K+)
- Ammonium (NH4+)
- Phosphate (HPO42-)
- Sulfate (SO42-)
- Nitrate (NO3-)
A potting mix with a high EC value has a direct effect on plant growth, especially when we are looking at germinating plants. For plants that CAN still germinate in high salt environments, and don't necessarily suffer a reduction in the number of successfully germinated seeds, there will likely be a visible impact on root and shoot development (left) compared to that of a healthy transplant (right). A delayed planting date, or weak seedlings at the time of transplant, could see a less successful transplant, later harvested product, and more susceptible crop to pest and disease pressure.
Assessing substrate EC can be done in a few ways. Ideally samples are submitted for testing, which will reveal a nutritional breakdown as well as pH and other key features of a growing mix, depending on the test selected. At-home tests are less accurate, as a high degree of variability is introduced once on-farm equipment is involved, as well as differences in the ratio of potting mix to water, the quality of the source water used to create the potting mix slurry, and the accuracy of equipment storage and calibration.
Lab services offering potting mix analysis:
NSDA Analytical lab: request test G1P
A&L Labs: request test S8-S9B under ‘greenhouse mixes’
If you have any questions surrounding your potting mix, please don’t hesitate to reach out to our Protected Crop Specialist, Talia Plaskett, and stay tuned for more posts like this!
Posted by: Talia Plaskett
