Premier Press

Summer 2000 vol. 7/no. 2

We’ve all had to deal with leftovers in the refrigerator. The flavor has changed and maybe the food is dried out. What do you do with it? You inspect it for mold, add a little moisture, a little extra seasoning and heat it up. Soilless mixes can also become stale after months of storage – any mix. Nutrients are consumed by microorganisms, the pH goes up as a result of lime and moisture, and the wetting agent breaks down. If the medium has gotten wet, the changes could be severe.

What should be done with leftover Peat-Lite Mix? The first thing you might want to do is to check the pH and EC at your greenhouse or send a sample to Premier Horticulture labs for complete analysis. If the pH is 6.0 or less and the EC is over 1.0, just use it as always. However, if the values are outside of the normal range for unused media, water in your plants the first time with 200 ppm of an acidifying fertilizer like 20-10-20 peat-lite. This will replenish the starter charge and possibly help to reduce the pH.

When the pH of the unused medium is too high for the intended crop, you might consider short term acid injection to neutralize enough alkalinity to lower your solution pH to 5.0-5.5. Thorough irrigation to the point of run-through using sulfuric or citric acid should reduce the medium pH below 6.0. Fertilizer should be included in the acid solution also. If you have pH and EC meters, as every grower should, check the results of these corrective measures. After a few initial fertigations with acid you should be able to return to your normal feeding regimen.

In cases where the wetting agent does not seem to be working well, add a remedial rate of wetting agent, such as PsiMatric from Aquatrols. You might need to apply wetting agent a few times to restore full wetting function to the mix. As a matter of fact regular injection of wetting agent at a low rate is a good idea for most growers. It can improve water and fertilizer distribution in any medium and enhance re-wetting for the consumer.

To prevent your peat-lite mix from getting stale:

Buy only what you expect to use within six months
Check the production codes and use the oldest mix first
Store soilless mix so that it is protected from sun, heat, water and contamination

If you have questions about the freshness of your mix, call Premier Horticulture Grower Services at:

1 800 424-2554 (US)
1 800 667-5366 (Canada)

Or, e-mail at:

grower_services@premierhort.com