Q. “I’ve been using dry inoculants for years since they’re easy-to-use. Recently, my forage came back from the lab with an abnormally high pH. When I asked about this, the lab mentioned that there is a difference in efficacy between dry and water-soluble inoculants and thought that may have something to do with it. Can you explain this?
A. The lab was right. There often is a difference in efficacy between dry and water-soluble inoculants, especially as dry matter at harvest increases. I always recommend water soluble inoculants over dry applied for this reason, provided the farm or operation is equipped to properly handle water soluble inoculants. As you noted, they do require a bit of additional work, but the benefit of the improved efficacy makes it worthwhile.
Inoculants contain live bacteria that remain dormant until rehydrated. Water soluble inoculants rehydrate, and therefore become active, quickly due to the water added at application. This allows the inoculants to work as soon as possible to achieve a faster pH drop.
On the other hand, dry inoculants rely on the crop’s moisture to rehydrate and, as a result, take longer to become active and lower the pH. This is especially true as the dry matter of the crop increases. As you likely know, the goal when ensiling is to drop the pH of the silage as quickly as possible for the best fermentation. Dry inoculants are not recommended for crops above 40% dry matter, as they will not drop the pH quickly enough for a good fermentation. In other cases, they can still work but are not as effective as liquid applied (water soluble) products.
The Silage Dr.