Watering in Milorganite and Soybean Meal

I noticed a search term rising in my stats report and it's a good question.  How much water does Milorganite need?

Technically, none.  You don't need to water in an organic fertilizer to get it to work.  Natural rainfall will do that for you very nicely, and neither Milorganite nor soybean meal (nor any other organic fertilizer) will burn if you don't water it in.  That assumes you've applied a reasonable amount as large amounts of Milorganite can burn, but bag rate to double bag rate certainly won't be a problem.

Milorganite contains some water-soluble nitrogen, so until it's watered in nothing is happening at all.  Around a quarter inch of rainfall or irrigation is sufficient to move that water-soluble N into the soil to start work.

Soybean meal contains no water soluble nitrogen, so there's no immediate nitrogen release at all when watered in no matter how much water you use.  Other organic fertilizers will vary, but the percentage of water soluble nitrogen will tell you how much effect to expect immediately after watering.

The remaining sixty percent (or 100 percent for soybean meal) of water insoluble nitrogen has to decay and break down in the soil to become available to your plants.  That's dependent on moisture as well, so a constantly slightly to moderately damp environment will feature the fastest nitrogen release.

Too much water tends to expel oxygen from the soil, which is necessary for decay.  Soy and Milorganite will still decay under anaerobic conditions, but the results aren't quite as good.  Too little water will shut down decay and stop nitrogen release until rainfall resumes.

This is actually a good thing.  Soils that are too wet or too dry don't foster large amounts of plant growth to begin with, so reduced nitrogen release is appropriate for what the plants need at that time.