Consider this when fertilizing before a rain

Categories: Lawn Care Pesticide and fertilizer application Water

A look at this week’s weather forecast prompted this post:

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This time of year I get a number of inquiries on fertilizer application.  One of the keys to proper application is the need to water it in.  For people who depend on rainfall for this, it’s only natural (and smart) to check the weather carefully before making the application.  It is important to note that rain can be a two-edged sword.  A heavy thunderstorm can wash the fertilizer off-site, doing virtually nothing to benefit your plant material, and potentially causing additional problems with our streams, ponds, and lakes.  Excess fertilizer runoff is a significant problem in both rural and urban areas.

I try my best not to give advice with “it depends”, but unfortunately, this is one of those cases where that is the best I can do.  Here are a few thoughts to keep in mind to help you with the decision-making process:

• How dry is the soil?  For example: we are in good shape at the surface right now, this will help as the surface moisture will help to soften the fertilizer and help “stick” it to the soil so it less likely to runoff.  A dry-hard surface behaves much like a freshly waxed car, the water tends to run off instead of soak in.
• Is their moisture in the air?  Depending on the products chosen, even high humidity can help the fertilizer to begin to break down.  Good morning dews will accomplish the same thing.
• Is their likely to be light to moderate rains or will it be “squall line” type thunderstorms where the rain comes hard and fast?
• Is it even time to apply?   Fertilizing warm season turfgrass too early in the year for the turf to take advantage of the nitrogen is a common problem.   This week is plenty early enough to be applying nitrogen fertilizer to your lawn for the first time this season.
• How close is the application to a body of water (or a hard surface that drains directly into a body of water)?   OSU has done some very nice research on reducing the fertilizer (and pesticide) runoff.  It is amazing what 20-30 feet of good quality turfgrass maintained at a slightly higher height than the surrounding area can do to help slow product movement.  Contact me if you are interested in learning more about the concept of buffer areas around bodies of water.

When I’m in discussion with clients on this issue, it often boils down to a point-blank question from them;  what would I do?  On this particular day, I’ll just say I would not buy my fertilizer yet.  Based what I’m seeing and reading, the storms could come on hard and fast.  Now, if we get a bit of rain to moisten the surface with more in the forecast, then I would probably go ahead and apply fertilizer later this week.  As I said, it depends.