Can I apply fertilizer in winter? (ASK Around)

When you get your results back from a SoilKit test, you'll see a section called "Treatment Recommendation" that breaks down the amendments your soil needs into recommended applications for each season of the year: Spring (March-May), Summer (June-August), Autumn (September-November), and Winter (December-February). Depending on your location, you may be scratching your head to see any recommendations in the winter months. If most plants are dormant or dead, what use is a fertilizer application? Or what if the ground is covered in snow? The answer to this question will depend on your region and local regulations.

The first thing to do is to check your state/local regulations for seasonal restrictions on fertilizer applications. Many regions actually prohibit NPK lawn fertilizer applications during the winter months, although the exact dates vary. This can be due to heavy rain or snow in your area that poses an increased risk of fertilizer being washed away and polluting the environment without your yard having a chance to benefit from it. Nothing to fear from these guidelines--your plants aren't missing out by you waiting for a more opportune time to provide needed nutrients! Plus, fertilizers have a long shelf life, so you'll be able to store them easily in the meantime. Regardless of legal status, you will want to avoid applying fertilizer when there is snow on the ground or when the ground is consistently frozen solid. "Winter" fertilizer application in these cases would be done in late fall, to strengthen roots before plants go dormant. 

On the other hand, if you live in an area with milder winters where winter fertilizers are not restricted, the basic idea to understand winter fertilizer recommendations is to think long term. We asked for some expert advice from farm manager Raul Moto on applying phosphorus (P) fertilizer in cold weather. He said,

"It's beneficial through winter, although uptake will be slow. Unused P will remain in soil and will be immediately available as soon as it comes put of dormancy." -- Raul Moto, Woerner Farms Manager in Roggen, CO

To generalize, winter fertilizer applications are about restoring the soil's nutrient levels in preparation for spring green up, even if plants aren't actively growing at the moment of application. Most nutrients will be stored safely in the soil until they are needed. (The biggest exception is nitrogen, which SoilKit does not recommend for winter aplications.) To minimize loss of nutrients, check your local weather forcast and chose a time to apply fertilizers when no heavy rains are expected for several days.