Nitrogen loss due to woody compost #703466 - Ask Extension


Nitrogen loss due to woody compost #703466

Asked July 21, 2020, 11:08 AM EDT

I'm developing a .4 acre garden in Afton. I tilled in a fair amount of compost purchased from Gertens. The vegetable plants are not doing well. Gertens compost has lots of wood mulch as a main ingredient. I've read that decomposing wood sucks up a lot of nitrogen, taking it away from plants. Is this true? I have some Fall lawn fertilizer, 30-0-4 with added sulfur and iron. Could I till some of that into the soil this fall to bring N levels up? I have 15 blueberry plants that require acidic soil. Could I use it on those plants this fall?

Washington County Minnesota

Expert Response

If the Gertens product is compost, the ingredients used to create it have already decomposed and will not affect the amount of nitrogen in the soil.

However, because nitrogen is readily leached from the soil, adding some is usually recommended to grow vegetables.  Testing the soil is the best way to determine what amendments, including nitrogen, are needed to create optimum conditions for whatever you plan to grow. Go here to learn how to prepare soil samples and where to send them for testing:

Applying nitrogen to turf in the fall is beneficial but if additional nitrogen is needed in the vegetable garden, it's best to apply it in spring.

Go here to learn how and when to fertilize blueberries:

Go here for information about using wood mulch in and around the garden.

Bob Bystrom Replied July 21, 2020, 1:05 PM EDT

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