Woodchips as Mulch - Knowledgebase Question

Orono, ON
Question by klaassch
May 18, 1999
Will a mulch consisting of woodchips (cedar chips) etc. deplete the soil of nitrogen? If true, what do I do to replace the loss of nitrogen?

Answer from NGA
May 18, 1999


Yes, wood chips are high in carbon, so as the microorganisms decompose them, they temporarily rob the soil of nitrogen. As the microorganisms die off, the nitrogen is replaced. (That's a pretty simplified version of some amazing reactions!) However, recent research has shown that when used as a surface mulch, rather than mixed into the soil, the effect of wood chips on soil nitrogen is minimal. Mixed with high nitrogen sources, such as grass clippings, manure, fresh landscape trimmings, vegetable and fruit peelings, etc., it would make a terrific compost that you could use anywhere. Another alternative would be to lay down several inches of grass clippings and put the wood chips on top. Thanks for writing!

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