Long-Term Effects of Wood Chips on Vegetable Growth

Direct Benefits

• Using wood chips in your vegetable garden has many direct benefits. Wood chips can help improve soil structure and enhance gas transfer, water infiltration and retention. Wood chips can help prevent erosion and compaction and help to moderate fluctuations in temperature. Wood chips often have stems, leaves and twigs mixed in, and the resulting decomposition of these items will increase the nutrient content of the soil. Wood chips are also an environmentally friendly product. They help reduce landfill usage, reduce the carbon footprint by using locally produced chips and are cost effective.

Carbon to Nitrogen Ratio

• It is important to understand that wood chips have a high carbon to nitrogen ratio. Organic components that have this attribute are often discouraged from being used in a vegetable garden. Carbon to nitrogen ratio is the ratio between carbon (dead or brown material) and nitrogen (green or living material) needed for effective decomposition. Examples of carbon-rich materials include wood chips, newspapers, twigs and other paper materials. Examples of nitrogen-rich materials include grass clippings, leaves and food scraps. When a product has a high ratio, the breakdown of that material is very slow. Wood chips come highly recommended in landscape applications for this very reason. However, in the vegetable garden, the chips could make bed preparation more difficult in the following years.

Long-Term Effects

• With a high carbon to nitrogen ratio, the long-term effects of wood chips in the vegetable garden can include a reduction of nitrogen at the mulch and soil interface. As the wood chips start to decompose, the nitrogen in the very top layer of soil will be used up in the process, reducing the available nutrients for shallow-rooted plants such as vegetables. If wood chips are to be used, try the "mulch sandwich" method. Before applying the wood chips, spread a thin layer of nutrient-rich compost on top of your soil, then lay down your wood chips on top.

Recommended Mulches

• Many other types of mulches are recommended for short-term use in a vegetable garden. Some organic mulches to use include hay or straw, grass clippings and chopped leaves. Place organic mulches no more than 2 to 3 inches thick. Inorganic mulches that work well in the vegetable garden include black, clear or red plastics or a layer of three to four newspapers.