Problems with Unrotted Wood Products in Soil
Question from Danielle:
All my vegetable leaves are turning yellow. I filled my raised beds with bagged potting soil and I am using my homemade compost and watering with drip. The soil is moist and I’m fertilizing with packaged fertilizer. There don’t seem to be any pests. What could be the problem?
Answer from Pat:
Last year and again this year several gardeners have told me they are having problems similar to those you are having with yellow leaves on vegetables that were growing in bagged potting soils or in garden soils to which large amounts of bagged wood-based soil amendment had been added. I have written answers to these questions elsewhere on this blog and suggested increased nitrogen might solve the problem. Blood meal is a fast-acting organic nitrogen source. (Please see the Fertilizer chart on this blog for additional ideas.)
Since every audience I speak to had a few folks with this problem, it seemed to me that perhaps the potting soils being sold right now and also some of the bagged, wood-based, soil amendments that are labeled “composted and organic” don’t have enough nitrogen in them. Also perhaps folks aren’t aging their compost enough, so I asked our Farm Advisor what he thought about this problem. Here is his reply:
“Pat,
Yes. Wood-base soil amendment products that are not adequately composted will draw nitrogen from the soil as they decompose. Some products are “nitrolized” and some nitrogen fertilizer (usually a chemical form) is added to the raw wood shavings, sawdust, etc. This provides some nitrogen to offset what is used when the wood product decomposes, but it may not always be enough. It may help crop growth if a slow release form of nitrogen (organic or chemical) is mixed into the soil with amendments that are raw or not adequately composted. When crops are growing rapidly there may not be enough nitrogen to supply their needs and the needs of bacteria and fungi that decompose organic matter, especially if it is not adequately composted.
Vince”