Expert: Greg - 8/28/2007

Question
I want to make an earthen hill across the front of my yard (approx 20' x 60' x 4' high) and plant red cedar and frasier fir saplings (~3 yrs old).  Since hauling in topsoil is rather expensive and I have access to a lot of horse manure and wood chips, can I use them together with some dirt to make the hill?  Is there any long term effects to worry about?  I'm thinking there should be plenty of nitrogen in the manure to allow the chips to decompose.

Answer
Hello Bill

I am going to try and answer your Question in a couple of parts.

First of all, Horse Manure is a Hot Manure, if it is not treated properly, it could be subjected to a process called "Fire Fang". Farmers and Pro's know how to water down the Manure to prevent this from happening. If you have access to a ready supply, it would do you well to read up on the proper procedure for doing this.

You must Compost all of this "BEFORE" you use it in the mix. Mixing it all together without proper Composting will cause issues. Wood Chips take quite a long time to decompose, even with proper Carbon to Nitrogen ratios. The Wood Chips will take Nitrogen to complete the Decomposition process, and they will take it from wherever they can get it, causing a Nitrogen defiency in the soil, the Trees will suffer unless you supplement more Nitrogen.

For the last part, keep in mind that Compost, in itself, over time, will decompose entirely. This means that the level you choose will sink depending on how much Compost is in the Mixture. This will take 3-10 Years, and it will happen fast at first, then quite gradual.

I hope this helps, if I have missed something here, don't hesitate with a follow-up question.

Greg