Adding Clay/Biochar - Ask Extension
I have acreage that is mostly wooded except a food plot area. That food plot soil consists of mainly sand followed by clay below. I have added organi...
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Adding Clay/Biochar #922817
Asked December 11, 2025, 1:58 PM EST
I have acreage that is mostly wooded except a food plot area. That food plot soil consists of mainly sand followed by clay below. I have added organic material in the past but it doesn't seem to stay in the soil. I till every year to plant my food plots. Would I benefit from adding clay for water retention at the surface? I am also considering biochar to increase productivity. I have had soil tests over the years and all suggest adding organic material but I cannot get it to last more than a year. I am looking for suggestions and/or recommendations. Thank you.
Gladwin County Michigan
Expert Response
Thank you for your question. Soil is a mixture of sand, silt, clay, minerals and organic matter that also contains space for air and water. Higher sand content means more space for air, water and organic matter (OM). OM can be leaves, plant debris, shredded paper, straw, manure, coffee grounds, food scraps, etc.) which decomposes and is consumed by microbes in the soil. More info on organic matter in the attached links:
https://ohioline.osu.edu/factsheet/SAG-16
https://hoke.ces.ncsu.edu/2018/01/gardening-in-sandy-soils-2/
https://pender.ces.ncsu.edu/2022/02/improving-sandy-soils/
Tilling the soil increases the OM decay rate. Adding multiple inches of several kinds of OM annually for multiple years is beneficial. Making some of it more complex material such as wood chips will eventually increase OM by lengthening the decay time but will consume more nitrogen in the process, so more N may need to be added at first.
Getting sufficient OM in the soil will increase its moisture holding capacity. Be careful adding clay to sand, without enough OM you could end up with a poor grade cement-like soil. More o=info here:
https://extension.illinois.edu/blogs/good-growing/2018-01-31-does-sand-improve-clay-soil-drainage
https://extension.usu.edu/yardandgarden/research/gardening-in-sandy-soils
Biochar might be used as a soil amendment to potentially increase yields, improve soil structure, increase water holding capacity, increase pH, increase nutrient absorption and reduce nitrous oxide emissions. I didn't find info on the amount needed per soil type or the cost. Here are some links to articles on biochar:
Biochar Info-MSU
https://extension.psu.edu/biochar-properties-and-potential
https://www.ctahr.hawaii.edu/oc/freepubs/pdf/SCM-30.pdf
https://warren.cce.cornell.edu/gardening-landscape/warren-county-master-gardener-articles/-biochars-and-their-uses-in-agriculture
https://blogs.ifas.ufl.edu/lakeco/2020/05/22/biochar-helps-sandy-soil-support-mycorrhizae/
As a side note, I've added 6" to 10" of leaves to a clay garden for over 2 decade and it's become a clay-loam soil. You can accomplish a similar result with your food plot, creating a sandy-loam by adding lots of OM every year and tilling it in.
https://ohioline.osu.edu/factsheet/SAG-16
https://hoke.ces.ncsu.edu/2018/01/gardening-in-sandy-soils-2/
https://pender.ces.ncsu.edu/2022/02/improving-sandy-soils/
Tilling the soil increases the OM decay rate. Adding multiple inches of several kinds of OM annually for multiple years is beneficial. Making some of it more complex material such as wood chips will eventually increase OM by lengthening the decay time but will consume more nitrogen in the process, so more N may need to be added at first.
Getting sufficient OM in the soil will increase its moisture holding capacity. Be careful adding clay to sand, without enough OM you could end up with a poor grade cement-like soil. More o=info here:
https://extension.illinois.edu/blogs/good-growing/2018-01-31-does-sand-improve-clay-soil-drainage
https://extension.usu.edu/yardandgarden/research/gardening-in-sandy-soils
Biochar might be used as a soil amendment to potentially increase yields, improve soil structure, increase water holding capacity, increase pH, increase nutrient absorption and reduce nitrous oxide emissions. I didn't find info on the amount needed per soil type or the cost. Here are some links to articles on biochar:
Biochar Info-MSU
https://extension.psu.edu/biochar-properties-and-potential
https://www.ctahr.hawaii.edu/oc/freepubs/pdf/SCM-30.pdf
https://warren.cce.cornell.edu/gardening-landscape/warren-county-master-gardener-articles/-biochars-and-their-uses-in-agriculture
https://blogs.ifas.ufl.edu/lakeco/2020/05/22/biochar-helps-sandy-soil-support-mycorrhizae/
As a side note, I've added 6" to 10" of leaves to a clay garden for over 2 decade and it's become a clay-loam soil. You can accomplish a similar result with your food plot, creating a sandy-loam by adding lots of OM every year and tilling it in.
