Soil test results: reduce pH without tilling? - Ask Extension
Hi, my University of Delaware soil test results indicate a high pH (7.9). The advice given is to till in sulfur. Are there any none-tilling options fo...
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Soil test results: reduce pH without tilling? #895022
Asked March 20, 2025, 11:50 PM EDT
Hi, my University of Delaware soil test results indicate a high pH (7.9). The advice given is to till in sulfur. Are there any none-tilling options for lowering pH? I'm willing to disturb the soil if that's what's necessary to fix the pH. But I can't afford to rent or buy a tiller and I don't think digging with a shovel is a viable option.
I'm trying to make an in-ground vegetable garden from my compacted clay lawn that has never been tilled. It's been sheet-mulched with cardboard and woodchips for a year, which has resulted in a big improvement in the top few inches of soil. But below that it's heavy clay. In some spots it's so rock-hard that I can't even get a sharp shovel into the clay when jumping on the shovel. There's also a lot of willow roots near the surface of the soil, from a very large willow tree on the other side of the yard. So overall, hand-shoveling the 1000-2000 square feet I'm hoping to turn into garden space, would likely take more strength and time than I have available.
I could maybe borrow a broadfork from the tool library but I don't know how/whether a broadfork can be used to incorporate sulphur into the soil. I've never used one, but it doesn't look like it really turns over or mixes things into the soil, just lifts it up a bit.
Would there be any use in adding powdered elemental sulfur on top of the soil (maybe covered with compost or woodchips) without digging/tilling it into the soil?
Would using ammonium sulfate as my choice of nitrogen fertilizer help lower the pH at all?
Also, is there anything that will help achieve pH changes this growing season? From what I've read, elemental sulfur takes 6+ months to be converted to a usable form. So I might not see pH improvements till next year even if I did till in sulfur.
Thanks for your help, I appreciate any advice you can give.
Howard County Maryland
Expert Response
Hi- it sounds like the topsoil was removed during home construction. Compacted high clay soils can make gardening difficult. Count yourself lucky if water drains after storms rather than pooling for hours or days.
There are two types of widely available garden sulfur- elemental sulfur (flowers of sulfur) which is 90% sulfur and iron sulfate which is 12% sulfur. We recommend applying 15 lbs./1,000 sq. ft. of each of these two products. Distribute them as evenly as possible and rake them into the top few inches of soil or compost if possible. Apply them prior to expected rainfall or water them in after the application if rainfall is not expected. It will take approximately one year to drop the pH to around 6.5. Test your soil again in 12-15 months.
The quickest way to improve the soil is by spreading an 8-in. layer of compost or 50:50 topsoil/compost mix. This will also help drop the soil pH. Although the soil pH may not drop much this growing season, your vegetables should do ok.
Yearly additions of compost and planting a fall cover crop will help to improve soil structure. A broadfork can help loosen the clay soil and facilitate movement of organic matter downward.
Lots of shallow tree roots growing into a vegetable garden will make soil preparation and planting difficult and will likely reduce productivity. In that case, you may want to build or buy raised beds and fill them with 12-18 inches of a 50:50 topsoil/compost mix.
https://extension.umd.edu/resource/vegetables-home-garden/
Jon
There are two types of widely available garden sulfur- elemental sulfur (flowers of sulfur) which is 90% sulfur and iron sulfate which is 12% sulfur. We recommend applying 15 lbs./1,000 sq. ft. of each of these two products. Distribute them as evenly as possible and rake them into the top few inches of soil or compost if possible. Apply them prior to expected rainfall or water them in after the application if rainfall is not expected. It will take approximately one year to drop the pH to around 6.5. Test your soil again in 12-15 months.
The quickest way to improve the soil is by spreading an 8-in. layer of compost or 50:50 topsoil/compost mix. This will also help drop the soil pH. Although the soil pH may not drop much this growing season, your vegetables should do ok.
Yearly additions of compost and planting a fall cover crop will help to improve soil structure. A broadfork can help loosen the clay soil and facilitate movement of organic matter downward.
Lots of shallow tree roots growing into a vegetable garden will make soil preparation and planting difficult and will likely reduce productivity. In that case, you may want to build or buy raised beds and fill them with 12-18 inches of a 50:50 topsoil/compost mix.
https://extension.umd.edu/resource/vegetables-home-garden/
Jon