Oak leaves mixed in with garden soil

Asked November 27, 2017, 10:26 AM EST

My garden consists of clay soil with little organic matter. If I till oak leaves into the soil to add humus, will I change the ph of the soil due to the acidic nature of the oak leaves? If the answer to the question is yes, could I add lime to the soil to reestablish a proper ph? Phil Sutton psutton19@yahoo.com

Jackson County Missouri horticulture

1 Response

One of our lawn and turf specialist wrote an article last year that says you have little to worry about on the soil pH change. I would suggest you look for nitrogen deficiencies, yellowing in plants next spring, just in case the high C:N ratio of the leaves ties up much of the free nitrogen in the soil.

Studies from Michigan State University Extension in the 1990s evaluated the effects of leaf mulching on turf under various conditions. Researchers found that soil pH did not change, but organic matter increased. The percentages of carbon and nitrogen stayed constant.

Garden soil should react much the same way. Consider mowing or chopping the leaves. Whole leaves do not mix well with the soil. With whole leaves, you can end up with wads that block water movement and do not decompose for an extended time. Those wads will also cause dry pockets that block root growth.