We would like to put in a new lawn around a home where there were mostly weeds. The soil is very a heavy silt because it is river bottom land. I have access to free sand; however, I’ve heard conflicting advice regarding adding sand to clay — some say yes, others no. I also have access to a large supply of free horse shavings/manure from a horse stable. Would those shavings be good to add to the soil to help lighten it and add nutrients? I don’t want to go to the expense of bringing in topsoil if I don’t have to. What are your suggestions?
Adding sand to clay soil is not recommended as a way of lightening the soil, as it “may create a concrete-like structure”, according to the booklet Ecologically Sound Lawn Care for the Pacific Northwest by David K.
McDonald. Linda Chalker-Scott addresses the reasons for this in depth in “The Myth of Soil Amendments Part II”.
Instead of adding sand, David McDonald recommends trying to till in compost. At least two inches of compost tilled into the upper six to eight inches of soil is recommended, but four inches tilled into the upper twelve inches is preferable . Try to avoid doing this when the soil is waterlogged, as it may damage the soil structure.
Composting the horse manure and shavings you have access to could be a feasible way to obtain the compost to till into the soil. The Guide to Composting Horse Manure by Jessica Paige of Whatcom County WSU Extension discusses how to compost and use horse manure. She recommends curing such compost at least a few weeks before application, and adds that one to three months is a good, typical composting time in summer or three to six months in winter.
Alternatively, according to David McDonald, if there are a few months of warm weather between autumn and seeding time, you could simply till the fall leaves and grass clippings into your soil. Depending on your planned schedule, this could be very easy. (You can find McDonald’s full booklet “Ecologically Sound Lawn Care for the
Pacific Northwest: Findings from the Scientific Literature and Recommendations from Turf Professionals” online as a very large PDF.)
Another option might be to consider some sort of groundcover if you discoverthat establishing a lawn is an excessively extensive project. Carex species or possibly Juncus phaeocephalus phaeocephalus are more naturally adapted to heavy soils in wet areas than lawn grasses and so may be less work in the end. Though they would not be appropriate for a heavy traffic area, they would be grasslike in structure. Sagina subulata might be more amenable to heavy traffic.