Perhaps the most important component of a lawn, and often the most ignored, is the stuff it’s grown in. But please don’t call it dirt. Dirt is what you get on your clothes and what you sweep up off the floor. Soil is the proper term for the complex collection of minerals, water, air, organic matter and microscopic organisms that we walk over every day. It’s understandable that folks might tend to ignore this crucial part of lawn care. It’s hard to observe, difficult to control and slow to amend. That’s why it’s so important to consider your existing soil conditions before establishing a lawn. By knowing how different soil types influence lawn grass, you can anticipate potential problems and even begin correcting them.
As many gardeners know, soil is made up of particles that can be divided into three categories, or textures – sand, silt and clay. The size of the soil particle determines what texture it belongs to. The smallest particles belong to the clay category, while sand contains the largest particles. Silt particles are larger than clay, but smaller than sand. Your soil structure is determined by the percentages of each of these textures. Remember the soil texture triangle from school? This handy little diagram is a general guide to figuring out what type of soil you have. Don’t know what your soil texture is? A soil test is an easy way to find out. These tests are available from your local Cooperative Extension Service.
Excessively sandy soils are tricky for growing lawn grass. Sandy soils have a tough time retaining moisture since water drains from them quickly. They can also be low in fertility. To make matters worse, any remaining nutrients tend to get washed away as more water is applied to keep grass green in sandy soil. But it is possible to have a nice looking lawn in these conditions. First, select a grass type that is more tolerant of sandy conditions. In cool northern climates, fescues are the best choice. These consist of the fine fescues, including sheep fescue, and turf-type tall fescue. For warm southern areas of the country, bermudagrass, zoysia, and bahiagrass are all tolerant of sandy soils. You can also improve the structure of sandy soils by applying compost, aged manure and slow-release organic fertilizers regularly. Organic matter increases the moisture holding capacity of sandy soils, as well as the nutrient content. Also, never try to amend sandy soil with clay. This will result in a concrete-like soil structure and is probably one of the worst things you could do to your soil.
Soils with excessive amounts of clay pose other challenges. Unlike sand, clay soils can lack adequate pore space. These pore spaces play an important role in moving water and air within the soil, as well as allowing roots to reach their full potential. A lawn in clay soil could literally be suffocating! Compaction, drainage problems and nutrient deficiencies are also common in heavy clay soils. If you know the soil in your yard contains a lot of clay, choose a grass that can tolerate it. Tall fescue is the best cool-season grass for clay soils, while bermudagrass and buffalograss are the best warm-season grasses for clay. Clay soils can be amended with regular applications of organic matter and/or compost and annual core aeration. Be sure not to work clay soils when they are wet.
Silty soils tend to have the fewest problems. They drain better than clay soils, but retain moisture better than sand. Soils high in silt are often naturally higher in fertility as well. However, they can still experience many of the same problems associated with clay and sand. Applications of organic matter, as well as regular core aeration, are always a good idea for improving silt soils.