How to Enhance Soil for Your Turf Grass

Some nutrients are naturally present in the soil while others come from applied fertilizers—both can either be put to good use or go to waste depending on environmental factors. Most soil nutrients are either immediately absorbed by your grass or stored as reserves in the soil—but a number of outcomes are possible:

1. Plant uptake. The extensive root system and leaf arrangement of turf grass makes the plant extremely efficient at using nutrients. Water and carbon dioxide are absorbed by the leaves (along with some nutrients) while roots soak up the remaining nutrients. Some nutrients gather in soil water near the grass roots, waiting until the plant needs them.
    
2. Soil storage. Although clay soils hold a wealth of nutrients—often far more than plants need for growing—most are locked up in the soil and not available all at once for turf grass growth. As time passes, temperature, water, soil microorganisms and organic matter help release these nutrients for absorption by turf grass root systems. This nutrient-rich reservoir system can be supplemented by fertilizers so that your lawn has more available nutrients at the ready.
    
3. Erosion. The largest contributor to water pollution in the United States is sedimentation. As rain falls, soil particles erode and are suspended in water to be carried away—nutrients and all. Phosphorus is the primary nutrient carried away by soil erosion, but all are susceptible. High rainfall increases the chances that nutrient-rich soil will be moved off-site. Turf grass remains one of the best water filtration systems and significantly reduces soil erosion.
    
4. Leaching. The leaching of soluble nutrients from the root zone can occur from heavy rainfall and over-application. This risk is increased in sandy soils. Under these poor conditions, vital nutrients, such as potassium and nitrogen, are often lost to leaching.
    
5. Volatilization. Nutrients can be lost to the atmosphere through a process called volatilization. Liquid- and granular-applied water-soluble fertilizers are both susceptible to volatilization, with nitrogen being the primary nutrient lost.

For turf grass management in soils with a pH level below 6.2, lime plays an important role. These types of acidic soils are typically found in the Pacific Northwest, along the East Coast, in certain southeastern states and among the Appalachian Mountains. While you can apply lime at any time, fall is the recommended time for application so that the lime has all winter to break down in time for next growing season.

The benefits of lime for turf grass include:

• Correcting soil acidity
• Replenishing vital plant nutrients such as magnesium and calcium
• Increasing bacterial activity and aid for soil structure
• Reducing solubility and toxicity of elements including aluminum, manganese and iron
• Adding soil-regulating calcium, which nurtures a desirable range of plant nutrient availability in zinc, copper and phosphorus

The type of lime you use to bring out your lawn’s full potential can come from a few sources:

• Calcium carbonate (CaCO3) comes from calcitic lime, which is ground up agricultural limestone that’s mined from natural limestone bedrock. It can be dusty to apply.
• Pelletized lime is made by finely grinding agricultural lime and then adding a cementing agent to form pellets. These pellets make application less dusty and turf grass management much easier.
• Dolomitic limestone contains nearly equal parts of magnesium and calcium carbonate and is used along the East Coast.

Calcium sulfate—also known as gypsum—is rarely used on turf grass in most regions of the United States. But for the sodic soils and soils with a high pH level found in the western and southwestern parts of the country, gypsum reduces the toxic effect of sodium and helps it leach from root zones. Before using gypsum, test your soil for soluble salt levels to see if this nutrient will help.

Another example is late-fall fertilization. This takes advantage of a time when shoot growth is slowing but root growth is still happening. Plus, applying nitrogen to your lawn in the fall significantly boosts the production of carbohydrates, which are stored up for the next growing season. This improves your chances of enjoying an early spring green-up.

In order to increase the availability of micronutrients and calcium in alkaline soils—soils with a pH level above 7.8—sulfur applications can be used. By lowering the pH level, iron and manganese will specifically become more available.

Soil tests should be performed before application to see if sulfur will be beneficial—not all lawns will react to sulfur.  You can increase your chances of lowering pH levels by applying in the spring or fall along with core cultivation. Soil reacts slowly to sulfur, so be sure to perform additional soil tests before reapplication.