Turfgrass maintenance problems often result from poor planning in the initial stages of establishment. Poor drainage, scalping and turf-susceptibility to environmental stresses may be the consequence of poor establishment techniques. To ensure a healthy turf and avoid later maintenance problems, begin with proper site preparation. The primary objectives of soil preparation are:
- To provide a firm, smooth surface for rapid establishment
- To provide a rooting medium conducive to water infiltration, aeration and drainage.
The goal of proper site preparation is to create a firm foundation on which you can establish and maintain a high-quality turf with a minimum of difficulty.
The steps for preparing the site are the same whether you establish turf by seed or vegetative methods.
Clear the site. Begin by removing any obstructions that may impede turf establishment and make future maintenance difficult. These include rocks, boulders, old building foundations, roots of dead trees, brush and weeds. When planted over shallow rock outcrops, boulders or old foundations, the turf will have a restricted root system, and it will continually suffer from drought stress. Either remove the obstructions or bury them at least 15 inches deep.
Trees can excessively shade a site. This may prevent good turf establishment and lead to turf thinning. Trees also may reduce air circulation and create an environment conducive to disease development. So selectively prune tree limbs to let in light and promote air movement before establishing turf.
Trees and turf also compete for nutrients and water. In some cases, you may have to remove trees that interfere with the turf and the site’s planned uses. If so, be sure to remove stumps. Don’t simply bury them. As they decompose, the soil will sink. Eventually, a depression will form at the site. Fairy-ring disease also is likely to develop on the excess organic debris.
If you don’t remove difficult-to-control weeds from the site before establishment, you can expect serious persistent problems in the turf. Propagules—seeds, rhizomes, stolons—let the weeds survive tillage and later infest turf. You’ll especially have problems from annual bluegrass seed, quackgrass rhizomes and nutsedge nutlets.
Test the soil. The best way to determine lime and fertilizer requirements is with a soil test. By testing the soil, you can avoid spending unnecessary time, labor and money on materials that the soil doesn’t need. You also avoid applying excessive amounts of lime and nutrients, which could be detrimental to the future turf.
Rough grade and install drainage and irrigation systems. Rough grading involves removing the topsoil and contouring the subgrade. By smoothing out surface irregularities, such as steep slopes and depressions, you will greatly ease future maintenance. Steep slopes interfere with mowing and make applying fertilizer and pesticides difficult. Irrigation also is difficult on slopes. Water often runs off before it can infiltrate the surface. If steep slopes face south, turf can suffer from heat and drought stress.
When determining the contour, consider surface drainage. If the area will be heavily trafficked, contour the site so surface water can run off compacted areas. With home sites should slope away from the house to keep water out of basements.
After contouring the subgrade, replace the topsoil, spreading it evenly over the site. You may have to haul in topsoil from offsite if the existing material is insufficient. Staking the area with markers showing the desired final elevation eases this operation. Topsoil settles after you spread it over the site. You can expect fine-textured soils to settle 5 to 10 percent. Coarse-textured soils won’t settle as much. When marking the stakes, take this settling into account and mark them above the final settling level.
When filling areas with large amounts of topsoil, add the soil in 12-inch-deep layers, rolling between each one to speed settling. If the subsoil is considerably different than the topsoil, mix 2 inches of fill with 2 inches of subsoil to create a transition zone. Using soil amendments, modify topsoil that has a poor texture. Otherwise, the poor texture allows either compaction or poor nutrient and water retention.
Sandy soils don’t hold water or nutrients well. You can improve sandy soils by amending with organic materials or with calcined clay. These materials aid moisture retention and increase cation-exchange capacity, minimizing nutrient loss.
Organic amendments such as peat and compost work well. Because soil microbes break down organic matter, it is important to consider the stability of the material when choosing an organic amendment. Stable materials that resist decomposition will retain their soil-amending properties longer than materials that quickly decompose. If soil nitrogen is low, the turf could become deficient. Reedsedge peat is the most stable peat and is the preferred organic material for turf establishment.
You also can use coarse inorganic amendments for improving the structure of fine-textured, easily compacted soils. Sand is the most widely used inorganic amendment. Another material that is good for this purpose is calcined clay. Not only does it improve soil texture, it also increases cation-exchange capacity and water retention. Calcined clay costs more to use than sand. Isolite is another inorganic amendment that shows promise. Research indicates that it improves aeration in heavy soils and aids water retention.
Characteristics of a good coarse amendment include particle size, particle-size uniformity and durability of the material. The objective of using a coarse amendment is to create large pores in the soil. Sands that are too fine or that are composed of a wide range of particle sizes may actually impede water movement. Coarse amendments that are not durable break up under traffic and lose their beneficial characteristics. For this reason, avoid materials such as vermiculite, perlite and diatomite. Because large pores are important in soil-water movement, you must add enough coarse amendment that individual particles bridge, or touch, each other. The amendment may need to make up as much as 80 to 90 percent of the volume of the soil mixture.
Finish grading will provide a smooth, firm seedbed free of obstructions. When the area has settled and the soil is moist—not too wet or too dry—it is ready for finish grading.
Remove stones and other debris that may impede seedling emergence or interfere with future turf maintenance. If you have sufficient staff or the area is small, use hand rakes. Lightweight, broad aluminum or wooden rakes with closely spaced tines are best for removing small stones and smoothing the soil.
To achieve a smooth firm surface, it is best to rake then roll, alternating procedures until footprinting on the soil surface is minimal. A water-ballast roller one-half to three-fourths full is easy to push and is heavy enough to firm the soil.
Apply starter fertilizers. Starter fertilizers supply young, shallow-rooted seedlings with an initial source of nitrogen. A soluble nitrogen source is best because it is readily available to the seedlings or sod roots.
The site is ready to establish with sod or seed. Choosing the proper plant species will result in a higher success rate in lawn establishment. Our knowledge of turfgrass plant species will provide you with the best lawn considering your surrounding environment.
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