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Sod
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Sod or turf is grass and the part of the soil beneath it held together by the roots, or a piece of this material.
The term sod may be used to mean turf grown and cut specifically for the establishment of lawns. However, in British English such material is more usually known as turf, and the word "sod" is limited mainly to agricultural senses (for example for turf when ploughed), or avoided altogether, due to the alternative offensive meaning of the word "sod".
Sod (or turf) for lawns is grown on specialist farms. It is usually grown locally to avoid long transport and drying out and heat buildup of the product.
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Sod or turf is grass and the part of the soil beneath it held together by the roots, or a piece of this material.
The term sod may be used to mean turf grown and cut specifically for the establishment of lawns. However, in British English such material is more usually known as turf, and the word "sod" is limited mainly to agricultural senses (for example for turf when ploughed), or avoided altogether, due to the alternative offensive meaning of the word "sod".
Sod (or turf) for lawns is grown on specialist farms. It is usually grown locally to avoid long transport and drying out and heat buildup of the product. It is sold to landscapers, home builders or home owners who use it to establish a lawn quickly and avoid soil erosion. The farms that produce this grass may have many varieties of grass grown in one location to best suit the consumer's use and preference of appearance. It is usually harvested 10 to 18 months after planting. On the farm it undergoes fertilization, frequent watering, frequent mowing and subsequent vacuuming to remove the clippings. It is harvested using specialized equipment, precision cut to standardized sizes. Sod is typically harvested in small square slabs, rolled rectangles, or large 4-foot wide rolls. Some large sod farms may export internationally. Because of the product's short life after harvest, the sod may be washed clean of the soil down to the bare roots (or sprigs) which makes shipping lighter and cheaper. Sod can be used to repair a small area of lawn that has died.
Sodding vs. Seeding
Seed may be blown about by the wind, eaten by birds, or fail due to drought. It takes some weeks to form a visually appealing lawn, and further time before it is robust enough for use.
Turf largely avoids these problems, and with proper care, newly laid sod is usually fully functional within 30 days of installation and its root system is comparable to that of a seeding lawn two or three years older.
Turf is however more expensive, and requires considerably more water for its establishment.
Erosion after seeding may be a concern in some areas near water. Sod reduces erosion by stabilizing the soil in these type of areas.
Cost
Different types of sod will have different pricing. The availability of sod grasses is generally dependent on where the lawn is located climate-wise. For the United States, landscapers in the northern states will generally sod a lawn with either Kentucky bluegrass or tall fescue (Festuca arundinacea).Kentucky bluegrass has a nice deep green color to it, while tall fescue though not as deep green is excellent for areas that receive medium to heavy traffic since it can resist a lot of abuse. The best, some claim, is a compromise between the two, namely, a grass mixture. Mixtures are also preferred for another reason: disease. "Most [grass] diseases will only strike one type of grass, so the damage will probably be limited [when the lawn was built based on a grass mixture]." Mixed grass sod is sold containing a percentage of Kentucky bluegrass, tall fescue, and/or ryegrass to fill this need.
Tilling technique
Using this method the existing lawn is first tilled (rotovated) thoroughly before the sod is applied There are two variations of the tiller technique.
In the first variation, called the tiller-to-the-grass technique, only the top grass is tilled off and the tilled grass is hauled away leaving just soil on which to apply the sod – no grass remains. The remaining soil may be retilled. This creates a smooth and loose bed on which to install the sod. Some landscapers prefer this smooth and loose bed.
In the second variation, called the till-it-all technique, existing grass as well as the soil underneath holding the grass are tilled together. The old grass is in effect mixed in with the existing soil creating the surface on which the sod will be installed. Some landscapers prefer this method because it creates the bed on which the sod is installed upfront and without further effort.
Some prefer not to use a tiller to prepare the area to be sodded. They claim that if a neighbor or children were to walk over the newly established sod in the first few days after the installation, the turf would become uneven. The claim is that the soil underneath is still very loose.
Herbicide application
This technique involves the application of a herbicide to the existing lawn prior to applying the sod. The chemical kills the existing lawn thoroughly within seven to ten days. The landscaper then simply rakes off the dead grass and disposes of it, leaving nothing but plain soil in the area to be sodded. If the soil left behind is not of high quality, a layer or two of top soil may be applied prior to the installation of the sod. The soil is then nicely graded and the sod is installed on top of it.
Application over the existing lawn
With this technique, sod is simply installed over the existing lawn. Since the existing grass is blocked from receiving sunlight, it starts to die within a few days. Sod can be applied over an existing lawn without much concern about the existing grass underneath – it decomposes and becomes fertilizer for the new sod on top of it. This type of sod installation generally costs significantly less than others, since there is no need to haul away the old lawn. When applying over existing lawn it is preferred, though by no means necessary, to remove a strip about four inches wide by two inches deep of the existing lawn beside the edges of sidewalks and other hardscape structures, to reduce the level of the new lawn somewhat at these points, thus concealing the edges of the newly laid turf.
Some don't like this technique out of concern that any weeds that existed in the previous lawn may remain to affect the new lawn. Also some fear that the existing lawn will need to be aerated so the roots of the sod will have somewhere to "catch" on to. However, the technique is used with equally successful results, or better, as the other three sod application methods.
Post Installation Care
Fertilizer
Immediately after sod has been applied, it is important to fertilize it so as to give it a good, robust start. When applying sod, application of starter fertilizer with a 1-1-1 ratio of Nitrogen, Phosphorus, and Potassium may be recommended. The Phosphorus will assist with root development which is important for the successful establishment of sod. Lightly raking the fertilizer into the soil will help minimize the fertilizer from coming in contact directly with the roots and causing possible root burning. When applying sod to slopes, it is best to lay the sod perpendicular to the direction of the slope. This will help prevent rain water from washing out the sod. Sod staples may be applied to hold the sod in place, but are only required on slopes or in ditches. Freshly-installed sod will need regular watering (without over-watering) to encourage the roots to "look" for water on their own and grow into the soil.
Lime and grub killer
For best long-term results, it is important to test the pH of the soil and to apply limestone powder (to the installed sod) if the soil is acidic. Most lawn grasses thrive in 6.0-7.0 pH soil. Root-eating insect larvae may infest the newly-installed turf, and if this happens they can kill the lawn in a week or two. Insecticide may be used to prevent this happening.
Watering
Except in wet weather, newly installed sod will require two waterings per day, for at least three months, and so this technique for lawn establishment is both expensive and wasteful of water. If not watered regularly before the grass has rooted into the soil beneath the turf, the turf may die, either at the edges, in patches, or overall. Constant care and inspection is required during the first year after installation.
As a Building Material
Sod has occasionally been cut out in blocks to use as a building material, especially in grasslands where grass is plentiful and few other materials are available. For use as a building material, sods are cut out in regular block shapes and laid like brickwork, although for strength blocks of sod are usually much longer and wider than typical bricks. This construction was common during nineteenth century settlements of the Canadian and American prairies. Common dimensions of sod blocks used in these pioneer abodes were 2 ft by 1 ft by 6 in (600 × 300 × 150 mm). Cutting sods for building may be done with a spade and axe, but for large scale work a modified plough is used.
The bare sod is prone to damage from rain or being knocked down, so the outer walls are usually protected with a layer of stucco or wood paneling. Similarly, bare sod inside is dirty, so the interior may be lined with canvas, tarpaper, or plaster. A variety of roofing methods can be used, and the house can be fitted with conventional windows and doors. Sod houses have the advantages of being very cheap, and well insulated, so that they are cool in summer and warm in winter. The main disadvantages are that they tend to be damp, and deteriorate quickly unless maintained.
Sod has also been used in fortification. Blockhouses have been constructed from sod, and it has also been used to make very effective berms or low defensive walls. The Roman-built Antonine Wall in Scotland was largely made from sod.
Because of its cheapness and availability, sod walls could easily be made thick enough to be bulletproof.
See also
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