ECO-3 Protecting Our Soil, Water & Air
Erosion & Sediment Control Training & Site Supervision
|
ECO-3 Protecting Our Soil, Water & Air Erosion & Sediment Control Training & Site Supervision
|
|
|
Soil Preparation for Drought Resistance, Increasing Infiltration & Minimizing Runoff Soil preparation is the most important step in providing a drought resistant lawn. It is very important to address the soil condition before the lawn is planted as this cannot be corrected after the lawn is established. The preparation of the soil is the same no matter what method of turf establishment you plan to use. Since grass roots extend 12 to 18 inches in the soil, a two-inch topsoil layer is strictly cosmetic.
Most soil compaction occurs in the top two inches. Breaking through this compacted layer allows water to be absorbed more readily into the soil. Compared to two inches of topsoil, rototilling the existing soil with 1" of organics, results in three times as much growing medium, six inches rather than two, with a 60% cost savings and 75% improved moisture retention. Adding Organics Existing soils can be upgraded by incorporating a topsoil mix or organic material into the soil. Good sources of organic material are rotted manure, compost, humus or mushroom compost. Rototilling these components creates a transition layer of soil. This transition layer is similar in soil composition to the soil below it with a 15% to 20% organic content. This will encourage a deeper root system and produce a better, more drought resistant lawn. Upgrading the existing soil is also a better investment for a long term lawn. Providing the transition soil avoids the typical separation of soil layer problems of shallow roots, root rot, crane fly infestation and fertility problems.
The upgrading of sandy soils will help improve moisture and nutrient retention resulting in lower fertilization costs and watering requirements. In clay soils, upgrading will improve drainage and eliminate the soil interface problems more prevalent between topsoil and clay. The additional step of adding a lawn and garden gypsum, (pronounced GIP SUM) is recommended. Gypsum helps break up the bonding between the clay particles and helps to improve drainage. A recommended application rate of gypsum is 50 to 100 pounds per 1000 square feet. For best result continue to apply gypsum on an annual basis. DO NOT MIX SAND WITH CLAY SOILS. Remember that Portland Cement is actually clay mixed with sand and gravel in the production of CONCRETE. In extremely rocky soil there is no choice but to import topsoil to cover the existing rocks. If this is the case, a 4-inch minimum is recommended with 6 inches preferred. Topsoil Most topsoil mixes available in the Northwest are constructed soils. Composed of one part sawdust, one part manure, and one part clean screened soil. In some cases the manure portion of the mix is straw or shavings, which is the bedding material used in barns. Soil mixes containing straw should be avoided, as you will be importing a large amount of weed seeds into your soil. Mixes containing shavings should also be avoided because the nitrogen-robbing decomposition process causes premature yellowing of the lawn. Some good sources of organic material are rotted manure, compost, humus or mushroom compost. To improve your soil with organics, you will need approximately 3-1⁄2 to 4 cubic yards of material per 1000 sq. ft. of lawn area. This will provide coverage 1 inch to 11⁄4 inches in depth. When spreading the material in the lawn areas, more is not better. Too much organics in the soil can result in a soft spongy lawn. A 15 to 20% organic content is best. You can accomplish this by rototilling the 1-inch of organics into the top 5 inches of existing soil. Should a topsoil mix be used, 7-8 cubic yards per 1000 sq. ft. of lawn area, a 2 inch layer, is recommended. Incorporate the topsoil into the existing soil as described with the organics. The incorporation of granular lime will add calcium and adjust the soil acidity for turf establishment. On smaller sites it is usually less expensive to add lime than to make the determination as to whether it is actually needed. Granular lime or dolomite lime should be added at the rate of 50 to 100 pounds per 1000 square feet. A rear tine or tractor pulled rototiller should be used for best results. In most cases compaction can be accomplished by backblading with a bulldozer or roller. Do not use a vibratory compactor. If a roller is used for compaction, the surface should be machine raked, to loosen the top one inch of soil. Home owners who are performing the work themselves, should saturate the soil with a sprinkler, wait until the soil is firm but still damp, then roll with a water-filled roller to settle. The final step should be to pass a 3-foot landscape rake to loosen the top 1" of soil. Lime addition of lime to the soil improves soil structure and raises the soil pH. Most soils in the Pacific Northwest are within limits for healthy lawn growth. Many times, on small residential or commercial sites, it is less expensive to apply the lime (50-100 pounds per 1000 square feet), than it is to do a soil test. Even if the soil was in the proper pH range, the lawn will still benefit from the improved soil structure and increased availability of calcium. FERTILIZERS Fertilizers play a vital role in keeping turfgrasses beautiful, useful, and free from weeds as well as insect and disease damage. Turf will not develop normally if even one nutrient is deficient. An attractive and serviceable lawn is the result of proper management. Fertility management is probably the most important factor for the development of a good lawn. There are 16 plant food elements required for normal growth of grasses. Three of these, carbon, hydrogen, and oxygen, are obtained from the atmosphere and water, while the other 13 must be supplied by the soil. Nitrogen, phosphorus, and potassium are sometimes referred to as major plant food elements and are needed in relatively large amounts. Calcium and magnesium (supplied by lime and dolomitic lime, respectively), and sulfur are sometimes called “secondary” elements and are intermediate in their requirements. Iron, boron, manganese, copper, zinc, molybdenum, and chlorine, known as minor elements or micronutrients, are required in very small amounts. If any of these last 13 elements are deficient in the soil, they can be supplied from commercial fertilizer sources. Same Ratio/ Different Price A complete fertilizer contains nitrogen (N), phosphorus (P), and potash (K). The percent of each fertilizer nutrient is shown on the bag. An example is 18 - 3 - 9, this bag will contain 18 percent nitrogen, 3 percent phosphorus, and 9 percent potassium (potash) by weight. The difference in cost is most influenced by what source of nitrogen is used. There are two types of nitrogen sources, water soluble and water insoluble. On the label it will state what source the nitrogen is from. Water soluble sources of nitrogen are the fastest acting because they are immediately available to the plant, but do not last very long. An application from a water soluble source may work in as little as two days, but last only two weeks. The most common water soluble sources of nitrogen are ammonium sulfate and ammonium phosphates. They are also the least expensive. The water insoluble sources, such as sulfur coated urea (SCU) or Urea Formaldehyde (UF), do not dissolve as quickly and are classified as slow release forms of nitrogen. These are about 5 times more expensive than water soluble sources, but a single application may last as long as 3 months.
When comparing prices of fertilizers, calculate the cost per
pound of nitrogen. If you have a 50 pound bag of 18 - 3 - 9 that costs $15.00,
your cost is $1.67 per pound of nitrogen: 50lbs. x .18% = 9 pounds of nitrogen
in a 50 lb. bag. $15.00 ÷ 9 lbs.= $1.67/pound. Water solubles (inorganic) are
cheaper per pound of nitrogen versus the water insoluble. A bag of 18 - 3 - 9
with ammonium sulfate as its nitrogen source will be much cheaper than a 18 - 3
- 9 bag where the nitrogen comes from SCU or UF. Use the cost per pound of
nitrogen when comparing similar fertilizer products. Nitrogen, phosphorus, and potassium are all needed in the largest amounts. Nitrogen is utilized the most for the healthy production of leaves and top growth. Rates of nitrogen here in the Pacific Northwest vary from 4 to 6 pounds of nitrogen per 1000 square feet per year, applied in one pound applications. Sandier soils tend to require more nitrogen than a clay type soil due to excess leaching in sandy soils. For new lawns an application of one pound/1000 ft2 of fast release, water soluble nitrogen and up to three pounds/1000 ft2 of slow release nitrogen can be applied. A combination of fast and slow release is recommended. The amount of slow release nitrogen is most often determined by budget. However, usually, the cost of a follow up fertilization is more than buying the good stuff in the first place. To determine the amount of Nitrogen (N) per pound of fertilizer, use the following formula: Total pounds times the percent of Nitrogen. Example: 50 lb. bag of 18-3-9 (50 X .18 = 9lbs nitrogen) To determine how much of this fertilizer is needed to apply a specific amount of Nitrogen to each 1000 sq. ft. of lawn, use the following formula: By applying the 5.5 lbs of product to a 1000 ft2 area , your rate would be one pound of nitrogen per 1000 ft2. As a rule, never apply more than 1 pound per 1000 ft2 of water soluble nitrogen at a time because burning may result. Slow release forms of (N) can be applied as high as 3 pounds per 1000 ft2 without burning. Always read the label for directions on application and recommended rates. A complete fertilizer with a ratio of 6(N) - 1(P) - 2(K) with a minimum of 50% of the N water insoluble, is the current Coastal Northwest recommendation. Northwest lawns utilize these three nutrients in this ratio. Spreaders There are basically two types of spreaders, broadcast (hopper type), and drop spreaders. Broadcast spreaders are preferred for fertilizer applications because they allow for a more uniform application and a large area can be covered in a very short time. When using a broadcast type spreader make sure the applicator is moving when opening and closing the spreader to avoid fertilizer spills and burn. Drop spreaders are preferred for applying insecticide and herbicide products. This type of spreader allows for greater control of keeping the application out of shrub beds and off sidewalks. Drop spreaders make it very difficult to apply fertilizer evenly and take a long time to spread equal amounts of product. (See weed section, pg. 10) Striped lawns are the result of trying to spread all the fertilizer in one pass. Use a criss-cross pattern with the spreader setting at 1/2 the recommended amount. |
Copyright © 2002
ECO-3
|
