Water should never be applied at a rate faster than it can be absorbed by the soil. Soil properties that govern water infiltration (movement of water into the soil) are:
- Texture: The size of soil particles
- Structure: The arrangement of soil particles. Soils exhibiting good aggregation (a measure of structure) permit more rapid infiltration of water.
Texture and structure influences not only the infiltration of water, but also water-holding ability and soil drainage.
- Degree of compaction: Compaction refers to a condition in which aggregation is reduced or absent. The degree of compaction at or near the surface is of special importance insofar as infiltration of water is concerned. It has been shown experimentally that a very thin layer of compacted soil will substantially reduce the rate of infiltration.
- Another very important factor that influences the ability of a soil to absorb moisture is the rate at which the water is applied.
Sprinklers that do not adequately disperse moisture, as well as sprinklers that deliver a large volume of water within a concentrated area, tend to cause surface runoff. Whenever water is applied at a rate faster than it may be absorbed by a given soil, the water is being wasted.
Amount of water to apply
The amount of water to apply at any one time will depend upon:
- The water-holding capacity of the soil: The water-holding capacity of the soil will determine how much water will be needed at any one watering. Loams and clay loams are generally considered to have desirable water-holding capacity, whereas sands display very little water-holding capacity.
- The amount of moisture present when irrigation is started: A sufficient amount of moisture should be applied to insure that the entire root zone will be wetted. Once the soil is already wet throughout the root zone any additional water applied will merely fill the large pores and be excess.
- Drainage: Removal of excess water from soils is referred to as drainage. Unless soil is adequately drained, problems can arise because of the slow removal of excess water.
Nutritional Value for the Landscape
Processing lawn clippings and tree leaves into the lawn provides nutritional value as well as reduces waste. Generally, turf clippings contain 6-7% nitrogen, 0.5 to 1.0% phosphorous and 2-4% potassium; when returned to the lawn, they can account for a fourth of the lawn's fertilizer applications each year.
How Much Nitrogen Is Needed?
When calculating how much fertilizer to put on a Kentucky bluegrass or turf-type tall fescue lawn, first consider the desired level of maintenance.
- Low maintenance lawns, apply 1-2 lbs of actual nitrogen per 1,000 sq. ft. per year.
- Medium should receive 2-3 lbs per 1,000 sq. ft.
- High maintenance turfs should receive 3-4 lbs per 1,000 sq. ft.
This amount should be spread out over the year, typically applied in
- late April (Arbor Day),
- early June (Memorial Day),
- early September (Labor Day) and
- early November, (Halloween).
For example, a reasonable schedule for a medium maintenance lawn would be to apply a half pound at each time period for a total of 2 lbs. of nitrogen per 1,000 sq. ft. per growing season. Regardless of the desired manner of maintenance, apply no more than a half pound of nitrogen per 1,000 sq. ft. in the early November application.
For zoysia lawns, apply
- 0.5 lbs in mid-May (Mothers Day) and
- 0.5 lbs in late June or early July (Flag Day or Independence Day).
Use the Fertilizer Ratio to Calculate Pounds of Product to Apply
Next, to determine how much fertilizer product to spread over 1,000 sq. ft. of the lawn, divide the amount desired expressed as a percentage by the concentration of fertilizer product. If 0.5 lbs nitrogen is desirable and the fertilizer analysis is 22-3-4, the division would be 0.5 by 0.22, which equals 2.27 lbs or 2 1/4th pounds of fertilizer product.
Then, measure the lawn area to be fertilized by marking off roughly rectangular areas and multiplying the length and width of each. If the lawn area is determined to be 6,000 sq. ft., multiply 2 1/4th by 6 to determine that 13.5 pounds of the product should be applied to the entire lawn.
Whenever possible, slow release nitrogen fertilizer such as sulfur coated urea, urea formaldehyde, methylene urea, IBDU and plastic coated urea should be applied. These products produce an even greening effect, provide for the nutritional needs of the lawn and greatly reduce the potential for water pollution.
After any fertilizer application, the non-turf surfaces of the landscape such as patios, driveways and sidewalks should be swept or blown off to return product particles to the lawn.