A properly fertilized turf has fewer weeds, is more resistant to insects and disease, and decreases water runoff compared to malnourished turf. Concern over the negative effects of nutrient enrichment on water quality is a growing public concern and has led many to start to question turfgrass fertilization practices. Although both nitrogen and phosphorus may contribute to nutrient enrichment the exact extent of the contribution remains rather uncertain. Current research for turfgrass systems has demonstrated that when turf is fertilized properly (proper rate, appropriate nutrient source and application timing) that those nutrients remain with the turf. Regardless, it is still important to fertilize lawns responsibly. Here are a few tips:
Before applying any fertilizer, insure frequent mowing at 3” or more, return clippings, and use a sharp blade. These simple practices will allow the turf to benfit most from applied fertilizer and recycles nutrients in clippings from year to year.
Apply fertilizer when the turf can use it best: The focus is primarily fall (Sept. - Nov.) for cool-season turf like Kentucky bluegrass and tall fescue as well as modest amounts in the next month (May/June) after the spring growth flush.
Rethink how much fertilizer is applied annually: A very well maintained Kentucky bluegrass lawn will probably require 3.5 to 4.0 lbs N/1000 sq ft/yr. However, reducing that overall amount by 10 to 30% in any given year or two will likely not dramatically affect the appearance or performance of the turf. A very mature lawn where clippings have been regularly returned may still perform well with 25-50% less nitrogen.
Get a soil test! The only way to truly know if nutrients like phosphorus or potassium are necessary is through a soil test. (see link below for more information). Unfortunately, there is no truly reliable soil test for nitrogen.
Select products designed specifically for lawns. Avoid "General purpose/all purpose" fertilizers (e.g. 12-12-12 or 10-10-10 analysis). There are many consumer products designed specifically from lawns (e.g. 28-2-10 analysis). Where no phosphorus is recommended then zero phosphorus products like 28-0-3 should be applied.
Other than when seeding or sodding, limit the amount of phosphorus you apply. Indiana soils generally have ample phosphorus for established turf, but an occasional soil test will dictate your need for phosphorus. Most retailers now carry fertilizers containing little or no phosphorus, which tend to be less expensive than complete fertilizers.
Calibrate your spreader to apply the proper amount and then apply the product uniformly to the lawn (Note: Using a rotary type spreader and applying the product in two perpendicular directions will minimize any green streaks following fertilization).
Water the nutrients into the lawn. This is not always feasible for many home-owners without an in-ground irrigation system, however, moving the nutrients into the rootzone where the turf roots can take up the fertilizer is important.
Avoid spreading fertilizer into water by maintaining a ten foot or more untreated buffer strip around creeks, ponds, etc. This buffer strip should be wider on severely sloped sites.
Avoid spreading fertilizer onto sidewalks or driveways and sweep or blow product back into the turf if this does occur.
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Be sure to purchase the proper amount and type of fertilizer and then apply accurately and evenly (as opposed to this lawn) |
Avoid applying to impermeable surfaces, but be sure to sweep or blow any fertilizer back into the lawn. |
There’s much more information on our web site including:
Complete fertilization and calibration information in “Fertilizing Established Lawns: AY-22” at http://www.agry.purdue.edu/turf/pubs/ay-22.pdf
Fertilizer rate calculator: http://www.agry.purdue.edu/turf/fertcalc/Fertilization%20calc.html
Soil testing information: http://www.agry.purdue.edu/turf/pubs/ay-18.pdf
List of soil testing labs: http://www.agry.purdue.edu/ext/soiltest.html
Fertilization to protect water quality: http://www.agry.purdue.edu/turf/tips/2008/03_21fert.html
Phosphorus fertilization in turf: http://www.agry.purdue.edu/turf/tips/2005/phosp526.htm
Send corrections, suggestions, and comments to biehlj@purdue.edu
