Lawn fertilizer best practices
Applying the right fertilizer, in the right amount, at the right time of year has numerous benefits:
1. Your lawn will be green and healthy.
2. You’ll save money by not over-fertilizing.
3. You’ll protect the bay and its fisheries from excess fertilizer runoff that reduces water quality and clarity.
It’s up to all of us to do our part by adhering to the following Lawn Fertilizer Best Practices.
Lawn fertilizer is a significant source of nutrients (especially nitrogen) contributing to reduced water quality in Duxbury Bay. The information below is intended to provide landscape professionals and homeowners science-based guidelines for fertilizer use and other landscape practices that, when followed, reduce the loss of soil nutrients from excessive, incorrectly timed, or inappropriate fertilizers. In Duxbury, lost nutrients find their way rapidly to the coastal waters, harbors, ponds, and streams where they may cause contamination that is harmful to aquatic organisms as well as to human health and welfare.
Timing is everything: Guidelines for Timing and Rates for Application of Turfgrass Fertilizer
• Effective and safe turf fertilizer use depends on correct application rates and timing.
• A soil test analysis should be consulted for making informed fertilizer application decisions.
• Fertilizer, both synthetic and organic, including composts, should only be applied after April 15 and before October 15 and when soil temperatures are above 55° F.
• Fertilizers should not be applied before a heavy rain and irrigation after application is limited to moistening the root zone.
• The nitrogen [N] application rate for lawns in Duxbury should be no more than 3 lbs. N/1000 /sq. ft. /year.
• No individual N application should exceed 1 lb. N/1000 sq. ft .
• No individual N application should contain more than 0.25 lbs fast-release N/1000 sq. ft.
• Timing for N applications intervals depends on the amount of N per application and should never be less than two weeks apart.
• Observation of turf color and vigor should help guide application intervals over the course of the growing season.
• Phosphorus [P] should not be applied unless a soil test indicates a deficiency. Detailed exceptions are made for compost.
• Spoon-feeding of smaller amounts of fertilizer at more frequent intervals is often the most efficient and safe way to fertilize but may not be realistic for most applicators or homeowners.
Fertility Programs
Three sample fertility programs are detailed below: An organic approach, a synthetic approach, and a hybrid (combined organic and synthetic) approach for annual turf fertilization. These programs are outlined in the “Best Management Practices for Landscape Fertilizer Use on Nantucket Island” by the Article 68 Work Group in 2010-2012, Nantucket, MA. The full document is available for download at Nantucket-ma.gov.
Organic Fertility Program ↓
Synthetic Fertility Program ↓
Hybrid Fertilizer Program – Spoon-Feeding ↓
Organic Fertility Program ↓
This program is designed for renovation of a homeowner-maintained lawn that is under performing.
The soil-analysis identified pH at 5.3, “optimum” P content, “very low” K content, “low” magnesium [Mg] and OM at 3.4 %.
- First application: Apply dolomitic limestone as indicated by the soil test at rates up to 50 lbs./1000 sq. ft. to raise pH and improve Mg levels in late fall of the previous season, when possible, as lime takes up to six months to alter pH.
- Second application: As soil temperatures reach 55° F in spring (late April to mid-May), apply natural sulfate of potash (0-0-50) at 1 lb./1000 sq. ft. of K₂O to improve K levels. Apply sulfate of potash, magnesia at 0.5 lb./1000 sq. ft. of K₂O to improve K, Mg, and sulfur. Alternatively, use dolomitic limestone in the step above to alter Mg content if needed. Top-dress with leaf-litter compost at a ⅛″depth to increase the soil’s OM level, supply a small amount of N (0.3 lbs N/1000 sq. ft.) and increase soil microbiology.
- Third application, June 15. Apply an organic fertilizer blend of 6-0-6, at the rate of 1 lb. N/1000 sq. ft. A typical organic blend of 6-0-6 is made from sulfate of potash, natural nitrate of soda, peanut meal, feather meal, and pasteurized poultry litter. 75% of the N is water insoluble, or slow release.
- Fourth application, July 15. Apply compost tea to supply beneficial microorganisms, micro elements, and less than 0.1 lb. N/1000 sq. ft.
- Fifth application, Aug 15. Apply compost tea to supply beneficial microorganisms, micro elements, and less than 0.1 lb. N/1000 sq. ft.
- Sixth application, Sept 1. Top-dress with leaf-litter compost at a 1⁄8″ depth to increase soil OM, N (est. 0.3 lb. N/1000 sq. ft.) and microbiology. Combine this application with aeration and over seeding to increase turf density.
- Seventh application, Sept 15. Apply the 6-0-6 organic blend as described in the Third Appliction, at a rate of 1 lb. N/1000 sq. ft.
- Eighth application, Oct 1. If the need is indicated by a subsequent soil test, apply natural sulfate of potash (0-0-50) at a rate of 1 lb. K/1000 sq. ft. K₂O to improve K levels.
Totals for the season:
N – 2.8 lb./1000 sq. ft.
P (from leaf-based compost) – 0.45 lbs P₂O₅/1000 sq. ft. K – 4.5 lbs. K₂O/1000 sq. ft.
Sulfur – 0.5 lb./1000 sq. ft. Mg – 0.5 lb per 1000 sq ft.
Find this program on page 31 of “Best Management Practices for Landscape Fertilizer Use on Nantucket Island” by the Article 68 Work Group in 2010-2012, Nantucket, MA.
Synthetic Fertility Program ↓
The following program consists of products that contain primarily synthetic sources of N. It presumes a relatively healthy irrigated turf with sufficient phosphorus available in the soil.
- First application, late fall of previous season. Application of dolomitic limestone at 50 lbs./1000 sq. ft. to raise pH and improve Mg levels in late fall of the previous season, if possible, as lime takes up to six months to alter pH
- Second application, May 15. Apply 30-0-7 with 75% slow-release N, at a rate of 1 lb. actual N/1000 sq. ft.
- Third application, July 1. Apply (15-0-8) an organic/synthetic bridge product with 92% slow-release N, at a rate of 1 lb. actual N/1000 sq. ft.
- Fourth application, Aug 15. Apply a synthetic fertilizer (29-0-10) with 70 % slow-release N at the rate of 0.5 lb. actual N/1000 sq. ft.
- Fifth application, Oct 1. Apply (15-0-8) an organic/synthetic bridge product at the rate of 0.5 lb. actual N/1000 sq. ft.
Totals for the season:
N – 3.00 lbs./1000 sq. ft., 83% of which is slow release and 40% organic
P – 0.0 lbs.P₂O₅ /1000 sq. ft.
K– 1.2 lbs. K₂O/1000 sq. ft.
Find this program on page 32 of “Best Management Practices for Landscape Fertilizer Use on Nantucket Island” by the Article 68 Work Group in 2010-2012, Nantucket, MA.
Hybrid Fertilizer Program – Spoon-Feeding ↓
The following turf-fertility program consists of products that contain both organic and synthetic sources of N. The assumption is that P levels are optimum, as indicated by a soil test, and that K is deficient. Some of these products below are “bridge products” that contain both organic and synthetic materials. This program emphasizes the spoon-feeding of N.
- First application, May 14. Apply 6-0-12, at a rate of 0.24 lb. N/1000 sq. ft., 100% fast release. Also contains manganese sulfate (which will provide enhanced green color similar to iron sulfate) and magnesium sulfate to increase Mg levels.
- Second application, June 4. Apply 12-0-12, 0.48 lb.N/1000 sq. ft., 50% slow release. This fertilizer is a bridge product that is 50% organic and 50% synthetic. Urea and methylene urea (slow release) make up the synthetic portion of this product. Organic sources of N include kelp meal, fish meal, crab meal, alfalfa meal, poultry meal, and blood meal. These sources include fast- and slow-release sources of N. A small amount of P is included in this product. It also contains ferrous sulfate for color and magnesium sulfate to increase Mg levels.
- Third application, July 2. Apply 12-0-12, 0.48 lb.N/1000 sq. ft., 50% slow release.
- Fourth application, Aug 6. Apply12-0-12, 0.48 lb.N/1000 sq. ft., 50% slow release.
- Fifth application, Sept 3. Apply 6-0-12, 0.24 lb N/1000 sq. ft., 100% quick release.
- Sixth application, Sept 24. Apply 6-0-12, 0.24 lb.N/1000 sq. ft., 100% quick release.
Totals for season:
N – 2.16 lbs. /1000 sq. ft., 33% of which is slow release, 33% organic P – 0.0 lbs. P₂O₅ /1000 sq. ft.
K – 2.88 lbs. K₂O/1000 sq. ft.
Find this program on page 32 of “Best Management Practices for Landscape Fertilizer Use on Nantucket Island” by the Article 68 Work Group in 2010-2012, Nantucket, MA.
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