fertilizer dose

A soil test would be the optimum way to determine what type of fertilizer, if any, that you need. Also be aware that fertilizer applications may affect soil pH.  Soil tests are not exclusively used to determine nitrogen amounts due to the many climatic, chemical and biological factors that affect the amount of nitrogen in the soil at any given time.  Nitrogen results are thus based on research results from field experiments to determine the optimum application rate for turf or lawn grass.

The high nitrogen level in a fertilizer gives lawn grass fast shoot development and makes for a deeper green color. The phosphorus provides nutrition for good root development, and the potassium helps the roots build an immune system against diseases. The amounts of each ingredient will be different for various products, but the ratios needed by your lawn grass will remain basically the same over time. To use a fertilizer ratio calculations worksheet, please see this PDF document.

Make sure the lawn fertilizer you apply has complete nutrients in the bag and not just Nitrogen, Phosphate and Potash (N-P-K). Plants often need micronutrients such as iron, manganese, zinc and boron to meet essential growth requirements. A soil test can help make determine what elements need to be applied. Often iron is in critical shortage for alkaline soils and is a needed element for many warm season grasses. Seedland sells Pennington Lawn Fertilizer that includes other trace elements that may be needed for your lawn such as iron.

Many established lawns are fertilized with a weed & feed to control weeds and feed your lawn grass at the same time. Over time as your weed problem is reduced, you can usually switch to a fertilizer without the chemical control of a weed & feed. It is important that you read the directions on the container of weed and feed products and clearly determine that the product is suitable for your grass species. Never apply a weed and feed product to a new lawn, instead use a product such as Pennington Lawn & Grass Plug Starter sold online by Seedland.

New Lawn Starter Fertilizer

New lawn starter fertilizer should be your choice when planting seed or grass plugs in a new lawn. With an analysis of 18-24-6 you will get the phosphorous needed to establish a good root system and potassium to protect this new root system. The nitrogen contained in this fertilizer will assist with grass leaf or shoot development while ensuring a nice green color. This fertilizer also contains these additional elements -  Boron, Iron, Zinc, Copper, and Manganese.

Calculating Fertilizer Ratios*

If your soil test report recommends applying 1.5 lb of nitrogen, 0.5 lb of phosphate, and 0.5 lb of potash per 1000 sq ft, you should apply a fertilizer with a ratio of 3-1-1 since you need three times as much nitrogen as phosphate and three times as much nitrogen as potash. The simplest method of determining a ratio is to divide the weights of nitrogen, phosphate, and potash by the lowest weight of the three.

You can also determine fertilizer ratios from fertilizer numbers by dividing the percentage of nitrogen, phosphate, and potash by the lowest percentage of the three nutrients.

*Courtesy of Penn State AG Sciences Department

Yearly Fertilizer Rates For Grass Lawns

See the chart below to determine how much fertilizer to use on your particular lawn grass species per year. Please note that if you have planted a lawn grass mixture (multiple grass types) year long fertilization rates must be applied by establishing which grass species is the dominant grass and fertilize according to the needs of that grass.

Most all charts will give the rates in pounds of nitrogen per 1000 square feet for the growing season (year). We recommend a soil test to determine the additional, if any, nutrient needs of your lawn grass.

Lawn Grass Fertilization Rate Chart By Species

GRASS FERTILIZATION RATES: Lbs / 1000 sq. ft. of N per year.	LOW	HIGH
BAHIA GRASS - Pensacola & Argentine	2	5
BENT GRASS	3	6
BERMUDA - Hybrids & Common	2	5
BLUEGRASS	2	4
BUFFALO	1	2
CARPETGRASS	2	3
CENTIPEDE	1	3
FESCUE - Tall	2	3
FESCUE - Fine - Creeping - Chewings	1	2
RYE ANNUAL & PERENNIAL	2	3
ST. AUGUSTINE	3	6
ZOYSIA	2	4

Calculating Fertilizer Rates For Lawn Grass

From the chart above of "lbs. per 1000 sq. ft" of Nitrogen you can calculate the amount of fertilizer you actually need during a year. For example, if you have bluegrass under average maintenance you would need 3 lbs. of N yearly according to the above chart.

Calculate Actual Fertilizer Application For 1 Complete Year
Total Fertilizer For Multiple Applications

The first number in a fertilizer analysis is the nitrogen percentage. A bag of 25-4-6 fertilizer has 25% Nitrogen per bag. Divide this N amount into the lbs. per 1000 rate from the chart above. In this case divide 3 by .25 = 12 (use decimal conversion on the percentage i.e.: 25% = .25 )

This means that 1000 sq. ft. of your lawn would require 12 lbs. of this analysis of fertilizer in a YEARS time. This rate would provide a mid-range of maintenance (average) on a Bluegrass lawn. Thus under a mid-range maintenance plan, you would fertilize twice a year. Therefore you need to apply 6 lbs. of actual fertilizer per application twice a year per 1000 sq. ft. of your lawn --- A 18 lb. bag of lawn fertilizer, such as the one we sell, covers 5000 sq. ft.

Calculate Amount Of Fertilizer
Per Application - For Each 1,000 Sq. Ft.

Divide your fertilizer nitrogen analysis ( the first number) into 100. If the analysis is 27% Nitrogen. 100 divided by 27 = 3.71. That means you would need to apply 3.71 lbs. per 1000 sq. ft. to apply an actual rate of 1 LB of Nitrogen per application.

High Input Grasses

Grasses being highly maintained such as for golf courses and athletic fields will need more fertilization according to the intensive upkeep that is required to promote the fastest and thickest growth possible. Hybrid varieties such as these are the most care intensive of the grasses used for turf purposes. Fertilization programs based on weekly, bi-weekly or monthly applications are often required to maintain the grasses at optimum growth.

Make sure the lawn fertilizer you apply has complete nutrients in the bag and not just Nitrogen, Phosphate and Potash (N-P-K). Plants often need micronutrients such as iron, manganese, zinc and boron to meet essential growth requirements. A soil test can help make determine what elements need to be applied. Often iron is in critical shortage for alkaline soils and is a needed element for many warm season grasses.

Applying or Spreading Fertilizer

The best way and easiest way to distribute fertilizer is with a hand held spreader for small areas and a lawn drop spreader for larger areas. This evenly distributes the coverage needed. Avoid applying fertilizers by hand.

Many larger lawns are fertilized with a push broadcast spreader such as the one pictured at right. You should calibrate your spreader using the manufactures instructions included in new spreaders