Turfgrass fertilization is one of the most important cultural practices needed to maintain a healthy, dense stand of turf and the practice is especially important given the amount of traffic and intensity of use of many sports fields.  However, as with any practice, there are limits to how much fertilization is required and excessive fertilizer applications can be detrimental to the turf, to the environment, and to your budget.  The basic principles of fertilization are introduced here, and below you will find a wide range of publications, presentations, and podcasts regarding principles in sports field fertilization programming developed by STMA.

Regular Soil Testing is Critical
Each nutrient required for plant growth and development is critical to establish and maintain a healthy turfgrass.  Generally speaking, we divide the nutrients into two categories in terms of their use requirements: macronutrients (those required in relatively large amounts, listed in Figure 1) and micronutrients (those required in relatively small amounts, listed in Figure 2).  While sports turf managers focus mostly on nitrogen (N), phosphorus (P), and potassium (K) in developing a fertility program, each of these nutrients plays a critical role in the performance of your playing surface and if deficient (or excessive) in availability to the plant, can result in a failed turf.  Given its importance as a nutrient and its variability in chemical form etc. that can be found in a soil from one day to the next, N programs without soil testing are developed on the basis of the grass, its use, and the season.  However, the only way to really know how much of other nutrients should be applied almost always comes down to taking a soil test.  The test results ensure that the nutrient is applied in levels to maintain the health of the plants and to also eliminate excessive or unnecessary applications of nutrients. Soil tests will also give you a pH measurement and unless pH’s are appropriate, nutrient levels in the soil are a moot point for the plant. Soil tests should be conducted on a routine basis - every one (for sand-based fields) to three (for native soil fields) years is recommended.

For soil testing services, contact your local Cooperative Extension office/university soil testing lab or consult with your fertilizer suppliers/product vendors regarding licensed private labs that they can recommend.

Fertilizer Programs

Cool Season Turfgrass 

growth cool season 

With active growth occurring in the spring and fall, the best time to fertilize cool season turfgrasses with nitrogen (N) is from March to June and September to December, with the specific dates obviously varying based on geographic location. A good rule of thumb regarding timing fertilizer applications is ‘if it needs mowing, then it is growing’; when grass is actively growing is the ideal time to optimize the turfgrass response to a fertilizer application, particularly of a nitrogen source.  How much do you apply?  The soil test results will tell you how much fertilizer to apply for nutrients other than N, and while many soil test reports will not contain soil N levels, they will provide a recommendation for how much N to apply and when to treat.  As a rule of thumb, most state extension recommendations recommend readily available N (water soluble) should be in the range of 0.7 to 1 lb N per 1000 sq ft per active growing month.  

March - May: One to two applications may be necessary in the spring. This application assists with greening up the turf, but can be detrimental if there is a late frost.  

June - August: Heavy fertilizer applications in the middle of summer should be avoided due to heat and drought stressing the plants. If fertilization is necessary to promote turf recovery on heavily trafficked fields, spoon feeding (periodic applications up to 0.25 lb N per 1000 sq ft) during the summer months will maintain turfgrass health.

September: The best time to fertilize is in the late summer/early fall. As temperatures cool and day lengths shorten, cool season grasses not only initiate a lot of new shoot growth, but also produce more roots, rhizomes and stolons, and stored food (carbohydrates).  Fertilization promotes recovery from drought and heat related injury sustained during the summer months. Appropriate fall fertilization is likely more important for the spring performance of a cool-season field than spring fertilization!

October - December: Fertilization in the late fall is advantageous because the majority of nutrients are used for root growth. There is not much vertical growth. Late fall fertilization can also be beneficial to early spring green up.  One thing to consider that is very important from an environmental perspective:  do NOT apply fertilizer to frozen soils.  These nutrients will likely end up in a nearby water source by way of surface movement across the frozen soils.

Warm Season Turfgrass 

growth warm season 

With active growth occurring throughout the summer, the best time to fertilize warm season turfgrasses is from May to September.

April - May: Early spring fertilization will assist with spring green up, but refrain from significant N applications until the threat of frost/freeze has passed.  Too much spring N can promote shoot growth over roots and amplify the drain on the stored food in the stems that the plant is using to initiate the spring growth.   One of the best times to fertilize is late spring because plants are actively growing and storing and manufacturing carbohydrates.

June - August: Fertilization can continue throughout the summer.

September through mid-Fall: Again, the specific timing is site dependent, but N applications on heavily trafficked fields have been shown to enhance turf recovery and increase stored food reserves until a killing frost occurs.  An ideal way to fertilize in the fall is to apply lighter, more frequent N levels.

October - March: If a field has not been overseeded (see below), fertilization should not take place.

Overseeded Warm-season Fields
Overseeding warm-season fields with a cool-season grass means that one must balance what is best for both the warm-season and cool-season grasses.  Apply the principles previously discussed for the grasses, but give special attention to fertilization and the anticipated turf responses during the ‘transition’ periods (i.e. going from bermudagrass to overseeded ryegrass in the fall transition, and returning from ryegrass to bermudagrass in the spring transition).

Tips to Get the Most Out of Your Fertilizer
1. Soil test to determine the nutrient and lime needs of the plants.
2. Depending on the turfgrass species, apply nitrogen in the amounts needed to maintain a healthy, actively growing turf that has optimum traffic tolerance.
3. Apply nitrogen in multiple applications throughout the growing season.
4. Return clippings while mowing.
5. To avoid leaching, do not overwater or apply fertilizer to frozen soils.
6. Consider using a slow release (water insoluble) fertilizer and apply less frequently.
7. If using a quick release nitrogen source, water it in to avoid foliar burn (desiccation) of the leaves.

Additional Fertilizer Resources:

STMA Technical Bulletins:
Utilizing Soil Tests in Nutrient Management for Sports Fields 
Backpack and Hand-held Sprayer Calibration 
Boom Sprayer Calibration
Drop Spreader Calibration 
Rotary Spreader Calibration  
Plant and Environmental Responses to the Essential Nutrients
Quick Release Nitrogen
Slow Release Nitrogen
Compost Applications to Sports Fields
Athletic Field Management in the Spring 
Preparing a Field for Winter

University Resources:

Soil Testing for Turf Areas - University of Nebraska
Simplifying Soil Test Interpretations for Turf Professionals - University of Nebraska
A Guide to Turfgrass Nutrient Recommendations - Kansas State University
The Importance of pH - Virginia Tech

Fate and Transport of Phosphorus in Turfgrass Ecosystems - University of Nebraska
Basic Turfgrass Requirements - University of Tennessee
Essential Elements - University of Tennessee

What's the ideal fertilizer ratio for turfgrass? - University of Nebraska
Developing a Turf Fertilization Plan - University of Tennessee
Fertilizers - University of Tennessee
Building Your Fertility Program - Cornell University
Calculations Used to Determine the Amount of Fertilizer Needed to Treat Turf - Penn State University
How much phosphorus and potassium are really in your fertilizer? -
Penn State University
How to calculate a fertilizer ratio - Penn State University
Turfgrass Fertilization: A Basic Guide for Professional Turfgrass Managers  - Penn State University
Late Fall Fertilization of Athletic Fields  - Penn State University
Turfgrass Fertilization - Texas A&M University

Calibrating Sprayers and Spreaders for Athletic Fields and Golf Courses - University of Missouri
Calibrating Your Fertilizer Spreader - Penn State University

Liming - University of Tennessee
Liming Turfgrass Areas  - Penn State University
Using Composts to Improve Turf Performance  -
Penn State University
Using Spend Mushroom Substrate (Mushroom Soil) As A Soil Amendment to Improve Turf  - Penn State University

Fertilizer Sessions Featured at STMA Conferences:
2015 - The Nuts and Bolts of Applied Nutrient Management - Bryan G. Hopkins, Ph.D., James Gish, CSFM, and Jessica Buss
2013 - STMA 121 - Back to Basics: Getting the Most from Your Granular Fertilizers Speakers: Brad Jakubowski, Tom Samples, Ph.D.
2013 - STMA 206 - Fertility Management for Sand-based Systems Speaker: Nick Christians, Ph.D.
2012 - Perceived and Real Environmental Impacts of Phosphorus (also available as a recorded session here)
Speakers: Dr. Gwen Stahnke, Washington State University - Puyallup, Dr. Elizabeth Guertal, Auburn University
2012 - Environmental and Economic Considerations of Nitrogen Fertilization
Speaker: Dr. Elizabeth Guertal, Auburn University
2012 - Deciphering Your Soil Test (also available as a recorded session here)
Speaker: Dr. Elizabeth Guertal, Auburn University
2012 - Comparison of Synthetic and Organic Fertilizers for Sports Fields (available as a recorded session here)
Speaker: Dr. Tony Koski, Colorado State University

Fertility Podcasts
Turfgrass Fertility - Ohio State University
Foliar Fertilization Concepts - Ohio State University
Efficiency of Foliar Fertilization - Ohio State University
Potassium: Importance, Use, and Fate - Ohio State University
Phosphorus: Importance, Use, and Environmental Fate - Ohio State University
Effects of Nitrogen on Wear Tolerance of Athletic Fields - Ohio State University

International Resources