Nutrient Management

Proper nutrient management plays a key role in the reduction of environmental risk and increases course profitability. Among other benefits, applied nutrients inflate the available pool of nutrients and allow turfgrass to recover from damage, increase its resistance to stress, and increase its playability. However, the increase in available nutrients also increases the potential risk of environmental impact. Nutrients may move beyond the turfgrass via leaching or runoff, which may directly impact our environment. Other organisms also respond to increases in nutrients and, in some cases, these organisms may deleteriously alter our ecosystem. The goal of a proper nutrient management plan should be to apply the minimum necessary nutrients to achieve an acceptable playing surface and apply these nutrients in a manner that maximizes their plant uptake.

Regulatory Considerations

Principles

• Local and state regulations are in place to better manage nutrient risks based on the unique conditions that exist in your location. Designing a nutrient management plan within these regulations addresses local concerns and minimizes risk within your unique ecosystem.
• Depending on your location, regulatory agencies may include federal, state, or local policies.
• In general, if your location is regulated by nutrient policies (such as nutrient management plans), all of your nutrient BMP will be designed according to these policies.
• Understand the importance of nutrient licensing.

Best Management Practices

• Identify who must be licensed.
• Describe differing licenses, if applicable.
• Provide the minimum requirement.
• Detail the Continued Education Unit required to maintain the license.
• Understand the value of training programs.
• Contact local and state organizations for regulatory restrictions.

Soil Testing

Principles

• Soil testing may or may not provide the appropriate answers to your nutrient management questions. Consult with your local land-grant university to get the most current information and to better understand which soil test values are relevant in your location.
• Through proper sampling, laboratory analysis, interpretation of results, recommendations, and record keeping, soil testing can be used to manage nutrients more efficiently.

Best Management Practices

• Accurate and consistent sampling is essential to providing useful soil test information over time.
• Divide the course into logical components such as greens, fairways, tees, roughs, etc., for each hole.
• Ten to 15 soil samples should be randomly taken from each section and blended together to provide a representative, uniform soil sample.
• Each soil sample should be taken from the same depth.
• Use an extractant appropriate for your soils.
• The same extractant must be used for each test in order to compare soil test results over time.
• The purpose of a soil test is to provide the grower with a prediction of a plant’s response to an applied nutrient.
• If the location has correlation data between a given nutrient applied to soil and a response to that nutrient by turfgrass, then recommendations may provide expected results.
• If your location does not have correlation data, then soil test recommendations may be of little value.
• Keeping soil tests from prior years will allow you to observe changes over time.
• This practice can provide good evidence of the impact of your nutrient management plan.

Plant Tissue Analysis

Principles

• Because of the mobility and conversion of elements within the soil; soil sampling can be less predictable than tissue testing. Tissue testing provides a precise measurement of nutrients within the plant. Tissue test sufficiency ranges are only as good as the correlation data of a given element to an acceptable quality level of a given turfgrass. Typically, tissue correlation data are more prevalent than soil test correlation data and, therefore, programs designed around tissue testing may provide more reliable results.
• Through proper sampling, consistent intervals, and record keeping, tissue sampling may be used to measure existing turf health.

Best Management Practices

• Tissue samples may be collected during regular mowing.
• Do not collect tissue after any event that may alter the nutrient analysis. Events may include fertilization, topdressing, pesticide applications, etc.
• Place tissue in paper bags, not plastic.
• If possible, allow tissue samples to air-dry at your facility before mailing them.
• Poor-quality turfgrass that is of concern should be sampled separately from higher-quality turfgrass.
• When turfgrass begins to show signs of nutrient stress, a sample should be collected immediately.
• More frequent tissue sampling allows a more accurate assessment of your turfgrass nutrient status changes over time.
• The quantity of tissue analysis you choose to use is entirely up to you and your needs. However, two to four tests per year are common on greens and one to two tests per year are common on tees and fairways.
• Keeping tissue tests from prior years will allow you to observe changes over time.
• Tissue testing can provide good evidence of the impact of your nutrient management plan.

Fertilizers Used in Golf Course Management

Principles

Understanding the components of fertilizers, the fertilizer label, and the function of each element within the plant are all essential in the development of an efficient nutrient management program.

Terminology

• Grade or analysis is the percent by weight of Nitrogen (N), Phosphorous fertilizer (P₂O₅) and Potassium fertilizer (K₂O) that is guaranteed to be in the fertilizer.
• A complete fertilizer contains N, P₂O₅, and K₂O.
• The laws governing the labeling of fertilizer vary greatly among states. Consult your land-grant university or the appropriate state agency regarding the laws in your location.

Label

• The label is intended to inform the user about the contents of the fertilizer which, if understood and followed, will result in little to no environmental risk.
• The fertilizer label may contain:
  • Brand
  • Grade
  • Manufacturer’s name and address
  • Guaranteed analysis
  • “Derived from” statement
  • Net weight

Macronutrients

Macronutrients are required in the greatest quantities and include nitrogen (N), phosphorus (P), and potassium (K).

Understanding the role of each macronutrient within the plant should provide you with a greater understanding of why these nutrients play such a key role in proper turfgrass management.

The role of nitrogen (N)

Nitrogen is required by the plant in greater quantities than any other element except carbon (C), hydrogen (H), and oxygen (O). Nitrogen plays a role in numerous plant functions including an essential component of amino acids, proteins and nucleic acids.

• Fate and transformation of N
• The goal of all applied nutrients is to maximize plant uptake while minimizing nutrient losses. Understanding each process will increase your ability to make sound management decisions and ultimately leads to an increase in course profitability and a reduction in environmental risk.
• Nitrogen processes
  • Mineralization: the microbial mediated conversion of organic N into plant-available NH₄
  • Nitrification: the microbial-mediated conversion of NH₄ to NO₃
  • Denitrification: the microbial mediated conversion of NO₃ to N gas; this primarily occurs in low-oxygen environments and is enhanced by high soil pH
  • Volatilization: the conversion of NH₄ to NH₃ gas
  • Leaching: the downward movement of an element below the rootzone
  • Runoff: the lateral movement of an element beyond the intended turfgrass location
• The release mechanism and factors influencing N release from available N sources

Understanding how certain N sources should be blended and applied is an essential component in an efficient nutrient management plan. In many cases, N sources are applied without regard to their release characteristics. This is an improper practice and increases the risk of negative environmental impact. Each N source (particularly slow-release forms) is unique and therefore should be managed accordingly. Applying a polymer-coated urea in the same manner one would apply a sulfur-coated urea greatly reduces the value of the polymer-coated urea. Similarly, applying 2 pounds of N from ammonium sulfate may cause burning, while applying 2 pounds of N from certain polymer-coated ureas may not provide the desired turfgrass response. Rate, application date, location, and turfgrass species all should be included in your nutrient application decision.

• Soluble nitrogen sources
  • Urea (46-0-0)
  • Ammonium nitrate (34-0-0)
  • Ammonium sulfate (21-0-0)
  • Diammonium phosphate (18-46-0)
  • Monoammonium phosphate (11-52-0)
  • Calcium nitrate (15.5-0-0)
  • Potassium nitrate (13-0-44) 
• Slow-release nitrogen sources

A slow-release N source is any N-containing fertilizer where the release of N into the soil is delayed either by requiring microbial degradation of the N source, by coating the N substrate which delays the dissolution of N, or by reducing the water solubility of the N source.

These include:

• Sulfur-coated urea
• Polymer/resin-coated
• Isobutylidene diurea
• Urea-formaldehyde/ureaformaldehyde reaction products
• Natural organic

• Urease and nitrification inhibitors
  • Urease inhibitors reduce the activity of the urease enzyme resulting in a reduction of volatilization and an increase in plant-available N.
  • Nitrification inhibitors reduce the activity of Nitrosomonas bacteria, which are responsible for the conversion of NH₄ to NO₂. This reduced activity results in a reduction of N lost via denitrification and an increase in plant-available N.

The role of phosphorous (P)

Phosphorus can be a growth-limiting factor for many unintended organisms and is a major contributor to eutrophication of water bodies. Thus, proper timing and rates should be implemented to reduce the risk of off-site movement of phosphorus.

Phosphorus forms high-energy compounds that are used to transfer energy within the plant. Phosphorus may remain in an inorganic form or may become  incorporated into organic compounds. Phosphorous application rates should be based upon soil test results derived from documented correlations demonstrating a turf response to soil test phosphorous levels.

• P deficiency symptoms
  • Initially, reduced shoot growth and dark green color may be observed
  • Later, lower leaves may turn reddish at the tips and then the color may progress down the blade
• P sufficiency ranges

Consult your land-grant university for sufficiency ranges in your location.

• P fertilizer sources
  • Diammonium phosphate
  • Concentrated superphosphate
  • Monoammonium phosphate
  • Natural organics

The role of potassium (K)

Potassium is of no environmental concern, but can be an economic concern, particularly when potassium is over-utilized, which can be quite common. Generally, potassium concentrations in turfgrass tissue are about 1/3 to ½ that of nitrogen.

Potassium is not a component of any organic compound and moves readily within the plant. Potassium is key component of osmoregulation which has been documented to increase stress resistance.

• K deficiency symptoms

Except under severe, documented deficiencies, K may not have an observable influence on turfgrass quality. Yellowing of older leaves followed by tip dieback and scorching of leaf margins have been reported. 

• K sufficiency ranges

Consult your land-grant university for sufficiency ranges in your location. 

• K fertilizer sources
  • Potassium sulfate
  • Potassium chloride
  • Potassium nitrate

Secondary Macronutrients

Secondary macronutrients are essential to plant function and are required in quantities less than N, P, and K, but more than micronutrients.  These include calcium (Ca), magnesium (Mg), and sulfur (S)

The role of calcium (Ca)

• Primarily a component of cell walls and structure
• Consult your land-grant university for sufficiency ranges in your location
• Found in gypsum, limestone, and calcium chloride

The role of magnesium (Mg)

• Central ion in the chlorophyll molecule and chlorophyll synthesis
• Consult your land-grant university for sufficiency ranges in your location
• Found in S-Po-Mg, dolomitic limestone, and magnesium sulfate

The role of sulfur (S)

• Metabolized into the amino acid, cysteine, which is used in various proteins and enzymes
• Consult your land-grant university for sufficiency ranges in your location
• Found in ammonium sulfate, elemental sulfur, gypsum, potassium sulfate

Micronutrients

Understanding the role of each micronutrient within the plant should provide you with a greater understanding of why these nutrients play such a key role in proper turfgrass management.

Micronutrients are just as essential for proper turfgrass health as macronutrients, but they are required in very small quantities compared to macronutrients. Micronutrients include iron (Fe), manganese (Mn), boron (B), copper (Cu), zinc (Zn), molybdenum (Mo), and Chlorine (Cl).

Consult your land-grant university for micronutrient sufficiency ranges in your location.

The role of iron (Fe)

• Is part of the catalytic enzymes and is required for chlorophyll synthesis
•  Affects photosynthesis, nitrogen fixation, and respiration
• Consult your land-grant university for sufficiency ranges in your location

The role of manganese (Mn)

• Involved in photosynthesis
• Required as a cofactor for ~35 enzymes
• Lignin biosynthesis depends on Mn

The role of boron (B)

• Found in the cell wall; probably required for the structural integrity of the cell wall

The role of copper (Cu)

• Cu-protein plastocyanin is involved in photosynthesis
• Cofactor for a variety of oxidative enzymes

The role of zinc (Zn)

• Structural component of enzymes
• Protein synthesis requires Zn
• Carbohydrate metabolism affected by Zn

The role of molybdenum (Mo)

• Primarily related to nitrogen metabolism
• Structural and catalytical functions of enzymes

The role of chlorine (Cl)

• Required for the oxygen-evolving reactions of photosynthesis
•  Also appears to be required for cell division in both leaves and shoots

Soil pH

Principle

Identifying pH levels may be the most important soil test result for turfgrass managers. In most cases, a pH of 6.3 is ideal because it provides the greatest probability of micronutrient availability. Soil pH adjustments may occur slowly and are temporary.

Best Management Practices

• To increase soil pH, apply a liming material (calcium carbonate, calcium oxide, dolomitic limestone) that contains Ca²⁺ and neutralizes acidity.
• To lower soil pH, products containing elemental sulfur should be applied.
• In some cases, utilizing injection pumps into irrigation water to address pH can be beneficial.

Nutrient Management

Principles

• Within each state, environmental conditions vary greatly including differences among soils, topography, rainfall, and temperature. These differences require that a nutrient management plan be flexible enough to allow turfgrass managers to address their unique needs.
• Understand the importance of application timing for effective use of applied nutrients.

Best Management Practices

• The objective of all nutrient applications is plant uptake and the corresponding desirable response.
• Apply nutrients when turfgrass is actively growing.
• Apply slow-release N fertilizers at the appropriate time of year to maximize the products’ release characteristics. For example, an application of slow-release N to warm-season turfgrasses in fall may not be as effective as the same application applied in early summer because of the prolonged release time in fall.
• Follow N application rate recommendations from your local land-grant university.
• N application rates from slow-release materials should take into consideration the release rate of the chosen material. If insufficient material is applied, the desired response may not be observed.
• Consult your local land-grant university for efficient N:K in your location.
• The reduced height of cut and excessive traffic damage on putting greens results in an increased need for growth leading to an increase in nutrition.
• Tees and landing areas often have higher fertility requirements than fairways and roughs because they suffer constant divot damage.
• Fairways and roughs often require less nutrient inputs than other locations because of their increased height of cut, less damage, and clipping return.
• Exercise caution when applying nutrient applications during turfgrass establishment as these applications are particularly susceptible to loss via leaching and runoff.
• Provide appropriate rates and products to minimize N loss without reducing turfgrass establishment.
  • Increased water applications
  • Increased nutrients to hasten establishment
  • Reduced root mass
• Be aware of the different types of spreaders and understand the advantages and disadvantages of each.
• Not all fertilizers can be spread with every spreader. For example, if sulfur-coated urea was spread through a drop spreader, the sulfur coating could be damaged, essentially leading to an application of soluble urea.
• Choose the appropriate spreader for a given fertilizer material.
  • Walk-behind rotary
  • Drop spreader
  • Bulk rotary
  • Spray
  • Calibration reduces environmental risk and increases profitability.
• Proper fertilizer storage, loading, and clean-up reduce environmental risk.
• Avoid applying fertilizer to soils that are at, or near, field capacity or following rain events that leave the soils wet.
• Do not apply fertilizer when the National Weather Service has issued a flood, tropical storm, or hurricane water or warning, or if heavy rains are likely.