5 Nutrient Management
Proper nutrient management plays a key role in the reduction of environmental risk and also increases course profitability. Among other benefits, applied nutrients increase the available pool of nutrients and allow turfgrass to recover from damage, improve its resistance to stress, and increase its playability. However, an increase in available nutrients also raises the potential risk of environmental impact. Nutrients may move beyond the turfgrass via leaching or runoff, which may directly impact water quality. Other organisms also respond to increases in nutrients and, in some cases, these organisms may deleteriously alter the 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.
5.1 Regulatory Considerations
Virginia regulations (4 VAC 5-15) serve as the basis for developing certified Nutrient Management Plans (NMPs) to limit nutrient (primarily N and P) and sediment pollutants from reaching water and entering watersheds. DCR certifies individuals to write NMPs for turf and landscape. These regulations provide the basis for developing environmentally responsible NMPs that consider both warm-season and cool-season grasses, the turf use, soil type, and nutrient application levels and frequencies for both grow-in and general management purposes. A certified nutrient management planner uses these recommendations in developing a site-specific nutrient management plan. For more information, see the Urban Nutrient Management page on the DCR website.
5.2 Soil Testing
Soil testing provides the basis for sound nutrient management and water quality protection programs in golf turf management, especially given the dynamic nature of the sandy soils of many putting greens and tees. A standard soil test provides information on soil pH and the levels of the macronutrients P, potassium (K), calcium (Ca), and magnesium (Mg) and typical micronutrients iron (Fe), zinc (Zn), copper (Cu), and boron (B). Soil test results do not provide N levels because N constantly fluctuates between plant available and unavailable forms. However, soil test results typically provide a recommendation for N levels and timing of applications.
General soil test sampling and analytical testing recommendations include the following:
- Conduct soil sampling at a 4-6” depth from representative areas of similar management.
- Exclusively use one trusted soil testing laboratory.
- Verify whether the lab uses Mehlich-3 or Mehlich-1 extractions and use appropriate conversion factors for developing and implementing a nutrient management plan.
One of the best ways to utilize soil testing is to monitor changes in the nutrients over time. Declining soil test P and K, for example, indicates that fertilization with P2O5 and K2O should be increased relative to N fertilization rate, unless the values for those nutrients are deemed to be high. Nitrogen fertilizer drives the uptake of all other nutrients in turf. Therefore, P2O5 and K2O should be looked at relative to N fertilization rate and not just the total amount applied.
For more detailed information on soil testing, see Chapter 5 of the Urban Nutrient Management Handbook, VCE.
5.3 Soil pH
Soil pH is an assessment of the total amount of hydrogen ions (H+) in soil solution (“active acidity”) and those ions attracted to soil colloids (“reserve acidity”). Nutrients may be present in the soil but not available to plants because nutrient availability to plants is governed primarily by pH. (graphic from 1st edition TBA) shows that slightly acidic soils are optimal for nutrient availability (typically a pH of 6.2 to 6.8 for golf turf management). Extremes in soil pH result in nutrient deficiency or toxicity, both of which can cause suboptimal growth conditions and ultimately lead to turf loss.
5.4 Plant Tissue Analysis
Visible plant symptoms can offer helpful clues in diagnosing nutrient deficiencies, but can also be easily confused and misinterpreted, especially where micronutrients or sulfur compounds are involved. Tissue testing can help to adjust nutrient management programs in these ways:
- To confirm a suspected nutrient element deficiency when visual symptoms are present
- To monitor plant nutrient element status in order to determine whether each tested nutrient is in sufficient concentration for optimum performance.
Recent soil test results should be used to assist in the interpretation of the results of a plant tissue analysis. If none are available, a soil sample should be submitted along with the tissue sample.
5.4.1 Nutrient Monitoring
Tissue tests can indicate ranges in possible nutrient excesses or deficiencies, but the data does not explain the cause of the nutrient deficiency (such as unsuitable pH, or deficiency or excess in nutrient application).
A routine monitoring program and the resulting recommendations provide a basis for effective nutrient management practices. Some golf course superintendents submit samples to testing labs every month or every other month, especially for creeping bentgrass grown on completely modified sand-based putting greens. Trends in tissue nutrient status can be observed, and in conjunction with soil test data, can be used to make adjustments in lime and fertilizer treatments before deficiencies or excesses develop. In addition, by comparing plant analysis results with turf quality, nutrient applications, and soil test data over time, the nutrient sufficiency ranges and nutrient management practices required to maintain site-specific turf quality under varying climatic conditions and management constraints can be refined. If regular sampling is cost prohibitive, then prioritized sampling is recommended and should include areas that are representative of the turf quality, use, composition, and soils.
5.4.2 Plant Sampling
Plant samples should be taken at regular intervals from each representative area prior to and during growth cycles. Turf quality (clipping yields if available), weather conditions, and any known problems at the time of sampling should be recorded. Nutrient additions on each monitored site should be documented and routine soil samples collected at least once a year (prior to P and K fertilization) to supplement nutrient management records.
For diagnostic samples, plant tissue samples should be collected as soon as symptoms appear. Plants showing severe deficiency symptoms are often the most difficult to interpret correctly, since a deficiency of one element may result in deficiencies or excess accumulation of other elements if uncorrected. Plants under prolonged stress of any kind (temperature or moisture extremes, pests, flooding, mechanical damage, etc.) can have unexpectedly high or low nutrient levels due to the stress.
Comparative sampling can improve the accuracy of diagnosis by collecting both plant and soil samples from “good” and “bad” areas that are close proximity to each other and have similar soil types, similar species composition, and similar management (mowing height, irrigation, etc.). Since the recommended ranges of plant nutrient content are general, a sample should represent general site and management conditions. Differences in nutrient concentrations can then be compared with soil samples to determine if the problem is related to fertility management or is an uptake problem (such as disease, water, compaction, or root damage). For example, differences in Mg and Mn between plants could be related to differences in soil pH.
Samples should be collected from the above-ground portion of the plant, clipped just above ground level no more than two days after mowing. As a general rule, monitoring samples can be taken from turfgrass clippings collected in buckets, as long as the bucket is clean and the clippings are not contaminated from chemical applications (fertilizers, pesticides, reel-sharpening compounds, etc.). When whole plants are sampled, the roots should be cut off and discarded and shoots washed to remove soil particles. Under normal conditions, rainfall is frequent enough to keep leaf surfaces fairly free from dust and soil particles. If recently sprayed, or if Fe is of primary interest, a quick wash in a dilute (0.3%) detergent solution followed by a quick rinse in a strainer or colander removes residues and soil particles that could bias the sample. To prevent decay during transport to the lab, excess moisture should be reduced by partially air drying plant tissue samples before shipment to the laboratory. Fresh samples should not be put in a tightly sealed or plastic bag unless they will be kept cold during transport.
5.5 Fertilizers Used in Golf Course Management
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. In Virginia, VDACS analyzes samples of fertilizer and agricultural lime sources to ensure that labeling guarantees are met and that the product is safe for the environment.
Grade or analysis is the percent by weight of N, P, and K that is guaranteed to be in the fertilizer at minimum. Complete fertilizers contain N, P, and K.
The label is intended to inform the user about the contents of the fertilizer. When applied according to the label, the use of fertilizer presents little to no environmental risk. Fertilizer labels generally provide the following information:
- Manufacturer’s name and address.
- Brand name.
- Nutrient guarantee (i.e. guaranteed minimum amounts of nutrients, given as a ratio).
Additional information that may be found on the label includes characteristics such as size guide number (SGN), water-insoluble nitrogen (WIN), WSN, and release characteristics.
Nitrogen sources get the most scrutiny in a management program because of the intensity of golf turf management and the highly variable grass requirements, based on the turfgrass species, turf use, maintenance requirements, and soil type. A wide variety of N sources are available, but only two forms of N are plant available: the ammonium cation (NH4+) and the nitrate anion (NO3-). Regardless of the source, N must be transformed into one of these two forms to become plant available. Given its positive charge, NH4+ can be temporarily bound in the soil by cation-exchange capacity (CEC) reactions. NO3- is highly prone to leaching and can quickly contribute to water quality issues, particularly for sand-based soils with very low CEC.
The first selection criterion in choosing an N fertilizer source is often its water solubility. Readily available N sources, such as WSN, provide rapid turfgrass growth and color responses and are more prone to leaching, particularly in sand-based soils often used for golf putting greens or tees. SAN sources, often referred to as WIN or controlled release N (CRN), are highly variable in N content and release characteristics.
The latest generation of “stabilized” N sources cannot be adequately described on the basis of N solubility. The Association of American Plant Food Control Officials (AAPFCO) adopted the term “enhanced efficiency” (EE) to better describe fertilizer products that minimize the potential of nutrient losses to the environment, as compared with a “reference soluble” product such as WSN or SAN. This term distinguishes between two categories of EE fertilizer products:
- “Slow release” fertilizer sources release or convert nutrients to a plant-available form at a slower rate relative to a “reference soluble” product. For these products, the release of soluble nutrients is governed by either a coating or occluded materials (such as polymer or sulfur-coating, urea form and derivatives, and isobutyraldehyde diurea).
- “Stabilized” N sources are amended with an additive that reduces the rate of transformation of fertilizer compounds, resulting in extended time of availability in the soil, such as nitrification inhibitors, nitrogen stabilizers, and urease inhibitors.
Both categories of products improve nutrient use efficiency and minimize the potential of nutrient losses to the environment. AAPFCO is refining the definition of these products and their labeling characteristics as technologies evolve.
Nitrogen solubility and stabilization are highly variable, depending on the source and possible combinations with readily available materials. While SAN and stabilized sources are significantly more expensive on a cost per pound of N basis as compared with WSN materials, their release characteristics fit well given the precision required in golf turf management and their use is encouraged whenever possible.
5.6.1 Nitrogen Application
As a rule of thumb, no more than 0.7 lb of readily available N per 1,000 ft2 per growing month or 0.9 lb of slowly available N per 1,000 ft2 per growing month for cool-season grasses should be applied in a single application. For warm-season grasses, no more than 1 lb of N per 1,000 ft2 per growing month should be applied in a single application. When possible, these should be split into two or more applications. This strategy meets turfgrass nutritional needs and regulatory requirements while minimizing potential water quality concerns. Restricting N application levels is especially important on sand-based putting greens and is easily adapted into green management programs, where it is commonplace for superintendents to “spoon-feed” (0.05 to 0.15 lb N/1,000 ft2) the turf, making numerous light applications of nutrients on a frequent basis. This strategy balances turfgrass growth and color with requirements for turf health, recovery, and playability, in addition to reducing nutrient leaching potential.
Spoon-feeding can be accomplished with both granular and liquid applications. The practice of liquid feeding or foliar feeding is popular for facilities with spraying equipment. Liquid feeding uses greater than 45 gallons per acre (gal/A) of water and most nutrient uptake occurs at the root system. Foliar feeding uses less than 45 gal/A water carrier in order to keep the majority of the nutrients on the leaf surface for foliar absorption.
Applying fertilizer in water improves the uniformity of distribution and allows small amounts of nutrients to be accurately applied with water as the carrier. Fertigation (delivery through an irrigation system) is another specialized means of delivering nutrients and is especially effective during a grow-in when wet soils are not conducive to spreader and/or sprayer operation. Fertigation performance is only as good as the distribution and uniformity capabilities of the irrigation system. Dispersible granule fertilizer formulations provide enhanced turf coverage that mimics foliar or liquid feeding. Upon contact with water, a single fertilizer granule separates into several thousand particles, thus coating the turfgrass foliage.
Phosphorus is a critical nutrient for turfgrass growth and development, playing important roles in energy transformations in plant cells and root development. P enhances turfgrass establishment and is the most important nutrient in “starter fertilizers.” In the soil, P is generally in complex with other elements and is an insoluble (plant unavailable) nutrient.
Phosphorus is slowly made available to plants on an as-needed basis by chemical reactions in the soil that convert it to either of two anionic forms: HPO42- or H2PO4-. In these anionic forms, phosphorus is highly leachable and is a concern for water quality issues since it contributes to eutrophication. However, the complexing of P with other elements greatly minimizes P leaching as compared with NO3- leaching potential. Phosphates are a potential leaching concern during the grow-in of turfgrass on sand-based systems that inherently have very low nutrient holding capacity and are subject to frequent irrigation when the turfgrass has a very limited root system. Leaching can also be a concern where P is overapplied to established turf, especially on sand-based systems. In native soils, P leaching is typically of minimal concern unless P has been overapplied for many seasons. P leaching potential is best managed by applying it on the basis of a soil test. Applying fertilizers near water resources and/or impervious surfaces that move stormwater contribute to water quality concerns and should be avoided.
The standard P fertilizer sources are provided in Table 6-3 in the 1st edition. Recent changes in fertilizer manufacturing include the production of “P-free” fertilizer sources. In addition, interest in natural organic fertilizers has grown, but these are not “P-free” and are typically 0.5 -2% P2O5 by weight. Phosphonate (phosphite) is a unique form of P used in the golf turf industry primarily for its activity on Pythium induced turf diseases (Landschoot and Cook, 2009). Numerous labeled phosphonate fungicides have been shown to be low cost, extremely effective Pythium control products when used on a preventive basis. Phosphonates are most often referred to in the golf turf industry as “plant health products” since they have such low nutrient value, but can be converted to plant available phosphate by soil-borne bacteria over time (three to 12 months). Hence, their use warrants some consideration by golf turf managers and nutrient management planners. The normal use rates for Pythium disease suppression are so low compared with standard phosphate-containing fertilizers that they would not be anticipated to contribute to excessive soil loading of P that might ultimately lead to phosphate leaching.
Potassium is not a direct component of any organic compound within a plant but is heavily involved in many biochemical responses. In particular, K is the nutrient that most impacts water relations within the plant, sometimes referred to as the “antifreeze” and “coolant” nutrient of the plant world. The most common forms of potassium fertilizer sources are presented in Table 6-4 in the 1st edition. Because the last of the three numbers that appear in the fertilizer grade represents potash (K2O), this value must be converted to elemental K by multiplying by 0.83.
Although many unrefined and manufactured sources of potassium exist, plants always absorb potassium in the same form, the K+ cation. K is required in the second highest quantities by plants after N. As a cation, K+ can be temporarily bound and exchanged for other cations (i.e. cation exchange) in soils that contain significant anionic (negatively charged) exchange sites (i.e. soils with significant amounts of clay and/or organic matter). Even as a cation, K+ can still leach depending on soil type (especially sand-based soils) and under heavy rainfall or irrigation. Potassium is not considered to be an environmental concern that negatively impacts water quality and therefore does not receive as much attention as N and P from this perspective.
5.9 Calcium, Magnesium, and Sulfur
While much time is spent on N, P, and K, when it comes to nutrient management programs for golf turf, Ca, Mg, and sulfur (S) are equally important for plant growth and development. In addition to the common sources listed in Table 7, other materials such as bone meal, wood ash, manures, and sludge can contain significant amounts of these elements.
Many of these sources also alter pH (i.e. liming materials that raise pH, sulfur-based materials that lower pH). Therefore, if Ca, Mg, or S is limiting in the soil, but a pH change is not desired, standard liming sources and elemental S should be avoided and gypsum (CaSO4), magnesium sulfate, or potassium-magnesium-sulfate used to supply these nutrients.
Table 7. Secondary macronutrients
|Calcium||Primarily a component of cells walls and structure.||Gypsum
|Magnesium||Central ion in the chlorophyll molecule and chlorophyll synthesis.||S-Po-Mg
|Sulfur||Metabolized into the amino acid cysteine, which is used in various proteins and enzymes.||Ammonium sulfate
Micronutrients are just as essential for proper turfgrass health as macronutrients but are required in very small quantities compared with macronutrients. Micronutrients include iron (Fe), manganese (Mn), boron (B), copper (Cu), zinc (Zn), molybdenum (Mo), and chlorine (Cl). They play a variety of roles in turf biology, including roles in photosynthesis, nitrogen fixation, and protein synthesis. Micronutrient deficiencies can be confirmed by tissue testing or small fertilizer applications to turf to verify fertilizer response. Soil testing for micronutrients is not recommended, and soil interpretations for these nutrients can be ignored.
Fe and Mn deficiency symptoms can be common in bluegrasses and bentgrass during summer. Deficiency symptoms include yellow colored (chlorotic) turf that does not respond to N fertilization. In many instances, nitrogen fertilization will intensify the chlorosis. The chlorosis is most severe when soils are warm, wet, and have high pH (>7.3). It is believed that root function is lost under these conditions. As a result, foliar Fe and Mn applications will effectively correct the deficiency. Deficiency symptoms subside as the soil cools into the fall.
5.11 Managing Soil pH
Most of the native soils of Virginia essentially act as weak acids, with only a small portion of their potential acidity present in the active, or soil solution form. Acidic soil (with a low pH) must be limed based on a soil test recommendation to make the rooting environment hospitable for root exploration and development. Golf turf soils are rarely too alkaline (with a high pH) in this region. High alkalinity is typically due to excessive lime applications made without soil test recommendations. High alkalinity should be avoided due to the difficulty of managing high pH soils as compared with low pH soils.
Selection of liming materials is typically based on the ability to neutralize soil acidity, chemical composition, fineness of grind, ease of handling, and cost (Little and Watson, 2002). Whenever possible, soil pH should be adjusted prior to establishment as preplant incorporation greatly accelerates the neutralization of the acidity throughout the root zone. For more information on liming materials and rates, see Chapter 6 in the 1st edition of Environmental Best Management Practices for Virginia’s Golf Courses.
5.12 Nutrient Application Programs and Strategies
Defining an ideal nutrient application strategy given all of the variables (grass, grass use, soil, climate, budget, equipment available, etc.) is impossible for golf turf management fertility programs. However, four general management principles apply:
- Apply the right rate of fertilizer.
- Apply fertilizer at the right time.
- Apply fertilizer in the right place.
- Use the most appropriate type of fertilizer.
The required Nutrient Management Plan provides the basis for developing a nutrient management strategy that optimizes plant health in an environmentally responsible manner.
To improve application efficiency, a spatial assessment of nutrient requirements that calibrate nutrient applications to plant growth can be performed. Using Minimal Levels for Sustainable Nutrition Soil Guidelines soil nutrient interpretation guidelines and the turfgrass growth potential (GP) model, nutrient needs can be predicted based on variable plant demand through the growing season. This approach ensures nutrients are applied in amounts and at times when plants are most capable of uptake and utilization and can effectively reduce costs in nutritional programs through reduced applications. For more information on Minimum Level for Sustainable Nutrition (MLSN) guidelines, see also the MLSN Cheat Sheet.
5.12.1 Fertilizer Application Timing
The timing of fertilizer applications (N in particular) is one of the most critical aspects for protecting water quality. The vast array of slowly available N sources, many of which are extremely immobile in soils, provides some flexibility in N application timing.
N should be applied during periods of optimal turfgrass growth. For cool-season grasses, typical management programs result in two-thirds to three-fourths of a seasonal N application applied in the fall, with the remaining one-fourth to one-third applied in early to mid-spring. For warm-season grasses, the N application period typically extends from mid-spring through late summer.
The DCR Nutrient Management Standards and Criteria recommends the application for N fertilizers to cool-season turfgrass beginning six weeks prior to the last spring average killing frost date and ending six weeks after the first fall average killing frost date. For non-overseeded warm-season turfgrasses, N applications should begin no earlier than the last spring average killing frost date and end no later than one month prior to the first fall average killing frost date. Utilizing lower N application levels during the early and late periods of the application window further promotes nutrient use efficiency and less potential for water quality impacts. Combining these timing recommendations with sound agronomic decision making minimizes the likelihood of potentially mobile (both surface and subsurface) nutrients entering water sources during non-active growing periods.
5.12.2 Maintenance Fertilization
Given the diversity in grasses and their intended uses on Virginia golf courses, maintenance fertility programs are also highly diverse in terms of fertility source, application rate, and frequency. Highly leachable sand-based soils and regular clipping removal, two characteristics associated with the putting green and tee management, further increase the intensity of nutrient management under these conditions.
Table 8 presents general seasonal N applications for all aspects of golf turf management developed from VA regulations. Maximum N levels are not intended to be interpreted as “optimal” N levels for single applications. Every putting green, tee, etc. has its own site-specific nutritional requirements, and it is highly likely (and probably desirable from a plant health and environmental perspective) that the applications are split into frequent, light applications of nutrients, especially for putting green management. As with establishment fertilization, fertilization applications should be timed during periods of active turfgrass growth and the percentages of readily- and slowly-available N in products should be used to determine application rates, with typically no more than 0.7 lb of N per 1,000 ft2 applied per growing month.
Table 8. General seasonal N strategies for golf turf management
|Turf Use||Grass Type||Maximum N Rate Per Application – WSN||Total Annual N Rate – SAN|
|Greens||0.7 (b)||3 – 6|
|Tees||0.7 (b)||2 – 5|
|2 – 3
3 – 4
|3 – 4
3.5 – 4.5
|Roughs||0.7 (e)||1 – 3|
|(b) Greens and Tees – Per application timing must be a minimum of 30 days between applications. A rate of 0.9 lbs/1,000 ft2 of total N may be applied for cool season grasses or 1.0 lbs/1,000 ft2 of total N may be applied for warm season grasses using a material containing slowly available forms of N.
(c) Fairways (normal management; non-irrigated or irrigated) – Per application timing must be a minimum of 30 days between applications. Total N application rates of 0.9 lbs/1,000 ft2 of total N may be applied for cool seasons grasses or 1.0 lbs/1,000 ft2 of total N may be applied for warm season grasses using a material containing slowly available forms of N.
(d) Fairways (intensive management; irrigated) – Per application timing must be a minimum of 15 days between applications. This option requires optimized timing of more frequent applications of N with lesser rates per application. Alternatively, a maximum application rate of 0.9 lbs/1,000 ft2 of total N for cool season grasses or 1.0 lbs/1,000 ft2 of total N for warm season grasses using a material containing slowly available forms of N may be applied with a minimum of 30 days between applications.
(e) Foliar fertilizer may be applied to warm season grasses within 30 days prior to the first killing frost in the fall, at a rate not to exceed 0.1 lbs/1,000 ft2 of N per application. This application must be accounted for tin the total annual N rate.
5.12.3 Site-Specific Considerations
Additional considerations for fertilization management depend on weather forecasts and site-specific characteristics within each area of a golf course. For example, the following are recommendations for topographic, geologic, soils, climate, and cultural considerations that should be accounted prior to fertilization applications. Following these recommendations minimizes the amount of nutrients in runoff and/or groundwater:
- Minimize fertilizer application rates on slopes.
- Use N levels of 0.25-0.5 lb per 1,000 ft2 per application on deep sandy soils or near shallow water tables.
- Avoid applying fertilizers prior to anticipated intensive, heavy rainfall.
- Ensure all fertilizers are applied or are moved into turfed areas so that they do not remain on impervious surfaces where they can move in stormwater.
- Establish minimal maintenance buffer zones around stream and lake boundaries.
5.13 Application Equipment
The selection and calibration of application equipment is another important aspect of nutrient management. Not all fertilizers can be spread with every spreader. For example, if sulfur-coated urea is spread through a drop spreader, the sulfur coating could be damaged, essentially leading to an application of soluble urea. Therefore, choosing the appropriate spreader for a given material (walk-behind rotary drop spreader, bulk rotary, or spray) is important.
Accurately calibrated sprayers or spreaders are essential for proper application of fertilizers. Incorrectly calibrated equipment can easily apply too little or too much fertilizer, resulting in damaged turf, excess cost, and greater potential of nutrient movement off-site. An excellent resource for spreader care and calibration can be found at Penn State’s Department of Plant Science website. Spreaders should also be thoroughly cleaned after use due to the high salt content that corrodes metal parts and in keeping with the BMPs for equipment washing.
5.14 Nutrient Management Best Management Practices
- Because turf is extremely responsive to soil N status, evaluate changes in clipping yield during the growing season to estimate N availability.
- Reduce N inputs on more mature turfgrass stands.
- Adapt N fertilizer programs to provide turfgrasses with an even growth rate. This increases golf course playability and minimizes the risk to the environment, while excessive fertilization reduces playability and increases the risk of N leaching.
- Use soluble N sources (0.05-0.50 lb N per 1,000 ft2) to fine-tune clipping yield on highly managed turf surfaces.
- Fertilizer products with a blend of quick and slow-release fertilizer are frequently applied to non-intensively managed areas. Optimum timing for cool-season species is late summer through mid-fall; a secondary application can take place in mid-spring to early summer.
- Summer fertilizer applications can benefit young turf stands or stands growing on poor soils.
- Apply fertilizer when turf is actively growing to minimize loss.
- Light irrigation after P application has been shown to reduce P runoff.
- Maintain dense turf stand through proper nitrogen fertilization to reduce soil runoff.
- Monitor K and P by testing soil regularly.
- Prevent fertilizers from being deposited onto impervious surfaces.
- Avoid applying fertilizer to soil at or near field capacity or following rain events that leave the soil wet.
- Do not apply fertilizer when heavy rains are likely.
- Do not apply fertilizers to dormant turf or when ground is frozen.
- Maintain buffer areas around waterbodies. The buffer areas should not be fertilized.
- Choose the appropriate type of spreader for a given fertilizer.
- Calibrate application equipment regularly.