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Developing a Fertility Program

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objective

Determine the level of nutrition necessary to achieve acceptable turf quality

Consider the ultimate uses of the turf, and expectations for quality and performance.

  •  Adequate and balanced nutrition is essential to maintaining a healthy turfgrass shoot and root system.
  •  Heavily used and/or intensively managed turf (for instance, athletic fields and golf course greens) often requires more nutrition than residential lawns and utility turf.
  •  High profile or heavily used lawns will require more nutrition than less heavily used lawns with lower quality and functional expectations.
  •  Adequate fertility is critical for maintaining function, managing stress, and recovering from damage.
  •  A dense, properly fertilized turf is more likely to capture, retain and use nutrients more efficiently than under-nourished turf.

Identify the grasses present on the site as well as the desirable grasses for the site and use.

  •  There can be significant variation in terms of nutritional requirements between species and even among individual cultivars within species.
  •  Grass species and cultivars unadapted to site conditions often require additional nutrition to help 'bridge the gap' and achieve acceptable performance.

Consider the growing environment on the site.

  •  Existing factors such as shade, pH, thatch, poor drainage, proximity to environmentally sensitive areas or to heat islands, and other factors can significantly modify the nutritional requirements of the turf. 

Assess the soil type and condition on the site.

  •  Soil type affects nutrient-holding capacity and nutrient retention characteristics.
  •  Sandy soils low in organic matter are prone to leaching and generally have a low nutrient reserve.
  •  Loamy soils with organic matter (humus) and some clay content are less prone to leaching and generally have a higher nutrient reserve. Nutrients can also bind to soil particles or organic matter and become less available. 
Sandy Soils Loamy Soils
  • low nutrient reserve
  • poor nutrient and moisture retention
  • potential for high nutrient losses via leaching
  • generally more fertile
  • good nutrient and moisture retention
  • potential for significant content of unavailable nutrients 

Manage soil pH appropriately.

  • pH management is crucial, as pH extremes have implications for solubility (availability) of nutrients.
  • pH in the slightly acidic to neutral range generally maximizes nutrient availability.
  • Managing pH is often the best way to avoid micronutrient deficiencies.
  • Maintaining proper pH is important for preventing build-up of unhealthy amounts of thatch.

To maximize nutrient availability, make provisions for sufficient moisture.

  • Plants take up mineral nutrients in solution, therefore adequate moisture is required for nutrient release from most fertilizers and mineralization of nutrients from organic matter.
  • Less moisture makes nutrients less available to plants and less mobile in soil.
  • Excess moisture, however, can facilitate nutrient loss via leaching and runoff.
  • Adequate moisture is especially critical at establishment, not only for seedling growth and development, but also to enhance nutrient availability.

Understand and encourage soil microbial activity.

  • Microorganisms impact fertility by decomposing organic material, mineralizing nutrients, recycling and immobilizing nutrients and fixing and transforming nitrogen.
  • Soil microorganisms are most active when soil moisture is adequate, when soil temperature is greater than 55º F, when soil is well aerated and when soil pH is near neutral (6.5-7.0).
  • Microorganisms get their energy from carbon (C) sources. Like plants, they also require nitrogen (N) and can often acquire it more easily than plants.
  • Microbial populations and activity can be promoted by maintaining adequate soil moisture, optimum pH, balanced fertility, good soil aeration, by limiting use of pesticides and growth regulators, and by using organic amendments with readily available C and N.
  • Microorganisms will tie up N when decomposing materials with a carbon to nitrogen ratio (C:N) > 30:1. If such materials (e.g. inadequately decomposed woodchips or compost materials) are present in the soil, then additional N may need to be applied to avoid weak, stunted turfgrass growth. Preferably, soils containing such materials should not be used until the high C:N ratio components are more thoroughly decomposed.

Understand that nitrogen (N) is the foundation of any fertility program for turf.

  • N is needed in the greatest amount because of its many effects on turfgrass growth.
  • Adequate nitrogen is necessary to maintain high shoot density, realize vigorous but not excessive growth, attain healthy moderate green color (which is an indicator of the potential for photosynthesis, the process by which the plant produces its energy), and the ability to recuperate from stress or pest injury.
  • Excessive N can increase disease problems, reduce tolerance to high and low temperature, reduce traffic tolerance and result in moisture stress due to increased shoot growth and reduced rooting.

Know that phosphorus is needed by turfgrass plants in amounts second only to N.

  • Phosphorus is essential when establishing new turf plantings, and also helpful in improving both rooting and winter hardiness.
  • Adequate phosphorus in the seedbed is critical to rapid establishment and to reduce runoff following planting.

Provide adequate potassium.

  • Adequate K fertility improves wear tolerance, heat and cold tolerance, stolon and rhizome growth, and rooting (thus improving water and nutrient uptake).
  • Unlike N and P, K is an environmentally-benign nutrient and excess K fertilization poses little to no known risk to human health or the environment.

objective

Develop a sound plan for additions of nutrient- containing materials into the turf system; these are some of the most important and complex decisions a turf manager makes.

Develop and implement an efficient nutrient management plan that prioritizes environmental protection:

  • Perform site analysis with identification and mapping of environmentally sensitive areas as well as areas at high risk for off-site movement of nutrients. 
  • Note and map specific buffer zones delineated in environmentally regulated areas such as Zone I Wellheads, wetlands and certain coastal zones, and for protection of natural resources.
  • Map, including measured square footage or acreage, areas being fertilized or receiving nutrient containing materials.
  • Perform and consult soil tests to determine soil water infiltration and drainage characteristics.
  • Reduce applications of nutrient-containing materials to the lowest possible level required to sustain an acceptable level of turf performance.
  • Implement cultural practices that maximize nutrient uptake by plants, reduce nutrient waste and minimize off-site movement of nutrients, especially by reducing soil compaction, increasing surface water infiltration, and decreasing runoff.
  • Implement proper storm water management techniques aimed at reducing movement of soil and nutrients.
  • Apply fertilizer and other nutrient containing materials so that they do not land or stay on hard surfaces and so that they do not enter surface waters or conduits such as catch basins that lead to surface waters.

Understand that there is no generic fertility program that will produce excellent turf under all conditions.

  • Factors that may vary among different fertility programs include the form of nutrients to be applied, the frequency of application, the rate of application, the timing of applications throughout the season and the placement of the fertilizer and other nutrient containing materials.
  • Factors including turf quality desired, use of the turf, site conditions, grasses present, age and maturity of the turf stand, resources available, proximity to environmentally sensitive areas and other factors will influence the frequency, rate, timing and placement of applications of the particular nutrient sources to be applied.
  • Select fertilizer and other nutrient containing materials appropriate for the time of year, irrigation status of the turf, and growth rate of the grasses present.
  • Recognize that improper fertilization practices can be more detrimental than not fertilizing at all.
  • On established turf, N and P losses from unfertilized areas can be equal to or greater than losses from fertilized areas.

Fertilize for the right reasons.

  • Adequate and balanced nutrition is critical for healthy turfgrass shoots and roots.
  • Apply fertilizer to the turf system to supply nutrients that may be in inadequate supply for the desired level of turf performance.
  • Vigorously growing turf is more resistant to weeds, disease, and insect pests.
  • Healthy turf provides a surface better able to withstand wear as well as mechanical and environmental stresses.
  • Dense, well-rooted turf promotes water infiltration and effectively mitigates runoff.
  • Good nutrition helps to promote turf with favorable aesthetic characteristics.

Give some low maintenance turf areas special consideration in terms of fertility.

  • Although turf use factors and even aesthetics are not necessarily a priority for management of many low maintenance sites, all turf requires some minimum level of fertility to provide other functional benefits such as erosion control, atmospheric carbon sequestration, slowing of runoff, and promotion of moisture infiltration.
  • A soil test is the best starting point for selecting an appropriate fertilizer material and determining a reasonable rate.
  • Use caution when considering fertilization for sites that have not been fertilized for several years. Certain older, low traffic and very low maintenance sites have achieved an acceptable equilibrium that may be disrupted by new fertilizer input. Unless expectations have changed or issues with growth rate or stand density are apparent, sometimes it is best to leave such sites alone in terms of fertility.