Employ cultural management practices that maximize nutrient uptake by plants, reduce nutrient waste and minimize off-site movement of nutrients.
Fertilization and supplemental irrigation are important in many turf management scenarios for the maintenance of an acceptable level of turf performance. Water, in particular, is an especially important consideration for effective nutrient management. Adequate moisture is critical for efficient uptake and use of nutrients, while excess moisture can lead to undesirable movement of nutrients in the environment. To protect precious environmental resources and to minimize maintenance costs, water and fertilizer inputs need to be kept to their lowest possible levels. This lower input can be accomplished in part by eliminating wasteful use and taking action to promote the retention of water and nutrients within the plant-soil system. Furthermore, by eliminating waste the turf practitioner can help to minimize the potential impact of nutrients such as phosphorus and nitrogen on surface and ground water quality. This can be done by enhancing the ability of turfgrass plants to acquire water and nutrients or equivalently, improving the nitrogen use efficiency (NUE) and water use efficiency (WUE) of the turfgrass system. Increased NUE and WUE helps to sustain greater turf quality and function under reduced water and fertilizer input.
Although NUE does not directly account for relationships involving other essential plant nutrients (such as P and K), NUE is an effective metric for evaluating the efficiency of various plant nutrients within a turf system. Remember that N forms the foundation of any fertility program for turf, therefore steps to improve N use efficiency by optimizing inputs and reducing waste will in turn promote efficient use and retention of other essential nutrients.
Correct factors that reduce soil infiltration and promote runoff.
- Low soil infiltration rates promote runoff and therefore may increase reliance on costly supplemental fertilization and irrigation. Whether the source of water is rainfall or irrigation, increasing the soil infiltration rate will reduce runoff potential, protect resources and promote turf quality.
- It is important to alleviate any condition or practice that reduces soil infiltration and promotes runoff:
- Manage excessive thatch and reduce soil compaction: Thatch can be hydrophobic, especially in summer, which can result in low soil infiltration rates. Compaction increases soil hardness and inherently reduces soil infiltration rates. These factors together inhibit rooting depth and density. These same conditions also promote surface water runoff as well as nutrient and pesticide losses, conditions that reduce plant and irrigation efficiency and compromise environmental quality.
- Do not irrigate in excess of the soils capacity to absorb water: Where slow infiltration is problematic, multiple cycling of irrigation may be necessary to prevent runoff.
- Water in fertilizer and nutrient containing materials immediately after application to move nutrients to the root zone, where they can be absorbed by the plant: Time fertilizer applications on un-irrigated lawns to coincide with subsequent rainfall whenever possible, avoiding applications prior to forecast periods of extended or excessive rainfall. Fertilize or apply nutrient containing materials in conjunction with core aeration whenever possible to further promote incorporation of fertilizers into the root zone.
- Protect steep slopes at establishment through use of mulches, netting or other appropriate material: If steep grades are unavoidable, then it is likely that multiple cycling of irrigation will be needed in such areas to prevent runoff.
- Employ appropriate cultural practices to maintain turf density: Decreasing shoot biomass translates to reduced capacity to inhibit water runoff.
- Manage heavy traffic: Turf thinning and soil compaction increase relative to the amount of traffic on the turf.
- Select and introduce turfgrass species and cultivars adapted for the site and use: Carefully selected, well-adapted species and cultivars have greater capacity to maintain turf function, shoot density and extensive rooting with less maintenance input in terms of fertilizer and water. Poorly adapted plants will be challenged to maintain shoot density sufficient to minimize runoff.
- Avoid excessive soil firming during establishment.
- Provide proper soil preparation at planting to minimize stones and debris at the soil surface.
Minimize leaching loss of water and nutrients.
- Soil water that moves below the rooting profile is water unavailable for plant uptake; such leaching loss is wasteful.
- Leaching events also move nutrients such as N and P below the root zone and out of the turfgrass system, which increases the potential for adverse environmental impact.
Alleviate factors that can lead to leaching of water and nutrient inputs:
- Avoid exceeding turfgrass evapotranspiration (ET) rates in summer: Irrigating deeply and infrequently according to ET replacement will help to prevent leaching loss.
- Avoid the use of highly water soluble N (WSN) fertilizers in summer: Use of slowly-available N (SRN) instead minimizes the potential for nutrient loss, especially on sandy soils that are prone to leaching. Fertilizer with at least 50% of total N as SRN is preferred (75% as SRN is better). Frequent spoon feeding or foliar N at very low WSN rates may be appropriate for more sophisticated systems.
- Maintain turf density: Thin turf has less photosynthetic leaf area to support sufficient root mass to enable effective uptake and utilization of water and nutrients.
- Do not apply fertilizers to dormant or inactive turf: Minimal shoot and root activity compromise uptake and utilization of water and nutrients.
- Promptly correct any practice that may result in removal or loss of nitrogen or water from the turf system.
Alleviate factors by that contribute to waste:
- Retain grass clippings whenever possible: Significant nitrogen and phosphorus is removed from turf systems by clipping removal, therefore the return of clippings to retain nutrients in the turf system is preferable in the vast majority of cases. When retaining clippings, supplemental fertilization must be adjusted to avoid possible overloads of N and P. Exceptions for removal of clippings include when they are excessive and may smother turf, when certain diseases are present, or during seed head formation of weed species. If clippings must be removed, dispose of them properly to avoid undesirable release and movement of nutrients as the clippings decompose.
- Direct applications of water and fertilizer to turf areas: Water and fertilizer that reach non-grassy areas and hard surfaces are not useful to turf and may be rapidly conveyed off-site, dramatically increasing the potential for negative environmental impact. Promptly clean up fertilizer as well as pesticide materials and turfgrass clippings that settle on impervious surfaces. Also, fertilizer and other nutrient containing materials should not be used as de-icers. Where irrigation is provided, water should only be applied to turf, not hard surfaces, and at a rate that ensures adequate infiltration.
- Properly calibrate fertilizer and irrigation delivery equipment: Irrigation audits and spreader calibration should be conducted regularly, consistently and correctly.
- Manage weeds: Undesirable grassy and broadleaf weeds compete with desirable turfgrasses for water and nutrients, therefore weed control/removal is important for improving efficient use of nutrients and water.
- Prevent nutrient deficiencies: Under-fertilized turf is less capable of mitigating losses of water and nutrients through leaching and runoff. Insufficient phosphorus (P) and potassium (K) may reduce NUE and WUE especially if rooting is inhibited. Furthermore, P should only be applied based on soil test results and soil testing for K is advisable as well.
Condition plants for nutrient uptake with responsible and effective cultural practices.
- Any practice that promotes rooting activity, especially in the deepest portions of the soil profile, will increase acquisition of both nutrients and water by turfgrass plants.
Alleviate factors that reduce turf system NUE and WUE by inhibiting rooting depth and density:
- Keep N inputs to the lowest possible level: This will promote greater rooting relative to shoot growth (high root-to-shoot ratio) and increase both NUE and WUE of turf.
- Manage excessive thatch and relieve soil compaction: These factors are inhibitory to rooting depth and density. These same conditions also promote surface water runoff as well as nutrient and pesticide losses, conditions that reduce plant and irrigation efficiency.
- Avoid excess levels of WSN and close height of cut: These practices in combination are more detrimental to rooting depth than either practice considered alone. SRN is more effective in increasing turf NUE and WUE compared to WSN (for example, a minimum of 75% of total N as SRN in summer is highly effective in minimizing shoot growth and alleviating root stress). Cutting too low, or too frequently, shrinks leaf area which translates into reduced photosynthetic capacity. Less photosynthetic capacity in turn can support less root mass and depth.
- Do not over-irrigate: Maintaining root zones at field capacity by over-watering will inhibit rooting, decrease drought resistance, and promote disease and soil compaction. Furthermore, excess moisture in the root zone can limit soil oxygen and affect active uptake of nutrients. Use of wilt-based irrigation (irrigation withheld until the onset of mild moisture stress) according to ET replacement will promote rooting and root activity and prevent leaching of water and nitrate-N. Wilt-based irrigation with ET replacement is very effective in enhancing NUE and WUE of turf.
- Manage soil pH: Acid soils (pH < 5.5) can inhibit rooting. Furthermore, availability of nutrients such as iron and manganese can reach toxic levels when pH is low. Follow soil test recommendations for adjusting soil pH to the slightly acidic to neutral range (6 to 7).
- Avoid shallow rooted species and cultivars: Plants with genetically limited rooting potential exhibit poor drought resistance as well as poor NUE and WUE. Generally plants with superior drought resistance have greater NUE. Use National Turfgrass Evaluation Program data (NTEP, http://www.ntep.org) for selecting drought hardy turfgrasses. See Section 4, Turfgrass Selection in this publication, for more information on the selection of turfgrasses.
- Take care with applications of soil applied preemergence herbicides: Some soil applied preemergence herbicides can negatively affect rooting of desirable turfgrasses. When a need for these type of materials has been identified as critical to the proper functioning of the turf, use a split application in spring to control weedy summer annuals such as crabgrass in two applications at reduced rates. Consult pesticide labels for split application rates that may be less detrimental to rooting without sacrificing season long weed control.
Establish new turf areas quickly and effectively while protecting soil and nutrients from loss.
Plant during favorable periods that promote rapid establishment.
- The ideal period for establishment in the Northeast is late summer to early fall.
- Consider using grasses that establish quickly, such as perennial ryegrass, to promote rapid grass cover when needed. This is especially important on slopes or in environmentally sensitive areas to minimize soil loss and potential environmental contamination.
- Avoid excess firming of soil.
Take steps to prevent movement of soil off-site.
- Eliminate potential for storm water runoff; keep soil from running onto hard surfaces or into catch basins.
- Consider sodding areas that have a high erosion potential during the establishment phase. Sod should only be installed if irrigation is available throughout the establishment phase.
- Take all available steps to maximize turfgrass germination and rapid establishment. Mature turf has a much greater capacity to hold soil in place and prevent erosion.
Promote rapid establishment with mulches and similar materials.
- Consider using mulches or erosion control blankets to promote soil infiltration of water, to reduce soil loss, to buffer temperature fluctuations and to hasten germination.
Promote rapid establishment with proper fertility.
- Proper fertility at establishment greatly reduces the potential nutrient losses over time.
- Phosphorus (P) needs by the turfgrass plant and rates of P fertilization are greatest during the establishment period. Apply P as recommended by a soil test.
- N and P losses can be greater at establishment due to low shoot density, use of readily-available nutrient sources, and high irrigation frequency. Therefore, providing conditions for rapid establishment and protecting soil from loss are critical.
Keep application records for fertilizer and nutrient-containing materials.
Maintain detailed application records as a useful tool for evaluating and adjusting the fertility program.
- Good records are invaluable for evaluating the performance of an existing fertility program, as a guide when making adjustments, and as a reference from season to season.
The following information is suggested for fertility records:
- Application location
- Presence of and distance to surface water, wellheads or other environmentally sensitive areas
- Soil type
- Date of most recent soil test
- Product or material applied
- Nutrient analysis of material
- % slowly-available N (SRN as WIN or CRN)
- Amount of material used and timing
- Application equipment used (drop, rotary, spray)
- Application rates used for N, P2O5 and K2O
- Wind speed at application
- Rainfall amounts 24 to 48 hours before/after application
- Magnitude and length of slope of fertilized area
- Total annual N used
- Total annual P used
- Total annual K used
- Other comments/notes