7 Cultural Practices
Cultural practices support turfgrass density and therefore play an important role in preserving and protecting water quality. Ensuring that the turf is properly adapted, healthy, and dense and has adequate infiltration protects water quality because of the tendency of healthy turf to hold water and chemicals.
In particular, BMPs for golf course turf to preserve and protect water quality using cultural practices must be designed to sustain high turf shoot density. A dense turf reduces runoff and the negative effect of off-site movement of water and pollutants. A dense turf, however, accumulates surface organic matter that can restrict infiltration and lead to increased runoff. Maintaining the permeability of the turf surface is as important as maintaining turf density. Strategies for preventing excessive organic matter accumulation are important, but management through dilution and cultivation of the soil is key. This practice can include modifications to improve the root zone, balance adequate infiltration as means of reducing runoff, and promote adequate retention to prevent leaching.
BMP Principles for Cultural Practices
- Use and manage turfgrass species and varieties adapted to macro and micro climatic conditions of your location.
- Maintain turf with high shoot density to minimize runoff and maximize infiltration.
- Manage the surface accumulation of organic matter to maintain a permeable system that minimizes runoff and maximizes subsurface retention.
7.1 Turfgrass Species and Variety Selection
The perennial nature of golf turf implies that when establishing or renovating a new turf area, it is critical to choose a well-adapted species and variety. Of course, putting surfaces are unique growing environments, but larger areas such as fairways could have grasses adapted to reduced nutrient levels and increased traffic tolerance, potentially reducing the nutrient loading. This is an important BMP for nutrient management. Additionally, natural areas that serve as landscape BMPs also require careful attention to finding a well-adapted species. Certain grasses adapted to low inputs, reduced mowing, and even submersion tolerance can be part of the selection criteria. Ultimately, it is vital to start out with a well-adapted species that will thrive, meet the functional and visual quality expectations, and be sustained using BMPs.
7.1.1 Species Selection
When selecting species and cultivar, site specific characteristics, such as desired use, site and microclimate conditions, disease resistance, drought tolerance, and spring transition traits, should be considered. To evaluate different species and identify cultivars that perform well in this region, extensive trials are conducted under the National Turfgrass Evaluation Program (NTEP). Results of NTEP trials conducted and evaluated by Cornell are available on the NTEP website.
Highly specific and often less than ideal microclimate conditions challenge many superintendents. A common microclimate is a putting surface location with light deficits and restricted air movement. In these situations, limited options exist for proper turf selection, as these climates simply cannot sustain any turf without significant inputs. Typically, in northern climates, these adverse site conditions lead to increases in weedy species such as annual bluegrass.
7.1.3 Annual Bluegrass Invasion
Over time, annual bluegrass becomes the dominant species in turf. This invasiveness is a result of the highly adaptive and prolific reproductive capacity of annual bluegrass that favors its competitive ability over other cool season turfgrass. Therefore, regular surface disruption when desirable turf is not actively growing selects for the invasive annual bluegrass. Every course that suffers a massive invasion of annual bluegrass must decide whether to renovate or manage typically when there is catastrophic failure. Renovation eradicates and then excludes annual bluegrass, hopefully with proper site modifications to allow perennial species to thrive. Others choose simply to manage the annual bluegrass that has colonized the location. This is a “pay me now or pay me later” situation in which management of the problem is less disruptive, though the inputs required to sustain adequate turf are costly.
Research shows that annual bluegrass requires courses to use significantly more inputs to provide acceptable quality golf turf, especially on putting greens, as compared to more perennial species such as bentgrass or fescues. Therefore, with respect to water quality protection, the less annual bluegrass being managed, the fewer inputs required and the lower the risk to water quality. While this solution may not be as practical on putting surfaces, the putting surfaces comprise less than 10% of the managed turf. It is fairway, rough, and tee areas where annual bluegrass challenges water quality preservation with large tracts of land being treated to sustain a weedy species.
7.2 Turfgrass Establishment
Establishing new turfgrass areas or renovating existing stands can create significant risk to water quality. During establishment, soil is exposed prior to seeding or sodding to ensure effective contact for water transfer from the soil to the plants. Therefore, practices should be implemented that reduce establishment time to full turfgrass cover and protect the soil from being transported in rain events during establishment.
7.2.1 Erosion and Sediment Control During Establishment
The loss of topsoil from a site can be a problem for numerous reasons. Soil carried by wind and water transports contaminants with it. For example, erosion can enrich surface water, where phosphorus, and to a lesser extent nitrogen, can cause eutrophication. When sediments and soils enter water, they can also increase turbidity, which can have harmful effects on aquatic plants and animals. Therefore, control measures should be documented in an erosion and sediment control plan, put in place prior to any soil disturbance, and properly maintained.
7.2.2 Nutritional and Irrigation Needs
Minimizing the amount of fertilizer and chemicals used during the establishment phase is critical, as the establishing turf does not provide the needed uptake to prevent runoff and leaching. Newly establishing areas, especially from seed with soil exposed, should be irrigated carefully. Light, frequent amounts of water to keep the seedbed moist will encourage germination and seedling development. Once the turf density reaches 60-70% cover, irrigation can be reduced to more normal levels, as turf will begin to root and extract water and nutrients from the soil.
7.3 Maintaining Turfgrass Density
Turfgrass runoff research consistently concludes that maintaining high shoot density turf is the most effective means of reducing runoff volume. The distance traveled by rainfall or irrigation water increases as the number of shoots per unit area increases. In addition to the reduced runoff, the fibrous root system of turf has been shown to increase infiltration. The longer the water deposited on the turf surface is delayed from becoming runoff, the more likely that proper infiltration will occur. The combination of reduced runoff volume and increased infiltration is a primary aspect of water quality protection, thus maintaining a dense turf is vital. In addition, denser turf also provides a better playing surface.
A turf is defined as low growing vegetation maintained under regular mowing and traffic. Conversely, areas not regularly mowed are not considered turf. Mowing is a significant selection tool and one that, when done properly, has a profound influence on turf density. A properly mowed turf maintains a high shoot density that limits surface water movement and sustains an adequate underground biomass to retain additional water and nutrients that infiltrate. Mowing practices require decisions regarding height, frequency, type of mower, and clipping management. Individually and collectively these practices, when performed properly, maximize turf density.
Height of cut is often determined by the function of the site, with additional emphasis on visual quality. Mowing height significantly affects rooting depth because the lower the turf is mowed, the shorter the root system, and therefore the greater concentration of surface rooting. Additionally, a lower height of cut requires more frequent mowing as leaf extension accelerates when turf is cut lower and tissue must be removed more frequently.
Ultimately, every turfgrass species has an ideal mowing height range and a mowing range that the species can tolerate. Maintaining turf within the ideal range maximizes density. As long as mowing heights remain within the tolerance range, however, adequate density is possible when other maintenance factors such as water and nutrients are provided in the optimal range.
The turf growth rate and height of cut dictate mowing frequency. In general, increasing mowing frequency increases turf density. Little evidence supports the accepted rule that no more than 30% of the leaf tissue should be removed in a single mow. Instead, significant evidence indicates that some turf species such as tall and fine fescue and perennial ryegrass can have between 50 and 75% of the tissue removed before any turf thinning occurs. Ultimately, increasing mowing frequency positively effects turf density, but will increase the energy consumption of the maintenance program.
Mower selection is based on the expected height of cut. Mowing heights at or below 1.5 inches are typically best achieved with a reel-type mower. Reel mowers allow for rapid clipping of turfgrass tissue at practical operating speeds with minimal turf damage (when properly adjusted). Mowing heights above 1.5 inches are best achieved with rotary impact mowers, also when blades are sharpened and properly balanced.
Any mistake in mower set up from blade sharpness to bedknife alignment can lead to increased stress from wounding and reduction in turf density. Therefore, the mower must be properly adjusted and set up to minimize leaf shredding and wounding for pathogens.
7.3.2 Clipping Management
From a water quality perspective, grass clippings are a nutrient-rich resource and should be viewed as fertilizer and handled and applied with similar precaution. For example, clippings may account for 0.10 to 0.35 lbs P per 1,000 sq. ft. When managing clippings, consider them a nutritional resource and leave them on-site if possible. However, they must not be allowed to discharge into adjacent waterbodies or to clump on the surface and shade the turf.
Removal of clippings should only be performed if the function of the site dictates removal (such as ball roll on a putting surface). Some courses will remove clippings from fairways, distributing these clippings, such as to driving ranges or clubhouse lawns, or composted. When clippings are distributed, the area should be relatively large, as accumulated clippings distributed over a relatively small area can significantly increase nitrate leaching. If clippings are composted, the compost area should not be located near stormwater treatment structures or wetlands. For further information on composting, see the fact sheets published by the Cornell Waste Management Institute.
7.4 Organic Matter Management
Turf is a perennial plant system that increases biomass as a result of growth and management. Biomass accumulates at the surface from the development and deposition of plant parts such as leaves, stems, and roots. Above-ground plant parts such as leaves and stems are often removed and regrown as a result of frequent mowing. Underground plant parts such as stems (rhizomes) and roots cycle as living, dead, and decomposing organic matter.
The accumulation of organic matter in the top 3 to 6 inches of a turf system provides nutrient and water holding as well as cushioning and insulation. When organic matter accumulates at a rate greater than it degrades, however, it can restrict infiltration of water and gas exchange between the atmosphere and the pore space in soil. Excessive organic matter at the surface can become hydrophobic and increase runoff from the turf surface, which may also reduce the effectiveness of fertilizers and pesticides. Furthermore, excessive surface organic matter can promote surface rooting that interferes with the turf’s use of water and mineral nutrients, which leads to increased potential for off-site movement of chemicals applied to turf. Many factors influence the accumulation of organic matter including turfgrass species, fertilization, and soil physical and chemical properties.
7.4.1 Grass Type
Creeping bentgrass and annual bluegrass are considered intermediate in their development of organic matter. They accumulate organic matter, but often that matter is not highly lignified tissue and, under warm moist soil conditions, it degrades. Still, these grasses accumulate organic matter at the surface at a rate greater than microorganisms can degrade and thus the accumulation requires dilution or mechanical removal.
Increase in biomass is a normal aspect of plant growth. Supplemental fertilization for functional and aesthetic purposes produces more biomass and more organic matter when compared to an unfertilized turf. The rate of decomposition also increases with supplemental fertilization, up to a point. Therefore, applying enough fertilizer to meet the visual and functional requirements of the turf, but not in excess of these requirements, is critical. Excess fertilization increases biomass production that leads to excess surface organic matter production, reduced infiltration, and increased runoff.
Organic matter is a food source for macro- and microorganisms. The soil food web requires an adequate amount of organic matter and microbial activity to function properly. Degradation of organic matter is maximized in a well-aerated, moist soil with temperatures greater than 65°F. For every ten degree Celsius increase in soil temperature, microbial activity increases tenfold; this principle is referred to as the “Q10”.
7.4.3 Soil Management
Poorly drained soils with high bulk density and predominance of fine particles that restrict soil gas exchange reduce microbial activity. These dense, cool soils also restrict rooting to the surface, which further exacerbates the surface organic matter problem. Maintaining a permeable soil surface sustains adequate microbial activity, good deep root development, and proper infiltration. Taken together, these practices lead to a turf surface less likely to create runoff and more able to retain chemicals applied to turf top prevent leaching.
7.4.4 Cultivation Practices
Cultivation practices – aeration practices and surface cultivation practices – disturb the soil or thatch through the use of various implements to achieve important agronomic goals that include relief of soil compaction, thatch/organic matter reduction, and improved water and air exchange. However, cultivation can require significant time for recovery, thus disrupting play, and should be used judiciously. Cultivation frequency should be based on traffic intensity, level of soil compaction, and the amount of accumulation of excessive thatch and organic matter, which reduces root growth, encourages disease, and creates undesirable playing conditions. Table 2 shows advantages/disadvantages of aeration practices.
Table 2. Aeration practices
|Method||Compaction relief||Surface disruption||Water/air movement||Disruption of play|
|Hollow-tine aeration||High||Medium||High||Medium to High|
|Solid-tine aeration||Low||Low||High||None to Medium|
|High-pressure water injection||None||Low||High||None to Low|
Surface cultivation manages organic matter accumulation above the soil, reduces the formation of leaf grain, improves infiltration, and improves surface consistency (Table 3). While these methods are generally less disruptive than traditional aeration practices, they usually have a limited to no impact on soil compaction relief.
Table 3. Surface cultivation practices
|Method||Compaction relief||Surface disruption||Water/air movement||Disruption of play|
|Vertical mowing||Low||Medium – High||Medium||Low – High|
|Grooming||None||Very low||Very low||None|
Managing surface organic matter is best accomplished by prevention through proper fertilization and soil management. Many common golf turf grasses, however, under routine maintenance and adequate prevention still produce organic matter that requires some level of management. The most effective means of managing surface organic matter is through regular applications of sand or soil via topdressing. A light (0.1 to 0.2 inches) amount of material applied and integrated into the surface of the turf dilutes the organic matter and creates a physical matrix that functions as a soil.
Topdressing is often performed in conjunction with some form of cultivation that either removes a core or makes a hole. The cultivation not only provides minor removal of the surface material but also creates space for topdressing to serve the purpose of dilution and creation of a pseudo-soil matrix.
Recent research suggests that under normal golf turf management, creeping bentgrass putting surfaces require 18-22 cubic feet of sand per 1,000 sq. ft per year to properly dilute surface organic matter. This application requires topdressing as frequently as every five days without any cultivation, to as many as 14 to 21 days with more routine cultivation. Ultimately, the goal of proper dilution is to ensure adequate infiltration while preserving sufficient retention of the turf system to prevent leaching.
7.6 Cultural Practices Best Management Practices
Turfgrass Species and Variety Selection
- Select species and cultivars that are adapted to the desired use, taking note of disease resistance, spring transition and greenup, drought tolerance, and other traits such as shade and wear tolerance utilizing NTEP data.
- Ensure erosion and sediment control devices are in place and properly maintained when establishing new turfgrass stands.
- Use mulch (e.g. hydromulch, loose straw from a clean source, strawmats) for soil stabilization.
- Prepare seed/sod bed to maximize success.
- Fill gaps in sod seams with soil or sand to provide a uniform surface.
- Use selective pre-emergence herbicides to reduce weed competition and improve the chance of success with seeding establishment during the spring.
- Use light and frequent nutrient applications, unless a slow-release nitrogen source is applied.
- Mow turf to the desired mowing height as soon as practical to promote density and maturation.
Maintaining Turfgrass Density
- Raise HOC by at least 30% in heavily shaded areas to improve turf health.
- Increase HOC in times of stress such as heat, drought, or prolonged cloudy weather to increase photosynthetic capacity and rooting depth of plants.
- If turf becomes too tall, it should not be mowed down to the desired height all at once. Tall grass should be mowed frequently and HOC gradually decreased until the desired HOC is achieved.
- Mowing frequency should increase during periods of rapid growth and decrease during dry, stressful periods.
- Rarely use inefficient mowing patterns (e.g. 9-3) on areas other than putting greens to save time, fuel, and labor.
- Use proper mowing equipment.
- Regularly sharpen and adjust blades.
- Routinely use plant growth regulators, if needed, to improve overall turf health in shaded environments.
Organic Matter Management
- Incorporate a proper cleaning protocol for cleaning mowing and grounds equipment when working in areas with terrestrial invasive species.
- Return clippings to turf as a practical method of returning organic P and N back to the soil.
- Remove clippings only if the function of the site dictates removal (such as ball roll on a putting surface).
- Accumulated clippings distributed over a relatively small area can significantly increase nitrate leaching, therefore distribute any collected clippings to driving ranges, clubhouse lawns, or compost.
- Clippings can be a significant source of phosphorus and nitrogen movement off-site, and thus should not be placed in or near stormwater treatment structures or wetlands.
- When organic matter levels are excessive, core aeration programs should be designed to remove 15- 20% of the surface area and to minimize grain formation.
- High-traffic areas may require a minimum of two to four core aerations annually.
- Core aeration should be conducted only when grasses are actively growing to aid in quick recovery of surface density; midsummer for buffalograss and spring/fall for cool season grasses.
- Aeration events should be as deep as practical to prevent development of compacted layers in the soil profile as a result of cultivation.
- Consider timing of core aeration to avoid time of Poa annua (annual bluegrass) seed head formation.
- Backfill holes with new root-zone materials if a drill-and-fill machine is used.
- High pressure water injection can be applied once every 3-4 weeks throughout the summer.
- Initiate vertical mowing when thatch level reaches 0.25-0.5″ in depth. Shallow vertical mowing should be completed at least monthly on putting greens to prevent excessive thatch accumulation.
- Vertical mowing depth for thatch removal should reach the bottom of the thatch layer and extend into the surface of the soil beneath the thatch.
- Aggressive or deep vertical mowing should not be used when the turf is growing slowly.
- Frequent shallow vertical mowing on putting greens prevents excessive thatch buildup and grain formation.
- Use light and frequent topdressing applications following aeration.
- Creeping bentgrass putting surfaces will typically require 18-22 cubic feet of sand per 1,000 sq. ft per year to properly dilute surface organic matter.
- Use sand particle size distribution similar to the existing soil, to avoid layering.
- Know the sand source and ensure the sand is weed-free, uniform, and of appropriate quality.