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Improving the water, reducing the chemicals – how to improve golf’s environmental footprint

NanoOxygen Systems
Macro, Micro and Nanobubbles

A Golf Digest poll was conducted in two  segments – all golfers (350 respondents) and a  combination of golfers and non-golfers (650).  Over 1000 interviews were conducted over  the phone and a telling statement reflected  some differing opinions (Barton, 2008): 

“Golf is an environmentally friendly /  compatible sport”. 

  • 91% of golfers agreed 
  • 66% of non golfers agreed 

Many believe golf courses use too much  water, leach excessive amounts of fertilizer to  the groundwater and surface water, and use  synthetic chemicals such as pesticides  (herbicides, insecticides, and fungicides)  indiscriminately. Again, this is the perception  and if anything, it’s probably become more  pronounced today.  

In this article we are going to discuss new  technology that has been developed that can  directly impact chemical inputs and the  environmental footprint of golf courses. Our  focus is on the water used on turf, more  specifically, the oxygen in the water.  

Water Use and Water Quality

Water is the largest input applied to a golf  course and so it has a significant impact on all  aspects of agronomy. The best quality water  available for turf comes from the sky – void  of most problematic chemicals and with a  good oxygen level. Once rainwater is  captured and stored or contacts the ground, it  becomes contaminated with minerals,  chemicals, organics, etc. and can begin to  negatively impact soil health.  

When superintendents are asked how their  turf quality looks after a good soaking rain –  most reply it’s the best they’ve seen in a long  time. Why? Rainwater is generally slightly  acidic in pH and has no bicarbonates or salts  that inhibit soil microbiology. In fact,  rainwater can effectively flush green  complexes – washing away many soil  chemistry problems such as high sodium  content. 

Rain has between 8-10 ppm of dissolved  oxygen (DO) which is obtained as it passes  through the atmosphere on its way to Earth.  It’s the dissolved oxygen in the water that is  the critical measurement of water quality as it  impacts almost all the biological activities in  the soil. And yet, few measure the DO in their  water. Water chemistry is the focus, driven by  the need to adjust ions and molecules to  change soil conditions – maybe driving the  overdosing chemical perceptions of golf? 

Irrigation water sources used in golf courses  include city/potable water, well water,  reclaimed water, rivers, ponds, and lakes.  Each of these sources has their own unique  water chemistry and impact on soil health.  For this discussion we’re going to focus on  the dissolved oxygen levels of these irrigation  sources – most of which are low and  problematic compared to rain water. 

US golf courses use approximately 2.1 billion  gallons of irrigation water per day. Many  courses have more than one source of water  for irrigation, over 50% is sourced from  ponds or lakes and another 46% from  groundwater or wells. Municipal reclaim  water from wastewater treatment plants  accounts for only 12% of all irrigation water  supply (Lyman, 2012) With most of the  irrigation water coming from potentially low  dissolved oxygen sources, it’s important to  understand what low DO levels are and how  they impact soil health.  

Water dissolved oxygen level is expressed as  parts per million (ppm) or milligrams per liter  (mg/L). Ranges of DO and the impact on plant health are: 

  • Highly saturated > 15 ppm. Great for plant  health. Hard to obtain with air. Normally use  oxygen or ozone injection to achieve this level  of DO. Can occur in upper portions of ponds  with full algae blooms (photosynthesis). 
  • Good quality = 8 ppm. Oxygen can be released  into the root zone and raise plant metabolic  activity. Plants are generally healthy. Low  disease pressure.  
  • Acceptable = 6 ppm. Oxygen will keep plants  alive. Some pockets of concern if water fills  soil air pore space. Can create favorable disease  conditions. 
  • Hypoxic < 4 ppm. Severe oxygen deficiency  that is very harmful to plant health and can be  fatal to turf. Creates significant disease  pressure.  
  • Anoxic <1 ppm. Oxygen-deficient and  negatively impacts soil life. Should not be used  for irrigation purposes. 

Typical irrigation water dissolved oxygen @ 20 deg. C 

Related: Superintendent Predict the Future of Your Irrigation Ponds with Bathymetric Mapping

Irrigation Sources DO level
Well water/groundwater0-2 ppm
Pond/lake (surface)4-10 ppm
Pond water (bottom)0-2 ppm
Reclaimed water1-6 ppm
Streams/rivers (moving)6-8 ppm
City/potable water5-8 ppm 

Surface water intakes are recommended on  ponds that are stratified to reduce the  potential for low DO water and sediment  from the bottom to be sent to the turf. (Smart,  1999). During the daylight hours when algae  are producing oxygen, irrigation water DO is  elevated (along with algae levels). At night  algae consume the oxygen they made during  the day – resulting in lower DO irrigation  water still being sourced from a floating  intake system. This is especially acute if a  course is irrigated just before daybreak when  dissolved oxygen is at its lowest. 

How does low DO water impact turf?  
Typical soil components

How does low DO water impact turf?  

Turf respiration enables plant roots to absorb  soil oxygen, water and nutrients and transport  them to plant tissue. Soil is made up of  roughly 50% solid material/minerals and the  rest water and air or pore space. Plant roots  absorb oxygen from the pore space and  oxygen dissolved in soil moisture, using it  like animals do in breathing.  

The soil environment is impacted when soil  pore (air) spaces are filled with water. When  the water contains high levels of dissolved  oxygen, it is more suitable to support soil  health and plant growth. If water oxygen is  low, oxygen can be displaced from the root  zone, the pore spaces become saturated and  plant health starts a serious decline. Studies have shown that when irrigation water is low  in DO, soil oxygen will pass into the water  and DO can actually be lost to the soil profile  and drained away – making the problem even  worse. 

Anaerobic soil generally has a black color and  can emit a hydrogen sulfide / rotten egg odor.  As free oxygen is lost, sulfates in the soil are  reduced to sulfides and can form what is  commonly referred to as “black layer”. This  anaerobic zone in the soil causes a loss of root  mass, poor nutrient uptake, and declining turf  health. Turf thinning, especially in the  summer, can be a direct result of black layer.  High plant respiration rates during periods of  higher temperatures and humidity cause an  oxygen demand in the soil that can’t be  achieved with low DO water. 

Once the root zone oxygen level is depleted,  and turf health declines, it only rebounds  when the soil dries out and the pore spaces  are reopened or when higher dissolved  oxygen water is provided (rainfall). This  cycle continues on many irrigated golf  courses and has a significant impact on the  increased use of fertilizers and pesticides to  combat this anaerobic soil condition. 

Many irrigation ponds contain blue green  algae or cyanobacteria. This is especially a  problem in the summer months when  nutrients in the bottom muck are released into  the water column, feeding the algae. When  this water is used for irrigation, cyanobacteria  are spread on the turf and cause yellow spot  and other issues. 

Thin turf can be crusted or matted with blue  green algae which negatively impacts turf  recovery. Additionally, blue green algae create an anaerobic environment and directly  cause black layer as sulfides are reduced in  the soil. Cyanobacteria release toxins into the  soil that cause chlorosis. Efforts to reduce  cyanobacteria should start with the source –  reducing the blue green algae levels in the  irrigation pond by introducing oxygen that  migrates to the bottom and reduces  phosphorus release. (Tredway, 2006) 

How Low Water Dissolved Oxygen  Levels Impact Chemical Use

Fertilizers 

Nitrogen, Phosphorus, and Potassium are  required by plants in order to ensure healthy  and sustainable growth. Soil bacteria are  aerobic organisms. They need oxygen to  survive and respire. Soil oxygen levels  determine and impact bacteria population  levels. Both bacteria and fungi microbes  utilize soil nitrogen to decompose carbon in  the soil. Protozoa and nematodes consume  these microbes – releasing nitrogen to the  plant in the form of ammonia.  

Under oxygen rich environments,  Nitrosomonas and Nitrobacter bacteria  convert ammonia into free nitrates in the soil.  Free nitrate is then utilized by the plant. This  has to be done in an aerobic environment and  is the primary pathway for nitrogen  assimilation into plants.  

If the soil is oxygen deficient, denitrification  occurs. Soil microbes use nitrate and nitrite as  the terminal electron acceptors for respiration  (instead of oxygen) and even sulfate when no  more nitrate is available (black layer) . Again,  when turf is watered with low DO water, soil  pores become filled, and the soil profile can  become oxygen limiting (Horgan, 2003). As  soil temperatures rise, nitrogen losses  increase as the turf’s elevated respiration  triggers more denitrification and a decreased  efficiency in fertilizer use. The result of this  biochemical reaction is evolution of the  nitrogen as N2 gas – resulting in loss of N  from the soil to the atmosphere. 

Phosphorus is used in a plant for collecting  the sun’s energy and completing  photosynthesis by converting it into plant  energy that is used for cell development and  reproduction. It is an essential element for  plant growth and is a component of RNA and DNA.  

Approximately 30-60% of phosphorus in the  soil is in an organic form which is not plant  available. Organic phosphorus includes dead  plant and animal residue, soil  microorganisms, and stored P in algae and  other decaying material. Aerobic soil  organisms are used to process organic forms  of P into inorganic forms which can be used  by the turf – a process called mineralization.  

The form of phosphorus most readily  accessed by plants are orthophosphate ions  that are assimilated into the plant via  diffusion. This requires a higher level of P in  the soil than in the roots to drive the P into the  plant. By ensuring a healthy microbial  community in the soil to assist in efficient  orthophosphate conversion, less supplemental  P is required to be added to turf.  

Golf courses must manage inorganic  phosphorus fertilizers closely. Insoluble  phosphorus that is not taken up by the plant is  typically washed down the soil profile and  drainage system or into the water table,  stormwater pond, wetlands, or adjacent  stream. In that case – this nutrient runoff can  be a major cause of algae blooms and  deteriorating surface water quality,  sometimes negatively impacting a golf  course’s own irrigation pond.  

Another reason for turf managers to ensure  good water quality and adequate dissolved  oxygen is to avoid the high cost of  supplemental fertilizers. Since the beginning  of 2020 the cost of nitrogen fertilizers has  increased nearly 4 fold with P & K up nearly  3 fold. Improving soil health is an economic  necessity in today’s golf economy.  

Pesticides 

Pesticides, insecticides, and fungicides are  commonly used on golf courses to deal with  unwanted pests. Chemical manufacturers  have modified and reformulated these  products over time to improve safety and  impact on the environment. Early products  contained high levels of arsenic, cadmium,  lead, and other heavy metals. These are now  gone and replaced with synthetic chemicals  such as organophosphates that raise new  concerns in regard to bioaccumulation and  human health.  

Excellent training and application techniques  have helped courses successfully use these  products with few major incidents. However,  mortality studies have shown an elevated  incident rate of brain, Non Hodgkins  lymphoma, prostate and large intestine  cancers in golf course superintendents who  are exposed to these chemicals (Kross, 1997). 

Not only do pesticides kill unwanted pests,  but they also negatively affect beneficial soil  microorganisms, and in doing so, halt or  decrease the amazing work these microbes do  within soils. For example, nitrogen-fixing and  phosphorus mineralizing microorganisms  have been observed to become inactive in soils contaminated with pesticides.  

Finding ways to reduce pesticides
Microbial Web in soil – Finding ways to reduce pesticides

Finding ways to reduce pesticides should be  an important initiative in golf. Courses, such  as the Vineyard Golf Club, Martha’s  Vineyard, MA and Rivermont Golf Club,  Atlanta, GA have leveraged reducing  chemical inputs into a more organic approach  to turf management. This requires a  significant change in the perspective of  golfers to accept a more natural look on the  course vs. the “Augusta Look” of deep green  and white sand bunkers over the entire  property.  

Fungi is an essential soil component that  sequesters carbon and breaks down complex  organic matter such as cellulose and lignin  (thatch control). But some species of fungi  are pathogenic and can cause plant disease in  turf. Two options to treat pathogenic disease  are to apply fungicides to kill the fungi or  promote healthier soil so that healthier fungi  can outcompete pathogenic species.  

Healthy turf can fight pathogens fairly well  by protecting the plant roots. But once the  plant becomes stressed, it’s much more  difficult to resist pests and disease. Fungal  spores can be dormant for many years in soil  and be activated by a number of factors:

  • Too much moisture.  
  • Pesticides that kill off beneficial bacteria  and fungi 
  • Lack of oxygen in the soil  

Increasing the dissolved oxygen in the  irrigation water and in the soil can reduce the  potential for pathogenic fungi to grow and  can also stimulate the beneficial microbe  community to increase dominance in the soil.  Focusing on this approach vs. applying  fungicides can stop the cycle of “treating the  symptom instead of the cause”.  

Improving soil oxygen with water

Existing cultural methods in golf to increase  soil oxygen have focused on modifying the  soil surface to introduce more air and re establish a larger pore space – literally  punching holes in the soil. Various mechanical tools are used – Air2G2, DryJect,  Hydroject, core aerification, drill and fill, etc.  

The common practice of mechanical  aerification impacts only about 10 percent of  the soil volume in exposing it to atmospheric  air after these treatments. This process  requires a significant investment in time and  money to complete and leaves putting  surfaces in poor condition while they heal –  resulting in loss of revenue for greens fees  courses and unhappy golfers.  

When discounting hydrophobic regions, water  will deliver oxygen to 100 percent of the  turf’s soil volume. This is one of the main  benefits of using water’s natural ability to  transport dissolved oxygen. Plus, by filling  both the water space and the pore space with  highly oxygenated water, the soil microbial  community benefits greatly.  

Golf superintendents haven’t focused on  enhancing the oxygen content of water  because the technology to maintain O2 in  water (especially warmer water) for extended  periods, was unavailable. Efforts to increase  irrigation DO by increasing pond aeration  have failed because the bubbles float.  

Floating bubbles, or buoyancy, is a natural  consequence of conventional aeration. When  air is mixed into a water source through a  fountain, aerator, mixer, etc. the resulting air  bubbles formed are at least 1 micron in size  and they float. The bubbles rise up into the  pond until they reach the surface, then break  open and release their cargo of oxygen back  into the atmosphere. Thus, DO increase with  these methods is limited. 

Macro, Micro and Nanobubbles
Macro, Micro and Nanobubbles

Research into making bubbles that don’t float  was started in Japan and South Korea a  number of years ago. In early experiments  these ultra fine bubbles, called nanobubbles,  were formed with pressurized dissolution,  electrolysis, or by mixing liquids in a  chamber and then feeding them through a  shear point.  

Many advances in these technologies have  resulted in a recent adoption of nanobubble  water in hydroponics and other agriculture to  improve plant oxygen. Nanobubbles are also  gaining widespread interest in improving fish  farms and for algae control in ponds and lakes. The golf industry is just beginning to  implement nanobubble technology to improve  irrigation water quality.  

The latest nanobubble oxygen technology  utilizes cavitation to shear the oxygen bubble  into a particle size of less than 200 nm  (essentially smaller than a virus and just  larger than DNA). The process works by  utilizing a sophisticated pattern of cavitation  chambers and shear planes to initiate a  controlled endothermic reaction which  produces a high concentration of oxygen  nanobubbles (over 240 million / gallon) with  a mean particle size between 50 -100 nm. A  series of partial plates is housed in a pipe that  is installed inline. The plates are oriented in a way that  forces  flowing  water to  expand and  contract  under shear  stress many  times while  flowing through the pipe.  

Nanobubble Generator – series of partial plates

The expansion and contraction in the  nanobubble processor creates cavitation,  which is the formation of gas bubbles within  a liquid due to rapid pressure changes. The  processor is designed in a way that the voids  are small enough to form nanobubbles, and  shift the zeta potential of the particles in the  water toward zero or negative.  

Because cavitation operates at low pressure,  oxygen nanobubbles tend to stay in solution  much longer than conventional aeration. This  allows oxygen to be deposited on the bottom  of lakes and ponds where it can transform the  bottom muck into an aerobic environment and  consume nutrients – curtailing algae  production. Irrigation water can hold oxygen  longer and transport it to the root zone and to  the plant roots at levels of 18-30 ppm of DO –  nearly 2-3 times higher than rainwater.  

Another key feature of nanobubble oxygen is  the large surface area (because of the tiny  bubble size) and the highly negative charge  each bubble has.  

negative charge improving retention in the soil
negative charge improving retention in the soil

This negative charge is responsible for  improving cation retention in the soil  (increasing CEC  for calcium for  instance) and for reducing the  surface tension  on the soil  surface.  

Because of the  protective action  of soil microbes to generate a polysaccharide  “slime” layer around them and increase  surface tension and contact angle, hydrophobic areas can develop in stressed  soil. Those areas are not wettable and can become oxygen deficient. If water is not able  to adequately penetrate the depths of a 2-inch  to 8- inch root zone, soil gases are trapped as  well and oxygen deficiencies emerge.  

Wetting agents / surfactants can be used in  treating hydrophobic areas and returning  moisture to sections of the green that are dry.  They also transport oxygen dissolved in water to the turf root zone (Roberts, 2002). But they  are expensive and subject to overuse. Instead,  by utilizing nanobubble oxygen water, the  highly negative charge of the oxygen bubbles  and extremely high surface area virtually  eliminate the  need for these  expensive  wetting agents  – resulting in a  much more  sustainable  and consistent  infiltration rate.  

Nanobubble infiltration testing
Nanobubble infiltration testing

Injecting  ozone ahead of  the cavitation  unit creates ozone nanobubbles that can  oxidize biofilm and organic material  throughout the irrigation system. Cleaner  pipes and sprinkler heads help maintain a  higher DO level as well as decreasing the  spread of disease in the turfgrass and reducing  maintenance requirements of irrigation  systems. Ozone is also effective in killing  spores and molds in irrigation water, further  reducing pathogens (Warwick, Avondale Golf  Club, Sydney).  

Continuing research  

Research in Australia has been conducted on  both Couch grass (warm season) and Rye grass (cool season). This work, by P.  McMaugh, has shown that cool season  grasses treated with high DO nanobubble  water are able to better handle the stress of  infrequent watering in hot conditions. Also,  root loss was markedly less in turf treated  with high DO water – in fact, cool season grass root mass increased in hot conditions,  even when the turf was under stress.  

Related: Australian Golf Courses Recognized in Global List

Water infiltration testing in Australia, where  there are now three golf courses using  nanobubble oxygen water full time to  improve irrigation water quality, has shown a  dramatic increase without using wetting  agents. These same golf courses have  documented 50+% reductions in fungicide  and fertilizer while using nanobubble oxygen  and ozone in their irrigation water. 

Warm season grasses also benefit from  nanobubble oxygen water with significantly  less stress and better root mass with higher  DO water. Manly Golf Club, Sydney, has confirmed better root mass development and  reduced fungicide and fertilizer use with  nanobubble oxygen irrigation water. Avondale Golf Club, Sydney, has significantly  increased water quality and plant disease in  bent grass by incorporating both nanobubble  oxygen and ozone in their treatment system.  

The University of Arkansas (Richardson, De Boer) has documented increased turf DGCI  (Dark Green Color Index) levels on bent grass  using nanobubble oxygen water. This  research was conducted using membrane generated nanobubble oxygen water. Higher  nanobubble generation rates of cavitation  technology would yield additional bent grass  benefits in terms of root mass increase as  previously shown by McMaugh’s work.  

The University of Georgia is using cavitation  to generate nanobubble oxygen water for  testing on warm season turf growth rates, root  mass development, color, nutrient uptake,  water infiltration rate and pathology. An 18%  reduction in dollar spot was observed. UGA is  also studying the impact of displacing salts in  the soil profile caused by improved  infiltration. M. Hoban (Rivermont GC) has reported improved color response in field  plots irrigated with nanobubble oxygen water  and tested by UGA.  

REFERENCES  

  • Barton, John. (March 2008). “Golf and the Environment”. Golf Digest. 
  • Berndt, Lee, Joe Vargas Jr., and Brad Melvin, (March 1989). “Sulfur,  Organic Matter And the Black Layer.” Golf Course Management, p 48.  
  • Horgan, Brian. (March 2003) “Denitrification Impedes Fertilizer  Effectiveness.” Turfgrass Trends, p 52-57.  
  • Kross, BC, (May 1996) “Proportionate Mortality Study of Golf Course Superintendents”. American Journal of Medicine. P 501 
  • Lyman, Gregory T. (November 2012). “Golf’s Use of Water: Challenges  and Opportunities. USGA Summit on Golf Course Water Use” 
  • Morgan, Lynette PhD. (May/June 2000). “Are Your 
  • Plants Suffocating? The importance of Oxygen in Hydroponics.”  Practical Hydroponics & Greenhouses, p 52.  
  • Roberts, Eliot C. PhD. (April 1990) “Soil / Air / Water Plant  Relationships.” Landscape & Irrigation, pp 72-76.  
  • Simojoki, Asko. (2001) “Oxygen Supply to Plant Roots in Cultivated  Mineral Soils.” Department of Applied Chemistry and Microbiology,  University of Helsinki.  
  • Smart, Bud. PhD. (Jan/Feb 1999) “Maintain the Best Irrigation Water  Quality on the Golf Course.” USGA Green Section Record, p1  
  • Tredwell, Lane, PhD,Stowell, Larry PhD, Gelenter, Wendy PhD , (November 2006) “Yellow Spot and the Potential Role of Cyanobacteria  as Turfgrass Pathogens”. GCM p83 
Warwick, David. May 2018. Nanobubble Technologies and Avondale  Golf Club. YouTube.

Ron Pote is owner of Byo-Gon, Inc. and NanoOxygen Systems an  environmental company based in Charleston, SC. His passion for  golf is a big part of his efforts to improve the environmental footprint  of the game. 

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