Slide 1
LHAP 106 - Compaction and Thatch Management
Powerpoint built by School of Environment Staff, adapted by E. Wheale
Period 1
Compaction & Thatch 1 hr (1)
Printable reference generated from local Period 1 material.
Extracted Text and Images
Extracted locally from the source file.
Slide 1
LHAP 106 - Compaction and Thatch Management
Powerpoint built by School of Environment Staff, adapted by E. Wheale
Slide 2
Compaction is: The pressing together of soil particles into a more dense mass by various physical forces.
What are the EFFECTS of Soil compaction on plants?
Soil Compaction
Slide 3
Effects of Compaction:
Reduction of Pore Space**
MICROPORES:
less water infiltrates (drying), what is absorbed doesn’t drain (swampy conditions).
Pooling and runoff are increased
MACROPORES:
diffusion of oxygen is limited
ventilation of gases is reduced (toxicities)
usda.com
usda.com
Slide 4
One of the most serious problems in turfgrass management
Shows up as
poor vegetation health
standing water
bare ground
Poa annua invasion
SYMPTOMS OF COMPACTION
Slide 5
So. What factors lead to Soil Compaction?
What increases the potential & what is the actual cause?
Slide 6
Potential for compaction: Soil Type
Sandy soils
gustinceramics.com
Fine Textured (clay, silt)
VS
Slide 7
Potential for compaction:
Shoot Density & Soil Moisture
Higher shoot density resists compaction
Appropriate thatch layer helps to resist compaction
Water acts as a lubricant and will accelerate compaction.
Moist soils are the most prone (not wet soils)
Slide 8
Dynamic force
Heel and toe more stressful than the arch or ball of the foot
2-4 passes with Machinery may reach 90% of maximum compaction
Uniformity and distribution of pressure are key factors
Causes of Compaction - External Pressure
Slide 9
Compaction Comparisons
exponent.com
Hovercraft: 0.7 kPa (0.1 psi)
Human on Snowshoes: 3.5 kPa (0.5 psi)
Rubber-tracked ATV: 5.165 kPa (0.75 psi)
Human Male (1.8 meter tall, medium build): 55 kPa (8 psi)
M1 Abrams tank: 103 kPa (15 psi)
1993 Toyota 4Runner / Hilux Surf: 170 kPa (25 psi)
Adult horse (550 kg, 1250 lb): 170 kPa (25 psi)
Passenger car: 205 kPa (30 psi)
Wheeled ATV: 240 kPa (35 psi)
Mountain bicycle: 245 kPa (40 psi)
Racing bicycle: 620 kPa (90 psi)
Note pressures for Man and Horse are for standing still. A walking human will exert more than double its standing pressure. A galloping horse will exert up to 3.5 MPa (500 psi)
Slide 10
Mowing Pattern
arkansasagnews.uark.edu
Slide 11
Severity of Soil Compaction?
top 3 cm of the rootzone is most affected
can affect roots to a depth of 7.5cm and extend as deep as 40 cm.
Slide 12
How is Compaction Alleviated?
Preventative Viewpoint
Minimize the factors that affect the potential for compaction (ie. soil type, tracks, turf tires)
Control and minimize the intensity of use
Proper design and plantings critical.
Offer large number of varying routes.
Careful placement of walks and cart path, rotating goal posts
The Turfgrass Manager Must cooperate in the design process so that the requirements of load bearing AND those of plant growth are met
Slide 13
How is Compaction Alleviated?
Remedial Viewpoint
Assumes that compaction is always going to be a problem.
How best is the issue to be dealt with?
Aeration or Rototilling
Often the remediations serve double duty as a mitigation for Thatch.
Slide 14
Thatch Management
Presentation developed by school of Environment staff. Adapted by E. Wheale
Slide 15
WHAT IS THATCH?
Layer of dead and decaying (living) tissue located between the green vegetation and the soil surface
Thatch comprises the upper stratum of the medium that supports turfgrass growth
Newly added materials may be largely undecomposed towards the top
Materials at the bottom in contact with the soil are at a more advanced stage of decomposition
What IS Thatch?
Slide 16
WHAT IS THATCH?
When integrated with the soil surface it forms a thatchlike derivative called ‘mat’.
Mat can provide surface resiliency and stabilize turf against impact
Are there any Benefits to Thatch?
Slide 17
BENEFITS OF THATCH
Increased wear tolerance
Aids in resiliency / moderates soil temperature
Reduces compaction potential
17% less G-force on falling athlete due to thatch cushion (Brede, 2000)
Absorbs and degrades pesticides (Brede, 2000)
Reduces water loss from soil
Reduces weed seed germination
Death of the turfgrass community often follows
the destruction of the thatch layer
Benefits to Thatch
Slide 18
CAUSES OF THATCH
Thatch develops when rate of accumulation exceeds rate of decomposition
Any factor that stimulates shoot growth will increase accumulation of organic matter
Any factor that reduces microbial activity in the soil will impair the decomposition process
Slide 19
HOW MUCH THATCH IS GOOD?
Rule of Thumb:
Half the mowing height
Slide 20
Thatch accumulation in Clay and Sandy soils...
Slide 21
Slide 22
Problems with Thatch - above
Roots grow into Thatch
warmer, wetter, fertilizer catchment
Growing points above protective soil zone
Crowns vulnerable to scalping and temperatures
Plants are easily pulled by hand
Lawn puffiness and scalping
Often misdiagnosed as dull mowers
Prone to desiccation
Requires excessive management
Thatch Problems - Above Ground:
Slide 23
Rooting in Thatch
Above: root system and crown easily compromised
Vs Beside: roots and rhizomes growing in soil layer.
Slide 24
Slide 25
DAMAGE FROM THATCH
Slide 26
THATCH
Slide 27
CONTROLLING THATCH
THATCH
Slide 28
Problems with Thatch
within & below
Increased disease and insect problems
Insects live and feed in the thatch
sod webworms, white grubs
Disease organisms are harboured in this layer
Dollar spot, fairy ring
Impact of fungicides and pesticides reduced
Dry Soil Conditions
Slide 29
THATCH DAMAGE
Slide 30
CONTROLLING THATCH
CONTROL OF THATCH - Cultural
Slide 31
CONTROL OF THATCH
Cultural - Preventative Approach
Use management practices that encourage decomposition and avoid excess shoot growth
Aeration and compaction prevention
Top-dressing
(adds Micro-organisms: thatch sandwich!)
Depends on how fast it is forming - use a 1.6 mm depth weekly to start
Use appropriate mowing frequencies and height
Minimize pesticides
Moisture - keep it watered, and water deeply to encourage roots
Slide 32
Case Study:
Thatch buildup on residential lawn
Customer called regarding very large dead spots in the lawn, some are half circles (looks like fairy ring but it is dead patches)
Lawn feels spongy underfoot
Many flies / bugs visible crawling on top of the thatchy dead sections.
What should you suggest?
Slide 33
Slide 34
Extracted Slide Text and Images
Text and media extracted locally from the presentation.
Slide 2
Compaction is: The pressing together of soil particles into a more dense mass by various physical forces.
What are the EFFECTS of Soil compaction on plants?
Soil Compaction
Speaker Notes
- One of the most serious problems facing turfgrass managers
- Not simple, can have harsh consequence; difficult to prevent, serious cost implications
- Definition – the pressing together of soil particles into a more dense mass by physical forces
Slide 3
Effects of Compaction:
Reduction of Pore Space**
MICROPORES:
less water infiltrates (drying), what is absorbed doesn’t drain (swampy conditions).
Pooling and runoff are increased
MACROPORES:
diffusion of oxygen is limited
ventilation of gases is reduced (toxicities)
usda.com
usda.com
Speaker Notes
- One of the most serious problems facing turfgrass managers
- Not simple, can have harsh consequence; difficult to prevent, serious cost implications
- Definition – the pressing together of soil particles into a more dense mass by physical forces
Slide 4
One of the most serious problems in turfgrass management
Shows up as
poor vegetation health
standing water
bare ground
Poa annua invasion
SYMPTOMS OF COMPACTION
Speaker Notes
- Poor vegetation health – may see damage to the crown and leaf blades; poor looking turf is an early symptom of compaction; often used to diagnose the problem before it becomes severe and requires major renovations
- May see standing water (ie. Right after rain, after irrigation); compaction reduces water infiltration rates resulting in standing water
- Reduced root and shoot growth; reduced water and nutrient uptake, reduced tolerance to heat and drought stresses, increased susceptibility to scald and direct low-temperature injury.
- Bare ground – seen on footpaths or tire tracks or traffic routes; created by intense use in concentrated areas; foot and vehicular traffic are the most common causes; turf has died out leaving exposed ground
- Ecological responses – shifts to compaction-tolerant weed populations such as knotweed (frequently occurs where severe soil compaction limits turfgrass growth), annual bluegrass, goosegrass, white clover
- More frequent fertilization and irrigation required to compensate for restricted rooting and generally poor growth.
- Poa annua – apple green grass, spreads via seeds; tolerates low mowing heights and heavily compacted soil, zero fertility, still produces lots of seeds thereby perpetuating itself; has trouble on porous, well drained soils, can’t compete with KB and CRF
- In compacted situations Poa becomes more competitive and fills in as other grasses die out.
Slide 5
So. What factors lead to Soil Compaction?
What increases the potential & what is the actual cause?
Slide 6
Potential for compaction: Soil Type
Sandy soils
gustinceramics.com
Fine Textured (clay, silt)
VS
Speaker Notes
- Fine Textured: water from pore spaces get discharged, expulsed when COMPACTED
- Sandy Soils:
- particles are not compressible
- have little to no structure development
- usually single-grained
- particles just get reoriented but don’t lose pore space - This is why extremely heavy traffic areas like golf and bowling greens, high end athletic fields – constructed using a sand based media mix – don’t compact as quickly
Slide 7
Potential for compaction:
Shoot Density & Soil Moisture
Higher shoot density resists compaction
Appropriate thatch layer helps to resist compaction
Water acts as a lubricant and will accelerate compaction.
Moist soils are the most prone (not wet soils)
Speaker Notes
- Why do we cut grass so short? (public perception of playing fields and golf greens - manicured grass takes a LOT of input b/c it’s so unnatural)
- Amount of vegetation – taller cutting heights mean more vegetation for cushioning; higher shoot density resists compaction; thick thatch layer
- **cutting height, shoot density, thatch layers
- Avoid irrigation during high traffic times.
Slide 8
Dynamic force
Heel and toe more stressful than the arch or ball of the foot
2-4 passes with Machinery may reach 90% of maximum compaction
Uniformity and distribution of pressure are key factors
Causes of Compaction - External Pressure
Speaker Notes
- Compaction – primarily because of traffic – foot and vehicular
- Foot traffic – the greater the intensity the greater the degree and depth of soil compaction
- Frequency – how often – ie kids playing soccer 5 nights per week will do more damage that adults playing occassional games of football
- Options for mitigating goal-box damage?
- Sand bases with sub drainage
- Rotation of goal posts / field orientation.
- Discuss “leave no trace”
Slide 9
Compaction Comparisons
exponent.com
Hovercraft: 0.7 kPa (0.1 psi)
Human on Snowshoes: 3.5 kPa (0.5 psi)
Rubber-tracked ATV: 5.165 kPa (0.75 psi)
Human Male (1.8 meter tall, medium build): 55 kPa (8 psi)
M1 Abrams tank: 103 kPa (15 psi)
1993 Toyota 4Runner / Hilux Surf: 170 kPa (25 psi)
Adult horse (550 kg, 1250 lb): 170 kPa (25 psi)
Passenger car: 205 kPa (30 psi)
Wheeled ATV: 240 kPa (35 psi)
Mountain bicycle: 245 kPa (40 psi)
Racing bicycle: 620 kPa (90 psi)
Note pressures for Man and Horse are for standing still. A walking human will exert more than double its standing pressure. A galloping horse will exert up to 3.5 MPa (500 psi)
Speaker Notes
- Interesting – but it still depends on frequency…
- Imagine a polo field!! (Man 9 psi Running Man 18 psi vs TANK 15 psi, running Horse… 500 PSI!) Putting tracks on a skidsteer vs tires can make a huge difference.
Slide 10
Mowing Pattern
arkansasagnews.uark.edu
Speaker Notes
- Lawn mower IS just a small vehicle - or a push mower with the foot traffic… also think about the continual pounding of irrigation water…
- blended with salts/micro-nuts (we know Mg and Ca add to compaction) added our uber-dethatched lawns with no clippings and constant mowing...
Slide 11
Severity of Soil Compaction?
top 3 cm of the rootzone is most affected
can affect roots to a depth of 7.5cm and extend as deep as 40 cm.
Speaker Notes
- Depends on:
- soil texture & structure, organic matter content, soil moisture at the time of compaction
- Soil compaction can occur in different zones within the soil. In turf grasses, the most common soil compaction situations would be:
- In the first few centimeters of the soil surface
- Surface compaction but to a depth of 20 to 40 cm
- Deep in the soil profile in either a narrow or wide zone
- Each of these circumstances would result in different effects on air, water, and root movement, as well as presenting unique management or correctional problems.
- Beard (1973) noted that a majority of compaction in turfgrass situations occurred in the top 8 cm of soil surface, mostly in the upper 3 cm.
- Sills and Carrow (1982) and O' Neil and Carrow (1982) found that the soil bulk densities were influenced mainly in the upper 3 cm.
- This type of compaction is the easiest to correct because cultivation equipment can penetrate this surface zone.
- Sometimes a compacted zone can occur below the surface. For example, in housing developments the original topsoil may be stripped, construction equipment run on the subsurface, and then 8 to 20 cm of topsoil is applied on a top of the compacted subsoil. It is also the most difficult soil compaction to correct
Slide 12
How is Compaction Alleviated?
Preventative Viewpoint
Minimize the factors that affect the potential for compaction (ie. soil type, tracks, turf tires)
Control and minimize the intensity of use
Proper design and plantings critical.
Offer large number of varying routes.
Careful placement of walks and cart path, rotating goal posts
The Turfgrass Manager Must cooperate in the design process so that the requirements of load bearing AND those of plant growth are met
Speaker Notes
- Two viewpoints - prevention (ideal) and remediation
- Prevent traffic from building up…how might we do that on campus?
- Guide and control traffic through the proper selection and placement of trees, shrubs, walks, roadways, contours.
- Design should offer as large a number of alternate routes from one location to another
- Look for wear where people take short cuts – consider redirecting back onto a pathway
- Place pathways so that they follow the most natural or closest route between destinations
- So what do we do when we can’t be a part of it? sometimes we need to do some later installation:
- put in turf-stone perhaps or a walkway or garden to stop people from walking. It’s pretty tough to do much when the subsurface has been compacted heavily…
- Install subsurface drainage (herringbone pattern) to a pool
- consider turfstone or plastic grid sod pavers.
Slide 13
How is Compaction Alleviated?
Remedial Viewpoint
Assumes that compaction is always going to be a problem.
How best is the issue to be dealt with?
Aeration or Rototilling
Often the remediations serve double duty as a mitigation for Thatch.
Slide 14
Thatch Management
Presentation developed by school of Environment staff. Adapted by E. Wheale
Slide 15
WHAT IS THATCH?
Layer of dead and decaying (living) tissue located between the green vegetation and the soil surface
Thatch comprises the upper stratum of the medium that supports turfgrass growth
Newly added materials may be largely undecomposed towards the top
Materials at the bottom in contact with the soil are at a more advanced stage of decomposition
What IS Thatch?
Speaker Notes
- The undecomposed or partially decomposed layer of organic matter above the soil surface (and constituting the upper stratum of the medium that supports turfgrass growth) There are many misconceptions about thatch. Thatch is a tightly intermingled organic layer of dead and living shoots, stems, and roots that accumulate just above the soil surface. Nodes of stems and crown tissues are the most resistant to decay, so compose the largest component of thatch. High lignin content found in cell walls also contributes (Creeping Red Fescue).
- Lignin - found especially in woody species, is the schlerinkema cells that provide stability
- It is not the leaf clippings left over after mowing or those that find their way to the soil surface. Looks a dull brown colour and appears to be mostly dead material
- Caused by earthworm action, wind, topdressing, core aeration
- Thatch includes the growth of adventitious roots and stolons above the soil surface and provides a catchment. Materials decompose more slowly than if they were in the soil. Look out for Kentucky Bluegrass (rhizomes), Creeping red fescue (rhizomes, lignin), Creeping Bentgrass (stolons and grain) and/or Quackgrass…
- gH media review – it is well-aerated, compaction-resistant with poor nutrient and water holding properties. Turfgrasses with most of their roots confined to the thatch layer are more prone to injury from environmental stress.
Slide 16
WHAT IS THATCH?
When integrated with the soil surface it forms a thatchlike derivative called ‘mat’.
Mat can provide surface resiliency and stabilize turf against impact
Are there any Benefits to Thatch?
Speaker Notes
- Mat IS good thatch. We like mat.
- A block of turf may contain one or more of these features (thatch, mat, soil) depending on naturally occurring phenomena, cultural practices and turfgrass genotypes.
Slide 17
BENEFITS OF THATCH
Increased wear tolerance
Aids in resiliency / moderates soil temperature
Reduces compaction potential
17% less G-force on falling athlete due to thatch cushion (Brede, 2000)
Absorbs and degrades pesticides (Brede, 2000)
Reduces water loss from soil
Reduces weed seed germination
Death of the turfgrass community often follows
the destruction of the thatch layer
Benefits to Thatch
Speaker Notes
- Advantages – helps improve wear tolerance by protecting the crowns of plants; buffer between compactive forces and the soil surface; insulates soil against temperature extremes
- Doug Brede in his book, Turfgrass Maintenance Reduction Handbook: Sports, lawns, and Golf. C 2000 by sleeping bear press. Chelsea, MI.
- https://books.google.ca/books?id=eJgaza9GmHEC&pg=PA184&lpg=PA184&dq=turfgrass+-+high+lignin&source=bl&ots=R6KauvVbvA&sig=KePzK75ek5U9wGJz5cucZOfIgLk&hl=en&sa=X&ved=0ahUKEwjR9PXAqLHJAhUQWYgKHVCaCr0Q6AEIMjAC#v=onepage&q=turfgrass%20-%20high%20lignin&f=false
- Page 187
- “1. Thatch absorbs and degrades pesticides and fertilizers
- a study led by Charles Mancino (Manicno et al., 1993) found that thatch contained 40 - 1600 times as many bacteria 500-600 times as many fungi, and up to 100 times as many actinomycetes organisms as soil; these microorganisms are vital in pesticide decay.
- Water leaching out of thatch layer can meet or exceed drinking water standards for purity, due to the water purifying properties of thatch and its cadre of microbes (Watschke, 1991)
- NOTE - Thatch also adds a significant amount of organic matter and Mineral (via clippings) to the soil. Make sure your amendments are necessary.
Slide 18
CAUSES OF THATCH
Thatch develops when rate of accumulation exceeds rate of decomposition
Any factor that stimulates shoot growth will increase accumulation of organic matter
Any factor that reduces microbial activity in the soil will impair the decomposition process
Speaker Notes
- Thatch develops when rate of accumulation exceeds the rate of decomposition.
- Any cultural (Excessive N or irrigation) or environmental factor (Ideal growing) that stimulates excessive shoot growth will increase the accumulation of organic material that needs to be broken down. Related to mowing height: as the height lowers, other maintenance such as irrigation and fert increase;
- Any cultural or environmental factor that reduces microbial activity in the soil will impair the decomposition process and lead to more thatch (Compaction, flooding, hydrophobic conditions, use of pesticides)
- Accumulation of clippings is ONLY a problem in high-lignin species that are not subject to proper mowing practices. (thereby the stems may contribute.) This is NOT considered to be a true contributer.
Slide 19
HOW MUCH THATCH IS GOOD?
Rule of Thumb:
Half the mowing height
Speaker Notes
- According to Doug Brede in his book, Turfgrass Maintnenance Reduction Handbook: Sports, lawns, and Golf, https://books.google.ca/books?id=eJgaza9GmHEC&pg=PA184&lpg=PA184&dq=turfgrass+-+high+lignin&source=bl&ots=R6KauvVbvA&sig=KePzK75ek5U9wGJz5cucZOfIgLk&hl=en&sa=X&ved=0ahUKEwjR9PXAqLHJAhUQWYgKHVCaCr0Q6AEIMjAC#v=onepage&q=turfgrass%20-%20high%20lignin&f=false
- The acceptable range is 12mm - 25mm - any less will not cushion. any more will have negative effects.
- Influenced by Tolerances – thin layer of no more than 6-8mm on bentgrass on golf course or lawn bowling where uniformity is key.
- Under high maintenance conditions, turf manager would incorporate regular dethatching (power raking, vertical mowing) as part of the maintenance program just to keep a thinner thatch layer. (ie. Bentgrass – grooming heads daily, verticut heads biweekly or monthly
- On low maintenance areas, usually use a higher cutting height, less frequent mowings; this allows for a greater thickness of thatch – also less water, less fertility, so lower growth rate, slower thatch building, thicker thatch layer is tolerated.
Slide 20
Thatch accumulation in Clay and Sandy soils...
Speaker Notes
- On the left, the soil is super compacted - the thatch layer (such as it is) is what’s keeping it looking half decent.
- On the right, the thatch is probably a bit extreme… probably a candidate for coring.
Slide 21
Speaker Notes
- Note - very low (almost no) thatch in this residential soil. High mowing height = high sheath. A sudden low shear WILL contribute to thatch because the clippings are high lignin. It will also stress the grass.
Slide 22
Problems with Thatch - above
Roots grow into Thatch
warmer, wetter, fertilizer catchment
Growing points above protective soil zone
Crowns vulnerable to scalping and temperatures
Plants are easily pulled by hand
Lawn puffiness and scalping
Often misdiagnosed as dull mowers
Prone to desiccation
Requires excessive management
Thatch Problems - Above Ground:
Speaker Notes
- Rooting in thatch instead of into the mineral soil; (thatch is warmer, wetter, gets fert first) - can easily be pulled up by hand or maintenance machinery.
- crowns become elevated (draw diagram - differentiates at a higher point in the profile and pushes the plant upwards) growing points are exposed; turfgrass plant start to root in the thatch layer ; can be easily pulled out by hand; this is also easily scalped - the complete removal of plant canopy, cutting into the crown and causing death.
- Lawn puffiness and scalping may be diagnosed as duller mowers or user error rather than excessive thatch
- bad thatch levels in home lawns is it doesn’t hold much water, the turf roots becomes susceptible to drought damage even under mild water stress.
- Results in weakened, poorly rooted turf that is prone to stress injury - increasing management needs.
Slide 23
Rooting in Thatch
Above: root system and crown easily compromised
Vs Beside: roots and rhizomes growing in soil layer.
Speaker Notes
- Easy it would be to pull that up when there are almost NO roots down into the soil.
- It’s also easy to start to imagine the nutrition in there - how it can dry out or be depleted… especially b/c we know that the process of decomposing USES nitrogen. (lignin is high carbon)
Slide 24
Speaker Notes
- Photo Credit - I. Morrow, Olds college
- No roots below, can grab and pull like a rug
- Very poor thatch : mowing height ratio!!! (look at turf height vs thatch depth)
- Note the dessicated sections - what does that look like?
- Compaction?
- Phosphorus? poor rooting
- You won’t know until you try a core.
Slide 25
DAMAGE FROM THATCH
Speaker Notes
- mowers ripping up turf, scalp the crown, result is stressed plants...
Slide 26
THATCH
Speaker Notes
- Scalping:
- Mowing heights are set on hard surface.
- Set mower down onto spongy turf and it sinks and scalps - and bounces…
Slide 27
CONTROLLING THATCH
THATCH
Speaker Notes
- Next 7 photos - I. Morrow, olds college (dominican republic)
- Spongy turf
Slide 28
Problems with Thatch
within & below
Increased disease and insect problems
Insects live and feed in the thatch
sod webworms, white grubs
Disease organisms are harboured in this layer
Dollar spot, fairy ring
Impact of fungicides and pesticides reduced
Dry Soil Conditions
Speaker Notes
- Disadvantages (esp. if thatch too thick) – increased disease and insect problems;
- Environment good for disease causing organisms ideal food supply and habitat for turf feeding insects (dollar spot, fairy ring, sod webworm, white grubs);
- Effect of fungicides and insecticides (cannot penetrate to where it is most needed (ie. on the insect or disease spores and fungi); pesticides end up in the thatch layer not on the pest itself
- Hygroscopic conditions differ from desiccation as stated previously –
- Thatch dries out and does not allow water to penetrate through to the soil
- When thatch completely dry it stretches the water tension into a water repelling layer
- Water cannot infiltrate
- See irregular spots of wilting turf that turns brown
- manifests as premature summer dormancy while other parts of the turf are healthy
Slide 29
THATCH DAMAGE
Speaker Notes
- Photo Credit - I. Morrow Olds College - dominican republic
- Warm Season Grass - Huge insect burrows into the sand beneath the grass
- insecticide use kills Micro organisms that destroy thatch
- Bugs not getting hit because of the thatch (and improper application methods)
Slide 30
CONTROLLING THATCH
CONTROL OF THATCH - Cultural
Speaker Notes
- Photo credit: I Morrow - Olds college (dominican republic)
- aeration isn’t always the answer… it pulled the turf off the green! Pull it all off, reseed, wait til it’s impossible and then re-do the cycle.
- Instead, problem solve and make a change!!
Slide 31
CONTROL OF THATCH
Cultural - Preventative Approach
Use management practices that encourage decomposition and avoid excess shoot growth
Aeration and compaction prevention
Top-dressing
(adds Micro-organisms: thatch sandwich!)
Depends on how fast it is forming - use a 1.6 mm depth weekly to start
Use appropriate mowing frequencies and height
Minimize pesticides
Moisture - keep it watered, and water deeply to encourage roots
Speaker Notes
- Control methods:
- “Cultural” controls: practices that you have that will prevent problems. “Biological”:utilizing natural combatants (like ladybugs for aphids). “Mechanical” will use physical tools. “Chemical” - self explanatory.
- Culturally, we are using our management practices rather than a reactive curative approach. We want to stimulate thatch decomposition rates and avoid excessive stimulation of shoot growth (hills and valleys).
- Aeration - benefits of aerating for compaction is that thatch is naturally controlled.
- Topdressing generally more effective than aeration or vertical mowing - adds a layer of MicroOrganisms that break down from above -
- Make SURE to match your soil types - no fine silts over heavy clay loam or mineral soils over sand… layering problems leading to perched water tables.
- Things that help the decomp rate: Carbon to N ratio - 25:1 or 30:1, optimum for decomp. Dead organic material is high in C, fresh clippings are high in N. If the balance isn’t right, decomposition will slow.
- Soil - thatch builds up more on poorly drained, fine textured soils (as opposed to well aerated, coarse textured).
- MO work best at 10-18 C and pH 6.5-7.5
Slide 32
Case Study:
Thatch buildup on residential lawn
Customer called regarding very large dead spots in the lawn, some are half circles (looks like fairy ring but it is dead patches)
Lawn feels spongy underfoot
Many flies / bugs visible crawling on top of the thatchy dead sections.
What should you suggest?
Speaker Notes
- A very rare case - the customer irrigates and fertilizes heavily.
- mowing frequency is unknown (suspected weekly), clipping handling is unknown.
- Lawn is south facing on an extreme slope (33% or near to it in places). It is a large acreage (at least 1.5 acres of lawn) - it has never been power raked, only spot aerated once in 10 years.
- Suspicion is that its many problems combining to create this: Mower scalps / slides on the edges of the steepest sections. The turf is rooting into the thatch and drying because the irrigation water runs off. Insect life accumulates in this thatch layer. Between insects, mechanical damage and drying, the dead patches are presenting.
Slide 33
Slide 34
Speaker Notes
- e kawahara 2024 - sod in June (thatch is just ONE problem)
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