selecting sand-dominated rootzones for sports … sand-dominated rootzones for sports fields tom...
TRANSCRIPT
Why Sand?
• Low nutrient retention
(Cation Exchange Capacity) • Must fertilize more often
• Must fight against organic matter accumulation • Must aerify and topdress with sand often
• No soil structure
• Expensive
Porosity
• Clay – 75% pores, 25% solid
– 65% micropores
– 10% macropores
• Silt – 50% pores, 50% solid
• Sand – 35% pores, 65% solid
– 10% micropores
– 25% macropores
Why Sand ?
Even after maximum compaction, sand still retains “ideal” pore distribution and therefore continues to drain and retain airspace
Bulk Density
• Under normal conditions, sand has a higher bulk density than clay
• Clay = many pores
• Bulk density affected by compaction
Amending a soil
• When amending a high clay soil
– Need a lot of sand (> 60%)
• When amending a high sand soil
– Need only a little clay
Will turf growing on sand wear better than turf growing on soil?
• Components of wear
– Compaction
– Abrasion
– Divoting
USGA: 35-55%
USGA: 15-30%
USGA: 15-25% You want a good balance between air-filled and capillary porosity
USGA: min. 6 in/hr
Total Porosity – Sand Effects
• Average sand size increases = T.P. decreases
• Uniformity of sand increases = T.P. increases
• Sand get rounder = T.P. decreases
• **total porosity only tells part of the story
Calcareous Sands
• Quartz (Silica) sand is best – hard and durable
• Calcareous Sand (calcium carbonates) – Physically breaks down – High pH – High particle density – Calcium Carbonate Equivalent
• < 3% - OK • 3 - 9% - High • > 9% - Problem
– Color?
Sand and Gravel Matching
• Bridging: Will sand migrate into gravel?
– Will you need an intermediate layer?
– Largest 15% of rootzone
– Smallest 15% of gravel
• Use wet sand as first layers on top of gravel
Sand and Gravel Matching
• Permeability: Will there be clogging at the interface?
– Smallest 15% of rootzone
– Smallest 15% of gravel
D15 (gravel) ≥ 5 x D15 (rootzone)
Sand and Gravel Matching
• Gravel Uniformity: Is the gravel uniform enough?
– Largest 10% of gravel
– Smallest 15% of gravel
The Quality Control Program
• Make sure you get what you are paying for
• Work with a soil testing lab experienced with sand-based athletic fields
• Small jobs – the soil test lab may be able to supply the soil specifications
• Large jobs - architect
The Quality Control Program
• Get soil suppliers to submit either blends of individual components
• Lab will test blends to see if they meet spec or will construct blends in lab to determine appropriate ratio
• Once approved by the lab, the soil supplier will be allowed to bid the job
The Quality Control Program
• One of the bidders is awarded the job
• Company makes small batches to be tested. These are called calibration runs
• After the lab has the blenders “dialed in” , a benchmark mix is established
The Quality Control Program
• Confidence intervals are established
• All soil testing up to this point is borne by the soil supplier
The Quality Control Program
• Now begins the quality control phase
• QC tests done every 500 tons mixed at the blending site
– Dig into pile with shovel
– use 4 ft long, 2 inch PVC pipe, cap one end, drive into pile
– Put in bucket and repeat 6 times
– Put on tarp and “quarter” until fill gallon ziplock
The Quality Control Program
• Send someone to check a few piles
• Explain you will be spot checking when the mix arrives as well
• Pay someone to take a small sample of every truck load that arrives. Label it and save it if questions arise later
What does 80-20 mix mean?
• 80% sand, 20% organic matter
• By volume
• 80-20 mix is usually about 0.7% OM by weight
Organic Matter
• Increased moisture retention
• Reduce bulk density
• Buffer capacity
• Increase cation exchange capacity
• Microbial activity
Peat
• Reed Sedge
– North Dakota / Minnesota
– Age: Old
– Stable
– Fine texture
• Sphagnum
– Canada
– Age: Young
– Fibrous
– High OM content
– High water holding
– Lower pH
Organic Matter
• OM should only ever be added at construction
• K. bluegrass deposits 5,000 lbs. of oven dry OM per acre per year
Organic Matter
Topsoil
• “Friend”
• > 3% OM = adequate
• > 4% OM = Good
• > 5% OM = Superior
Sand Rootzone
• “Enemy” (over time)
• > 3% (by wt.) = concerned
• > 4% (by wt.) = may see problems (poor drainage, shallow rooting, divoting)
• > 5% (by wt.) = problems typically evident
What to look for in a soil test report
• Sieve Analysis
– Breakdown of sand sizes
– Does it meet spec?
– Anything that jumps out?
What to look for in a soil test report
• Acid Reaction
– Is it calcareous?
• Shape
– Angularity and sphericity
• D15 and D85
– Used for bridging with gravel
What to look for in a soil test report
• Bulk density
– Indicator of compaction and hardness
– Used to calculate porosities
• Total porosity
– USGA: 35 – 55%
What to look for in a soil test report
• Air-filled porosity (Macroporosity)
– What % of the pores are airfilled?
– USGA: 15 – 30%
• Capillary porosity (Microporosity)
– What % of the pores are filled with water?
– USGA: 15 – 25%
What to look for in a soil test report
• Hydraulic conductivity (percolation rate) – USGA: minimum 6 in/hr
• Particle Density
– Density of the solid portion of the soil – Around 2.65 – higher if calcareous, lower if a lot of OM – Needed for porosity calculations
• Organic Matter
What to look for in a soil test report
• Quality Control Testing
– Particle size analysis with silt and clay combined
– Organic Matter
– Quick turnaround
Other Things to Consider
• What is the soil makeup of the sod?
• Thick cut or thin cut?
• Aerify and topdress with sand similar to rootzone
Reasons for Sand Field Failure
• Pre-installation
– Poor design / sand selection
• Too coarse – will be droughty
• Too fine – slow drainage, compaction
• Wrong particle size distribution
Reasons for Sand Field Failure
• Pre-installation
– Calcareous sands
– Too much / too little organic matter
– Poor design • Irrigation systems
• Drainage system
Reasons for Sand Field Failure
• During Installation
– On-site mixing
– No Quality Control testing
– Sod soil with high amounts of fines
Reasons for Sand Field Failure
• After installation
– Allow buildup of organic matter
• Shallow rooting
• Reduced drainage
• Divoting
Reasons for Sand Field Failure
• Improper maintenance
– Fertilizer program
– Irrigation scheduling
– Not removing cores
– Not topdressing enough
Reasons for Sand Field Failure
• Topdressing with the wrong material
• Match topdressing sand with rootzone
– If not, layers can develop (perched water table)
• No fines or gravel
Reasons for Sand Field Failure
• Loss of turf cover
– No cohesion between particles
– Rely on rhizomes and roots
Research Trial
• Kentucky bluegrass
• 2 Rootzones – USGA Sand
– Silt loam soil
• Evaluated divot resistance, tiller density, and root mass
Plant Growth Regulator Study
• Plant growth regulator - Reduce vertical shoot growth by altering hormone levels
• Trinexapac-ethyl (TE) - Inhibits gibberellic acid
– Side effects – increased tiller density and rooting
www.turffiles.ncsu.edu
Trinexapac-ethyl Applications
• Rate 0.5 oz/ 1000 ft2
• 28-day intervals
• 2 application regimes
– May – July (3 applications)
– May – Oct (6 applications)
Results
• TE applied from May – July reduced divot size most
– Sand: 10-20% reduction
– Soil: 10% reduction
• TE applied from May – Oct was not better or worse than untreated plots
Results
• Tiller Density
– TE treatments increased tiller density up to 15%
– Root Mass • TE applied from May –
July increased root mass by 10%
Nike Reuse-A-Shoe
Turfgrids (3, 5 g kg-1)
Netlon DuPont Shredded Carpet
Fiber Reinforced Sand Systems
Turfgrids
Fiber Reinforced Sand Systems
• Increases surface stability
• Popular on European Soccer fields
• Synthetic fibers sewn into existing turf – Every ¾”
– 7 inches deep
Fiber Reinforced Sand Systems
• 22 million fibers
• 25,000 miles of fibers on a single field
• 3% of field
• NFL fields
Fiber Reinforced Sand Systems
• Advantages
– Increase stability
– Less Divoting
– As field get worn, plays better
– Roots intertwine with fibers?
• Disadvantages
– Cannot core aerify
– Cannot re-sod
– Fibers tend to lay over
– Topdressing buries fibers
Final Thoughts
• Sand maintains good air and water balance even under compaction
• Sand-based fields prevent the disaster rain game
• Sand mix must be carefully selected to realize benefits
Final Thoughts
• Maintenance practices must be adjusted and intensified
– Manage organic matter
– More frequent irrigation
– More frequent fertilization
– Topdressing with proper sand
– Maintain turf coverage
– More expensive to build and maintain