florida friendly lawn management...why fertilize? • lawns need nutrients to grow in a healthy...
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Florida‐Friendly Lawn ManagementLaurie Trenholm, Ph.D.
Urban Turfgrass BMP SpecialistUF‐IFAS
2018 MG Turfgrass Field Day• Tues, Oct 16 9am‐3pm• Plant Science Research and Education Unit• 2556 Hwy 318, Citra FL• Morning research plot tours, afternoon indoor education sessions
• Meet the IFAS turfgrass researchers and pick their brains!
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Our Florida Lawn Grasses
Bahiagrass(Paspalum notatum)
• Advantages– Good drought tolerance– Low fertility requirements– Low maintenance– Tolerant of sandy, infertile soils
– Establishes from seed
Bahiagrass
• Disadvantages– Produces abundance of seedheads
– Open growth habit encourages weed competition
– Susceptible to mole crickets– Coarse stems are difficult to mow– Not wear tolerant
Centipedegrass
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Centipedegrass• “Poor man’s grass” – very low input• Watch fertilizer‐ very low rates needed and too much leads to centipede decline
• Few insect and disease problems• Light green color• Slow growing and prostrate• New cultivar ‘Hammock’ developed primarily for use in south FL
St. Augustinegrass(Stenotaphrum secundatum)
St. Augustinegrass• Best shade tolerance of warm‐season grasses, but varies by cultivar
• Good salt tolerance• Tolerates wide range of soil pH• Establishes quickly from sod• Deep green color• Requires irrigation much of the year to stay green and healthy
• Chinch bugs becoming resistant to pesticides
Sugarcane Mosaic Virus• Outbreaks multiplt
counties around the state• Floratam most affected
cultivar and will usually result in death
• More resistant Palmetto and BitterBlue, which may get the virus but do not suffer the damage as Floratam
• No chemical treatments available
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St. Augustinegrass Cultivars
• Floratam• Bitter Blue• Palmetto• Delmar• Seville• Captiva
Empire Zoysiagrass
Zoysiagrass• Low‐growing, dense• Very responsive to nitrogen – lower
rates needed than for St. Aug• Shade tolerance similar to Floratam• Hunting billbug pests• Susceptible to large patch disease• Tends to get thatchy• Needs about same amount of water
as St. Aug• Mowing height 2‐2.5”• Empire most commonly used, but
other cultivars in small amounts of production
Empire Zoysiagrass
• Goes into dormancy throughout winter in central and northern Florida
• Greens up slowly in spring (large patch issues can compound this)
• People will want to apply extra N fertilizer to green it up – this is not good!
• Homeowners managing this grass themselves will have to become more familiar with disease management
Nutrients Required for Turfgrass Growth
From Environment:
Carbon
Hydrogen
Oxygen
Nutrients Needed From Soil or Fertilizer
Micronutrients:IronManganeseBoronCopperMolybdenumZincNickel
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Macronutrients:Primary:
NitrogenPhosphorusPotassium
Secondary:Calcium MagnesiumSulfur
Why Fertilize?• Lawns need nutrients to grow in a healthy condition
• Grasses grow and turn green in response to fertilizer
• A properly fertilized lawn is your best defense against weeds
• A properly fertilized lawn is your best protection against storm water runoff
• This does not mean overfertilization!
When to Fertilize?• 1‐4 times a year:
– Spring when growth begins and after danger of frost– Summer – apply iron or low amounts of nitrogen fertilizer – fertilizer important during times of growth, but may not be needed depending on soil characteristics and grass species
– Fall – potassium beneficial, imparts cold tolerance to grass
– Winter‐ depends on location in state – DO NOT fertilize dormant grass with nitrogen (no fertilizer mid Oct‐April in North Fl and Nov‐ end of March in central Fl)
• South Florida may fertilize year‐round
Warm Season Grass Growth
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What About Other Nutrients? • Soil test can tell you what is needed• Turf need for calcium & magnesium low• In high pH soils, iron & manganese may be limiting‐ for best results, these should be applied in a chelate form (not oxide form)
Annual Fertilization Rates for Lawngrasses
(Lbs. of N per 1,000 sq. ft.)Central North
Bahiagrass: 1‐3 1‐3Centipedegrass: 0.4‐3 0.4‐2St. Augustinegrass: 2‐5 2‐4Zoysiagrass: 2‐4* 2‐3
Most zoysia cultivars should get no more than 2 lbs yearly
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How Much to Apply Each Time
• Frequency of application: 1‐4 times yearly • Each application: maximum amount to apply is 1 lb N per 1,000 sq. ft. if fertilizer has slow‐release N
• Only fertilize during the growing season
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Fertilizer Calculations• Divide your yard up (front, back, sides)• Determine square footage of each area
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40’
25’
Fertilizer Calculations• Look at fertilizer analysis on bag (ex. 15‐0‐15)• Take the amount of N (15% in this case) and divide it into 100.
• This gives you 6.6 – this is the pounds of fertilizer that you need for 1,000 sq. ft. to apply 1 lb. N
• This works for ANY fertilizer analysis
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Fertilizer Calculations• To apply the correct amount:
– Take half of the total amount of fertilizer:• 15% = 6.6 lbs fertilizer per 1,000 square feet• Half of this = 3.3 lbs fertilizer in spreader
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Fertilizer Calculations
• To apply the correct amount:Take the remaining 3.3 lbs, put in spreader and go back and forth at 90o angles
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Two Ways That Fertilizers Can Pollute
1. Leaching through soil profile – this is what nitrogen will do in sandy soils
Two Ways That Fertilizers Can Pollute
2. Surface water run‐off
Turfgrass Fertilizer BMPs• Keep fertilizer off impervious surfaces• Maintain a buffer zone around water bodies• Apply only the correct amount – more is not better!• Soil test – know your pH and soil available nutrients • Low (or no) phosphorus!• Only fertilize during the growing season• Irrigate fertilizer in with about ¼” of water• Do not fertilize newly planted grass for 30‐60 days
Sweep Up Fertilizer Spills
200 linear feet X 5 feet wide mower = 1,000 ft2
2,000 grams clippings (dry weight)3.5% nitrogen in the clippings =
70 grams nitrogen =0.15 lbs nitrogen
Nitrate Leaching from New vs. Established Grass in 2005
0
100
200
300
400
2-May
16-M
ay23
-May
1-Jun-05
7-Jun-05
14-Ju
n-05 20
june 0
528
-Jun-05
5-Jul-
05
0.512
0
5
10
15
20
25
0.3 lb 0.66 lb 1.3 lb 2.0 lb
Newly Planted Sod Established Sod
Nitrogen Rate Study ‐ Nitrate‐N Leaching from Floratam
0
1
2
3
4
5Yr
1 F
C1
Yr1
FC2
Yr2
FC1
Yr2
FC2
Yr2
FC3
Yr2
FC4
Yr3
FC1
Yr3
FC2
Yr3
FC3
Yr4
FC4
1 lb N4 lb N7 lb N10 lb N
Nitrogen applied as 100% soluble urea
NO
3-N
Lea
ched
(kg
ha-1
)
Trenholm et al. 2009
Irrigation BMPs
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Overwatering• Increased disease issues• Root rot and stunting• Weak turf stand• Increased weeds
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How Frequently to Water
Varies due to:– Season– Soil type– Shade– Rooting depth– Insect or other
pests– Other stresses
Seasonal Frequency of Irrigation• Zazueta, Miller, and Zhang*:
Winter 4.5‐11.6Spring 2.7‐6.9Summer 2.7‐2.9Fall 4.8‐11.6
*For St. Augustinegrass with a 6” root system under low irrigation regime in the Tampa Bay area
Irrigation Frequency• Watch grass for signs of stress• Follow watering restrictions!• You may water “hot spots” with hose if needed and if not prohibited by local restrictions
How Much to Water
•Apply 1/2” to 3/4” when turf shows symptoms of wilt
•This should not vary‐ only frequency varies!
Short, frequent irrigations
Longer, less frequent irrigations
Irrigation System Efficiency
• Calibrate systems to ensure uniform coverage
• Check for broken heads, etc• Check for landscape plants that may block sprinkler from reaching grass
Time Line for Irrigation for New Sod Plantings
Time Frequency DurationFirst 7-10 days 2-3 times
dailyShort (5-10 mins)– try to keep plant material from drying out
7-10 days after planting
Once a day Apply ~ ¼” water – more will be wasted due to short roots
Next 7-10 days Every other day
Apply ~1/4 to ½” of water
3-4 weeks after planting
1-2 times weekly
Apply ~ ½” water
Which Grass Has Better Drought Tolerance?
• All of our grasses need water to stay green (about the same amount!)
• Survival often depends more on soil organic matter, shade, rooting depth than species
Severe Watering Restrictions• Do soil amendments help?• Research on these is often not clearly stated• Often, no significant benefits seen• When possible, incorporate organic matter prior to planting sod/seed
• Not practical to try to topdress after turf establishment to add organic matter
Mowing
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Mowing BMPs • Mow at the correct height for the species
– Mowing too low stresses the grass and forces it to use up all saved reserves for shoot growth
– Mowing high increased root depth
Mowing Heights• St. Augustinegrass Standard Height Cultivars:
– Floratam, Bitter Blue, Classic, etc.– 3.5 – 4”
• St. Augustinegrass Dwarf Cultivars:– Captiva, Delmar Seville– 2‐2.5”
• Bahiagrass: 3‐4”• Centipedegrass:• Zoysiagrass: ~2”
Mowing• Only remove 1/3 of the leaf blade at any one time– Grass at 6” should have no more than 2” removed
• Keep mower blades sharpened• Do not mow wet grass• Commercial mowers should be washed off between properties (do you ever see this?)
Scalping is a Major Stress
Two Types of Stresses
• Biotic– Insect– Disease– Nematode– Weed
• Abiotic– Drought or over‐watering– Excess or insufficient fertilization– Mowing (scalping, dull blades)– Soil compaction/pH or other soil issue– Temperature extremes– Shade – Traffic– Dog Spots– Standing water/submersion– Saline (recycled/ocean) or poor
quality water
Managing Turf in the Shade
• Remove shade sources (trimming trees)• Reduce traffic in shaded areas• Increase mowing height if possible – more shoot tissue for photosynthesis will help turf perform better
• Reduce irrigation in shaded areas• Reduce fertilization – trying to promote shoot growth with high fertility will further stress the grass
Shade Tolerant Turf
St. Augustinegrass = zoysiagrassCentipedegrass
BahiagrassBermudagrass = Seashore
paspalum
St. Augustinegrass Shade Tolerance
• Seville, Delmar, Captiva–Bitterblue
• Palmetto–Floratam
The “New” Urban Soils• Retention pond soils typically very high pH‐ 8 or higher
• Become very compacted‐ impedes root growth
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Dealing With High pH
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Dealing With High pH• Micronutrients iron, manganese not available• Phosphorous may also be limiting• Micronutrient deficiencies cause interveinal chlorosis
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Dealing With High pH• Difficult to lower pH effectively• Elemental sulfur‐ forms sulfuric acid in presence of sulfur‐oxidizing bacteria
• Short term duration• Organic matter – humus, peat, peat moss• Ammonium sulfate as N source
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Dealing With High pH• Application of ammonium sulfate, biosolids as N source
• Topdress with compost, organic matter• Application of soluble or chelated iron and manganese
• Foliar fertilization (N and micros)• Watch for P deficiency
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Compacted Soils• Lack of oxygen for roots
• Roots can’t grow• Water, other inputs can’t penetrate
• Can form solid “hardpan” layer
• Dries out• Low microbial activity
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Dealing With Compacted Soils• Aerate/topdress• Consider foliar fertilization since roots will be compromised and may be difficult to work granules into soil
• Reduce irrigation run times to avoid runoff ‐irrigate in segments that let soil dry out to avoid runoff
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Why Do We Aerate?• Compacted soils• Improves roots (increases air)• Do Florida soils get compacted?
Warm‐Season Grass Growth Curve
Temperature Extremes• Warm season grasses inherently designed to grow in hot, high light conditions
• They have temporary cessations of growth when temperatures drop and/or daylength shortens
• Time agronomic programs to complement this basic biology, not attempt to offset it
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What Is This Stress?
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The “New” Urban Soils• Retention pond soils typically very high pH‐ 8 or higher
• Become very compacted‐ impedes root growth
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Dealing With High pH
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Dealing With High pH• Micronutrients iron, manganese not available• Phosphorous may also be limiting• Micronutrient deficiencies cause interveinal chlorosis
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Dealing With High pH• Difficult to lower pH effectively• Elemental sulfur‐ forms sulfuric acid in presence of sulfur‐oxidizing bacteria
• Short term duration• Organic matter – humus, peat, peat moss• Ammonium sulfate as N source
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Dealing With High pH• Application of ammonium sulfate, biosolids as N source
• Topdress with compost, organic matter• Application of soluble or chelated iron and manganese
• Foliar fertilization (N and micros)• Watch for P deficiency
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Compacted Soils• Lack of oxygen for roots
• Roots can’t grow• Water, other inputs can’t penetrate
• Can form solid “hardpan” layer
• Dries out• Low microbial activity
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Dealing With Compacted Soils• Aerate/topdress• Consider foliar fertilization since roots will be compromised and may be difficult to work granules into soil
• Reduce irrigation run times to avoid runoff ‐irrigate in segments that let soil dry out to avoid runoff
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Why Do We Aerate?• Compacted soils• Improves roots (increases air)• Do Florida soils get compacted?
What Is This Stress?
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The Burning Question About Dogs and Grass
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The Burning Question About Dogs and Grass
• High salts and N produce burned grass in areas where urine is concentrated
• How to repair?– Water in with hose if possible– Encourage dogs to have specific area to use– Replace damaged areas with stolons or plugs– No soil amendments that are effective– Not related to dog’s diet
What Are the Brown Spots in My Lawn?
• Is there evidence of a pattern from a spreader, mower, sprayer, irrigation head?– Look for mechanical injury or applicator error
• Look at site conditions (shade, compacted soils, wet soils)
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What Are the Brown Spots in My Lawn?• Is the injury random in shape and size or does it recur in multiple locations?– Check for insects
• Look at roots – are they black, rotting (fungal disease)or truncated (soil born insect or nematodes)
• Does shoot system have evidence of chewing on leaves (insects) or rotting (fungal disease)
• Is shoot system dried out and chlorotic or necrotic?
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