Compaction & Thatch 1 hr (1)

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