Lack of effective aeration leads to poor root growth, poor grass growth and poor drainage
All grass swards are grown on soil / sand profiles that provide the appropriate environment structure for plant growth. This growing medium, commonly known as soil, is made up of proportions of soil solids (mineral and organic material) and soil pores (water and air).
Maintaining the correct balance of these components is critical for sustaining healthy plant growth. The spaces between the particles of solid material are just as important to the nature of soil as are the solids themselves (Brady & Weil 2002). It is in these pore spaces that air and water circulate, and help provide the plant with the necessary nutrients and air and water it requires to respire and grow. These pore spaces can vary in size and are generally classified into two sizes - macro pores (larger than 0.08mm) and micro pores (less than 0.08mm). Macro pores generally allow movement of air and the drainage of water and are large enough to accommodate plant roots and micro-organisms found in the soil. The ability to retain a good balance of macro pores in soil structure is essential for maintaining grass plant health. It is when these macro pores are either reduced in size by compaction or filled with water that we see deterioration in pitch playability and resistance to wear.
However, the main contributing factor that reduces and damages pore spaces in soil, is compaction, caused by compression forces normally associated with play
and use of machinery, particularly during wet weather periods. Over time these compression forces reduce the pore spaces so that air, water and nutrient flow through the soil profile is restricted, and leads to many problems associated with compaction.
Compaction can occur at varying depths. On winter games pitches there are two distinct types; one is compaction by treading (30- 60mm depth) and the other by smearing and kneading (30mm depth) when playing in the rain and bare soil surfaces (Adams & Gibbs 2000). Compaction has been measured down to depths of 120-150mm on horse racing courses.
In addition, compaction caused by vehicles, and this includes mowers, greens irons and myriad other machinery designed to treat cultured turf these days, has been measured much deeper than 150mm. Greens and tees
construction with heavy machinery, where minimum subsidence and a totally level surface is demanded can, in some cases, result in compaction panning as deep as 750mm.
Quasi-compaction pans associated with black layer iron pan and similar
chemically induced ‘compact’ zones also exisit. After all, they are impervious and prevent root growth just as well as any true compaction pan, can be a metre below the surface and develop wherever the soil chemistry and soil water oxygen content provides the correct (should that be incorrect) conditions. The extent of compaction is dependent on the soil type.
Clay, clay loam, silt and sandy soils will all compact, but the majority of compaction problems are associated with the heavier soils (clay and clay loams). There are a number of methods available to measure soil compaction and hardness:
• Cone penetrometers are devices that are pushed into the ground, measuring the resistance of the soil when inserting.
• Taking soil samples using density rings to measure soil bulk density.
• Clegg hammers that measures the impact of a weight dropped from a predetermined height.
Other indicators of compaction are changes in visual appearance, performance and physical properties of the soil and surface:
• Plantain weeds (Plantago major) seen in the surface generally indicate compaction problems.
• An anaerobic soil condition is formed that reduces root growth and restricts micro organism activity.
• Decreased water infiltration and reduced hydraulic conductivity that leads to surface water logging and ponding.
• Saturated soils have reduced soil strength, which often results in loss of ground cover.
The above conditions will adversely affect pitch playability in many ways, reduced ball speed, ball bounce, ball roll, player safety and, in the long term, damage the surface soil
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