must be hospitable, i.e. 5% humus, 25% air, 25% water, 45% mineral.
Fertility is much more than NPK out of a bag. Encouraging natural fertility is about optimising the environment to ensure that the unseen workers - the beneficial microbes - can maximise their contribution to nutrient availability in the root zone resulting in balanced, healthy turf growth.
No Air = No Oxygen = No Life
Compaction combines a physical barrier with the exclusion of air, which has far reaching effects on “life” and the ability of the plant roots to work effectively. Introducing air into compacted playing surfaces is essential if the full benefit of remedial treatments and the natural potential of the turf is to be realised.
Humus
Referred to as Colloidal Organic Matter, humus has three times the exchange capacity of clay colloids. Humus is a key component of a productive growing medium and is particularly important for:
- physical structure - improved tilth - availability of plant nutrients - increased water filtration - decreased erosion - less pollution
The key benefits of optimising the natural potential of the growing medium are healthier turf and less dependence on chemical inputs.
Clay Colloids
The clay colloids in soil are the exchange sites and consist of the smallest particles of clay, invisible to the naked eye, on which nutrients such as calcium, magnesium, sodium, potassium, trace elements and hydrogen are held. These nutrients are known as cations, are positively charged and are held in varying proportions on the negatively charged clay colloids.
Base Saturation
Base saturation measures the percentage make up of the cations on the clay colloid. As the exchange sites are always 100% occupied, the physical, chemical
and biological attributes of the soil will often be reflected in the relationship of the cations on the base. For example, a soil with high magnesium will tend to be sticky and difficult to work.
Understanding pH
pH is often erroneously associated with the lime content of the soil, but it is actually a measure of the amount of hydrogen on the base. The more hydrogen the more acid in the soil; the less hydrogen the higher the pH. However, it does not follow that high pH soil is necessarily high in calcium. The exchange sites can be occupied by: magnesium, sodium and potassium, all of which displace the calcium on the base and keep up the pH. Therefore, despite a high pH, plants can be short of calcium. pH measurement alone is an insufficient guide to the calcium status of the growing medium, hence my company’s Rootzone Survey looks at base saturation in detail.
Cation Exchange
Cation exchange is the process whereby plant roots absorb many of the essential nutrients. The process works through the secretion of exudates containing positively charged hydrogen ions, which swap in for the positively charged cations of calcium, magnesium, sodium, potassium and trace elements. 70% of cations absorbed by the plants go through the exchange process; hence, the imbalances on the base prevent balanced uptake, with adverse effects on the turf ’s ability to overcome stress, resist disease and produce high quality, durable playing surfaces.
Important parameters of rootzone revealed
Sand based and soil based growing mediums present very different management challenges. Measuring the physical characteristics of the rootzone in greater detail can provide a valuable insight into the contributory cause of problems and indicate the most appropriate remedial action.
Sand Particle Size
Sand based rootzones present a management challenge in themselves; more so if the actual sands used are widely divergent from the recommended
standard. A wide range of particle sizes will compact, as in mixes designed for concrete. Sands for sports turf use are closely matched to produce a balance of water retention and gravitational drainage.
Benefits of a Root Survey
A good survey, carried out by a reputable company, provides the starting point for cost effective turf management which prioritises rootzone care by natural means, reducing the need for chemical dependence. For example, our approach enables managers to develop rootzone maintenance programmes more carefully matched to underlying construction - soil or sand - and to the pattern of use and to the needs of the varieties of bents, fescues and rye grass grown.
Which Area to Survey
Even in areas of similar soil type, the performance of sportsturf can differ markedly from area to area. We recommend a minimum of three surveys so that a comparison is made between the best and worst areas, and an assessment can then be made of the underlying causes of disappointing performances with appropriate recommendations for remedial action.
Follow Up
Your advisor should be able to work through the survey results with you, identifying how best to achieve the objectives of enhanced player
satisfaction from the sportsturf in your care. Be very wary if your supplier ignores the results of a rootzone survey, or considers it ‘not right for your situation’.
About the author: Andy Turnbull is Managing Director of The Great Turf Company, specialists in Activated Microbial Turf Management. Email:
andrewt@greatturfcompany.com www.greatturfcompany.com
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