Imagine a jar full of 10mm marbles and a second jar full of marbles with a size from 20mm down to 2mm. The first jar could be filled with more water than the second due to the closer packing of the second
coring the turf to break through the layer, although it is nearly impossible to soil exchange the whole surface. The use of rootzone washed turf may be an answer as would seeding, but both methods require favourable weather and timescales respectively.
Pore space
Often we see samples of sandy soils that, in the hand, would appear free draining. In practice, these soils often do not drain. This is often due to a wide range of particle sizes and shapes that produce a resultant low level of pore space. If a sandy soil has an even particle size distribution from sands to clay then the alarm bells should ring as the pore space, and hence drainage, may be poor. This is due to the close packing of the wide range of particles filling all the gaps. As an example, imagine a jar full of 10mm marbles and a second jar full of marbles with a size from 20mm down to 2mm. The first jar could be filled with more water than the second due to the closer packing of the second. The resolution of this problem would
be to incorporate a narrow range particle size sand to create a significantly increased percentage over the rest of the finer soil particles to open up the pore space. The use of aeration and penetrant wetting agent would also be of help. Sometimes, we see the results of the
wrong type of sands used and the worst culprit would be soft builders sand on sports pitches. This, if applied, often fills any pore space or fails to ameliorate and tends to make the drainage worse. The structure of a soil will invariably have an impact on pore space due to fissuring and the presence of soil crumbs. Many new constructions have little rootzone structure and if the texture/depth is not correct then poor drainage will follow. Over time, as the work of soil fauna, flora and plant roots takes place the soil/rootzone may become more structured and drainage improves. However, sandy soils can have poor structure and therefore needs aeration to keep channels open and air in the profile. Silt soils develop structure but often weakly, being prone to compaction and hence require aeration and
decompaction. The best soils for structure can be clays, but their drainage rates can be very low, especially in wet and compacted conditions. Amongst the varying characteristics/properties of sand or clay dominated soils/rootzones, one should also not neglect the huge role that is played by organic matter in soils that drain due to their textural or structural characteristics (another article in itself).
Conclusions
Sands continue to be the most appropriate rootzone/soil ingredient for fine turf. However, a failure to understand basic soil physics can result in poor drainage rates, thatch build up and ingress of undesirable grass species. The playing ability will be compromised. This article showed how layering, critical tension and pore space could have a direct influence on the drainage potential. Using these principles, hopefully better decisions and maintenance operations can be the result.
An AFT 45 on a compact tractor has two applications
1 Fitted with its chain and boom for wider and deeper trenches 2 Fitted with its slitting wheel for narrow slit drainage
AFT Trenchers Tel: 01787 311811 email:
info@trenchers.co.uk www.trenchers.co.uk
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