Technical
“ Bruce Brockway
We all know what we mean by ‘soil and water’, but it only refers to two of the three ingredients necessary for plant growth - the third being ‘air’. If you only have the first two, you have a drainage problem! The purpose of drainage could be said to introduce air into soil.
Bruce Brockway, Secretary of the Land Drainage Contractors Association, offers a back to basics revision class
120 I PC JUNE/JULY 2015 Land Drainage
Soil, water and... P
lant roots need soil, water and air to be able to absorb nutrients from the soil. As a growing medium, soil should consist of roughly 50% particles, 25% water, and 25% air. The
water and air should be in the spaces between the particles.
Soil Particles
Soil has mineral particles of different sizes. The smallest are clay particles, next are silt, with the largest being sand. Whilst some soils can have only one size of particle, like pure sand, most soils will have a mixture of particles. Soil texture
is classified according to the respective percentage of these particles. For example, if a soil is 60% silt, 20% sand and 20% clay, the soil texture is described as ‘silty loam’.
Ideally, an additional component in the solid portion of soil is organic matter made up of humus, roots and organisms. This organic matter is usually only as little as 5%, but it is important to give soil a structure by helping particles to clump together to form crumbs of various sizes. The glues developed by organisms feeding on the organic matter produce the cement to hold particles together as structural units known as ‘peds’.
Sadly, in the case of sportsturf, in spite of the best efforts of groundsmen and greenkeepers to create and maintain these perfect conditions, we go and spoil it all by playing sport on it!
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