Soil Askham Bryan’s
STEVE PRINN says that to manage
turfgrass we need to have a basic
understanding of
soils and the impact its condition has on the grass
FUNDAMENTALS
IN order to manage turfgrass we need to have a basic understanding of soils and the impact that the soils condition has on the grass. Brady and Weil (2002), list six things that plants obtain from soil, in no particular order, these are;
• Physical support • Air • Water • Temperature moderation • Protection from toxins • Nutrients
The physical support is provided by
the root system anchoring the plant to the soil, this helps to keep the plant 'in- situ'. Several benefits arise from the plant remaining in the soil, not least of which is that the surface remains playable, however; traction, erosion control and a degree of “shock absorbency” are also important to the playing surface and its performance, without this the playability of the surface may be compromised. Plant roots need to respire to obtain energy, like us they also take in oxygen (O2 dioxide (CO2 the soil, CO2
), and give out carbon ). Through the pores in escapes and O2
enters
the soil profile. This process is also helped by maintenance practices such as aeration which assists gaseous exchange to take place. It is not only the plant which requires O2 from the soil. Soil micro-organisms also require O2
and release CO2
as the plant population (Rowell, 1994). The greatest need for O2
in
fact, microbial populations have a similar demand on the O2
in the soil lies
in the upper 100mm of the soil profile where there is the largest concentration of soil microbes and turfgrass roots. Poor O2
perched water table.
• Compacted, heavily textured soils are likely to have poor pore spaces this effects the rapid transmission of water through the soil profile.
Under anaerobic condition, a process known as reduction will occur, this causes denitrification and the also the production of organic compounds which may affect plant growth. The appearance of mottling in the soil is an indicator that this process is under way. Patches of grey, orange and dark brown indicate poorly drained soils. One common symptom of this process known all too well, by many turfgrass managers is the formation of Black Layer (figure I), which occurs when sulphur or sulphur derivatives, such as sulphate are reduced to the sulphide in the form of hydrogen sulphide. This gas combines with metal ions in the soil like iron (Fe), to form the corresponding sulphide.
Black layer formation on a golf green, notice also the orange mottles.
concentrations in the soil,
lead to what is frequently termed, anaerobic conditions this usually occurs in heavily textured soils. The critical time for this, is curiously in the summer during wet periods not in the winter - demand for O2 winter. O2
is not as high in the is usually restricted by one, or
a combination of the following: • A soil with a high water table.
• The soil overlies a clay subsoil which holds up the water table artificially, this is more commonly termed a
The soils ability to hold or release moisture is vital to the turfgrasses survival. It is known that plants consist of between 75% to almost 90% moisture but a decrease in only 10% can cause the death of turfgrass. Water availability is therefore critical to turfgrass health. The amount of water present in the soil also has an effect on the physical properties of the soil. For example the strength of the soil will increase as the soil becomes drier.
The moisture status of the soil depends on the type and arrangement of the soil particles as this dictates the
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