Technical - Soil Biology
reduces Cation Exchange Capacity (the nutrient holding capacity of the rootzone) requiring more fertiliser applications which, in turn, produces more thatch.
Finally, introducing inert, sometimes sterilised, material creates the bacterial dominant rootzone favoured by annual grasses, all increasing future maintenance costs.
The Alternative Option
There is another option adopted by many golf course and sports pitch managers that have been successfully managing their playing surfaces for many years without deep scarification or hollow coring and heavy topdressing, as the brief case studies within this article show.
The alternative to physical disruption, thatch dilution and rootzone replacement is to degrade thatch and encourage natural processes to decompact the rootzone and incorporate these processes into the daily management of the pitch, greens or any grass sports surface.
Healthy grassland soils comprise 50-60% soil particles, 15-25% air space and 15-25% water. You only have to take cores out of the rough of most golf courses to see that it is almost thatch free and friable because natural processes are at work. The key to easy turf management is to get these processes to work in the largely artificial environment of a sand based rootzone.
To successfully implement this strategy, the first misconception to knock on the head is that organic matter is bad. It is not. Organic matter in the rootzone comprises roots, humic compounds, partly degraded humus and soil microbial life which, by itself, can weigh up to 3 tonnes per hectare. All the humic compounds start life as thatch which, when degraded, converts to humus and beneficial organic acids.
Thatch should more properly be called organic material, the source, when degraded, of nearly all beneficial organic matter. The chemical, physical and biological actions of soil organic matter are contained in a previous article in Pitchcare
https://www.pitchcare.com/magazine/soil- organic-matter-is-good.html
So how can greens and pitches be managed without heavy disruption?
Thatch degrades easily and converts to humus in situ if the necessary fungi and bacteria are
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You only have to take cores out of the rough of most golf courses to see that it is almost thatch free and friable because natural processes are at work
present. If the microbes needed are missing, then products containing thatch-eating fungi and bacteria have been available for over twenty years and there is a wide range of options from microbial inoculants to compost teas available to the turf manager to degrade thatch. The limiting factor in thatch degradation is usually oxygen.
Oxygen the best biostimulant
The most effective way to get oxygen evenly distributed throughout the rootzone is by frequent tining with 6-8mm block tines - which hardly disrupt the surface; regular use of a sarrel roller that penetrates to the bottom of the thatch layer every 2-3 weeks will suffice. This may be augmented with slitting when moisture levels allow.
There are also a number of liquid applications that contain high numbers of oxygen atoms so, when sprayed, allow oxygen to become available throughout the rootzone
Hollow coring does not always oxygenate the soil. You can see from the pictures in figure 1 that hollow coring once or twice a year has very little effect on black layer. The black layer has not broken down because oxygen has only travelled a couple of millimetres from the tine hole. However, when regular micro tining and microbiology was applied via compost teas, the rootzone became clean, friable and humus rich in the space of a year.
Nature works in several ways to create the correct air and water spaces in the rootzone.
Bacteria and fungi produce polysaccharides to help them adhere to surfaces and to prevent them from drying out. The polysaccharides are sticky substances which clump fine soil particles together, forming air space in between.
Fungal hyphae grow through the rootzone pushing soil particles apart. There is over one tonne of fungi per hectare in a healthy rootzone and many fungi form mycorrhizal associations to transport nutrients and water through the rootzone to benefit the plant.
Nematodes often get a bad press from turf managers, but very few are plant parasitic. Most live on bacteria and fungi or other nematodes. Nematodes play an important role in soil improvement. They are larger creatures up to 0.5mm long and, as they move through the rootzone, they push soil particles apart, depositing ammonium as they go. Root hairs then colonise the space and further improve friability.
Earthworms, most of which do not form casts, also create wide air spaces and drainage channels.
Putting fungi to work
Thatch is mostly lignin which needs fungi and actinomycetes to digest it and break it down. Without fungi, dilution with sand will have a very limited effect. You can see this from the pictures in figure 2. A green with very deep, dense thatch was hollow cored twice a year for two years and 200 tonnes/hectare p.a. of sand applied. With almost no positive result. After two years, the greenkeeper switched to a biological approach. He applied thatch eating fungi, stopped hollow coring, reduced sand inputs to 120 tonnes p.a. and tined every two weeks with 6mm block tines. After two years of this regime, the thatch had almost completely gone leaving an aerated, friable rootzone.
Creating a fast draining rootzone
To maintain healthy, free draining rootzones, you need a minimum of 2-2.5% w/w humus or humic compounds and, until the thatch is completely mineralised, which can take up to 30 years, humic compounds show up on the loss on ignition test to measure “organic matter”.
The positive effect of humus cannot be overemphasised. It turns the rootzone to a rich brown colour, so it is easy to see if you have enough.
Figure 1
Figure 2 PC FEBRUARY/MARCH 2016 I 117
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