Technical - Soil Biology “


Thatch Removed physically


Roots restricted to hollow core holes


Root break


Old top dressing compacted with iron band


Original rootzone killed by inorganic fertilisers and no oxygen


105 year old green managed chemically with hollow coring


Diseases occur because fungal pathogens have a lot of weak grass to attack and very few of the natural defence mechanisms to stop them


swimming in a sea of food. The plant does not need its associations with microbes to live which, coupled with the fact that microbes are killed by high salt index fertilisers, the lack of humus, the use of fungicides, excess water and compaction which deprives the microbes of oxygen, the removal of animals which replenish the microbes via excrement and near daily cutting, mean that the food chain cannot possibly survive.


We often find that sports turf rootzones have less than 10% of a healthy microbial biomass and that the total fungal biomass is much less than total bacterial biomass though, as we shall see, fungi are extremely important to your greens management programme.


How does healthy soil help the turf manager?


Disease management


If the grass dies, we all starve, so nature has worked out some clever tricks to keep the plant and food chain alive.


Broadly, there are four main mechanisms that plants working symbiotically with microbes have developed to prevent disease.


Thatch degrades naturally


Clean humus rich rootzone, with good biological diversity,


Roots grow in the whole profile


No compaction


Excellent drainage


No hollow coring. Vertidrain and sorrel roll only


108 year old green with good soil biology without hollow coring


Thatch is a great source of nutrient for fusarium, thatch fungus, basidiomycetes and other nutrient loving fungal diseases


124 I PC OCTOBER/NOVEMBER 2015 ”


Beneficial microbes form a barrier around healthy roots, which many pathogens cannot penetrate and some of the beneficial bacteria and fungi produce toxins to kill pathogens. These toxins are the source material for many new fungicides. Some microbes eat pathogens and the plant, and beneficial microbes send biochemical signals to each other when the plant is attacked to encourage the plant to activate its own defence mechanisms and produce plant hormones called phytoalexins to help fight disease.


There are, of course, specific remedies for each disease as they metabolise in different ways but, in general, diseases occur on sports turf because fungal pathogens, which exist partly to cull weak plants, have a lot of weak grass to attack and very few of the natural defence mechanisms to stop them.


Thatch and dry patch management


2cm of thatch on a hectare of greens contains about 200m3


of organic


matter that is full of excellent nutrients diluted with topdressing. Current wisdom is to hollow core or rip it out and replace it with topdressing plus organic matter full of excellent nutrients. Weird or what?


The simple solution is to convert thatch into humus as it is formed, releasing the locked up nutrient and providing a building block for future plant growth that holds moisture and increases cation exchange capacity. To do this, you need bacteria and fungi, which eat cellulose and lignin


Thatch is a great source of nutrient for fusarium, thatch fungus, basidiomycetes (the fungi that


produce the hydrophobins that cause a type of dry patch) and other nutrient loving fungal diseases. If the thatch is already full of beneficial fungi, the pathogens cannot get a seat at the table, so they cannot grow.


The end of hollow coring?


When the thatch has been degraded and converted to humus, it maintains a good biomass in the rootzone which, in turn, improves friability and drainage, thus negating many of the reasons for hollow coring.


Aeration is needed, of course, as it would be for a 200m3


compost heap


but, generally, once the process has started, bi-weekly or even monthly aeration with needle tines or a sorrel roller that do not upset the playing surface are all that is needed for thatch reduction and friable soil.


Grow perennial grasses not poa annua


If you analyse soil supporting poa annua greens, you find a bacterial biomass about ten times greater than fungal biomass, but soil that supports old established fescue, bent and rye grasses has a nearly equal amount of fungal and bacterial biomass. Fungal biomass increases when you start to degrade thatch and greenkeepers report a sudden sustained increase in agrostis or fescue grasses when they start to degrade thatch in situ, i.e. when the fungal population increases.


Research has shown that poa annua does not associate positively with mycorrhizal fungi, which gives perennial grasses a growth advantage. Growing in new grass or overseeding with mycorrhizal fungi not only reduces the time taken to grow in the grass but it also helps reduce poa annua ingress as the sward matures.


In future articles, we will explore the practicalities of creating and maintaining healthy rootzones and changing management practices to reap the benefits and cost savings to be gained by combining chemistry, physics and biological processes into turf management.


My thanks go to the professors and researchers at the universities of Oregon, Surrey and London for information contained, and especially to the greenkeepers and groundsmen who have helped us with their time, feedback and advice in developing this technology.


Symbio is dedicated to researching solutions to restoring the natural biological activity in soils and growing media essential to ensure the long term sustainability of food production and amenity plant resources for the world’s increasing population.


www.symbio.co.uk


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