Developing and maintaining a turf root system

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The development of turf root systems is a much talked about topic amongst Turf Managers along with its level of importance, but rarely do Turf Managers dive deeper into the topic to get an in-depth understanding for their venues turf root system and how they can improve its depth & vigor to improve the overall presentation and durability of their turf surfaces.

The root system has two main jobs – to provide the turf foliage with all the nutrients it requires & to source water the plant requires to survive.

There are always areas at a turf facility that come under heavy usage and when there is a good root system present to anchor the turf the sustainability of the turf is always far better with greater ability to recover. In Australia we often face water shortage issues whereby turf surfaces can dry out excessively, a good root system present will assist in stabilizing the soil until the next application of irrigation or rainfall, in this situation if there is a shallow root system present, large divoting would occur and the integrity of the surface would not be maintained.

The management of aeration, thatch, and irrigation combined are the principal factors in maintaining and developing a deep and vigorous root system. In any turf situation the root system is the key in supporting the growth of healthy turf, and for providing the turf with the ability to deal with all the stresses that it encounters on a day to day basis.

Based on this, a simple conclusion can be made;

 “Any turf surface that has a deep and vigorous root system will have very little problems”

Its also worth pointing out that regardless of your turf situation or facility usage the principals of developing and maintaining a healthy root system can be applied to all areas of sportsturf regardless of the venue or surface being prepared.

It is important to note the different roles that both the root hairs and ‘tap roots’ play in supporting growth of a turf surface. It’s the root hairs that predominantly allows the root system to be able to take up nutrients for the plant to survive well, and it is both the root hairs and ‘tap roots’ that find water for the plant. Additional to this, the root system stores excess carbohydrate for the plant, along with producing plant hormones cytokinins, gibberellins and abscissis acids to send to the shoots in order to regulate growth. The effectiveness of the root hairs is short lived and to keep the root system functioning well new root hairs need to be continually produced to keep the nutrient and water uptake to optimum levels.

There is a common saying that “roots chase water” the reason that roots chase water for the plant is there is a reward system that exists, the more water that the roots find for the plant the more the water finding roots get rewarded by the plant with a supply of the plant hormone Auxin to grow and prosper – this process continues, the more water the roots chase and find, the more Auxin they get rewarded with. This is why good irrigation practices is said to be so important – deep infrequent irrigation results in roots growing deep into the soil profile looking for water for the plant in order to get their reward.

It has been proven over time that root systems of turf grass (both warm and cool season grasses) are annual in nature. A root system will grow, develop and die off within a 12 month period. This means once a Turf Manager has spent time developing and growing a deep and fibrous root system means that it will not be in place for ever and growing a good root system is an ongoing task. This is a very important point not understood by many.

There is a difference in how the root system of warm and cool season grasses revolves over a 12 month period, which is mainly based on soil temperature. During spring the root system of cool season grasses do their best development when soil temperatures are around 16-17 degrees. As soil temperatures rise as the summer months become nearer, the root growth of cool season grasses slow and eventually stops. When compared to warm season grasses, a similar process occurs, however the old root system dies off at a faster pace, a progression known as spring root decline occurs.

There will be no activity of the root system of warm season grasses until soil temperatures reach 17 – 18 degrees, which occurs at around the same time that most warm season grasses break dormancy. Optimum growth within the root system of warm season grasses will occur when soil temperatures are between 24 – 30 degrees. In many countries that have warm season grasses, this will be most of the summer months.

Restrictions on developing a better root System
The question that most Turf Managers often ponder over is how they can improve their root system to ultimately provide a better turf surface. Before going on and looking at ways to improve your turf’s root system some influencing factors on the potential of the root system to develop should be understood.

Plant species

The type of turf being maintained will have a major influence on its ability to grow and sustain a deep and fibrous root system. Genetically speaking, warm season grasses have greater ability to grow a deepier root system than cool season grasses. There are also differences when comparing different varieties of warm season grasses, and the same for cool season grasses. For example, some turf facilities in Australia and New Zealand have 100% Poa annua surfaces which is known for having shallow root systems as this is a genetic trait of this grass which ultimately will not allow these turf surfaces to develop a good root system regardless of the maintenance practices being applied. On the other hand perennial rye grass is know for producing a deeper root system in comparison as the genetics of the plant allows this. Turf Managers should understand their grass well and be realistic with expectations with the quality of their root systems.

Growing Medium Make up 

Another major influencing factor on the development your facility’s root system is the growing medium that you are required to work with. We know that turf grass roots like to grow in air space within the soil, and we also know that roots like to ‘chase water’ providing the growing medium is not saturated. Some facilities built many years ago often have poor soil make ups, and have poor drainage making it difficult to establish a good root system. On the other hand some of the newer facilities constructed using good budgets using good materials such as USGA specified sand have unlimited potential to sustain good root systems long term – a good quality sand provides good levels of non-capillary pore space for roots to grow into, resists compaction, and over time when managed right good levels of microbial activity will be present. On the other hand, sporting surfaces constructed on soils containing large amounts of clay & silt lack air space, lack drainage, and compact easily are all limitations in being able to grow a deep a vibrant root system. Those battling the difficulties of managing a turf facility built on poor soil should be realistic with expectations in relation to growing a good root system.

Thatch levels

Turf areas with high levels of thatch are very restrictive in their ability to produce a deep root system. Thatch is said to hold around 33% moisture, most soil profiles will range somewhere between 18% and 28% moisture content at field capacity – this is considerably lower than thatch. This basically means any growing medium with an excessive thatch layer will likely result in a short root system where roots live in the thatch as the thatch layer has a higher moisture retention than the soil profile itself meaning the roots will have no reason to grow deep as they are being well accommodated in the thatch & are happy to live there on an ongoing basis.

Irrigation Management

Turf facilities often have varying types of irrigation systems differentiating between automatic and manual systems. Regardless of the irrigation system in use it is vitally important that Turf Managers understand their systems capabilities including their outputs & their accuracy. If irrigation systems do not function well it will have a negative effect on the development & sustainability of the root system. Inefficient irrigation systems result in inconsistent outputs which can lead to either excessive plant stress through lack of water or waterlogged soils through overwatering with both scenarios having negative effects on root development.

Climate & Soil temperatures 

The growing conditions and air temperatures have a major influence on our ability to grow a good root system. During periods of low light intensity, the overall performance of the plant is restricted and in severe cases it goes into survival mode in the form of dormancy which case there will be no development of the root system, if anything the root system will be reduced/damaged during these times. As a rule, the more the turf is growing the better the chance the root system will too. Good growing conditions coupled up with good maintenance are major influencing factors. As mentioned above soil temperatures need to reach a certain level before both warm and cool season grasses root systems will be active – this is influenced by air temperatures and expectations should not be too high until soil temperatures reach the required levels. Its also worth noting soil temperatures will always be a few degrees lower than regular air temperatures.

Other environmental influences such as heat stress, drought stress, and water logging will result in sending the progress of the root system backwards. 

Pests and disease

Pest and disease activity have potential to restrict the development of the root system.

The roots are required to provide support to assist recovery from damage from pest and disease attack. The plant mobilizes nutrients from the root system to repair the damage from pest attack in the crown, rhizomes, leaf and stolons.

The activity of nematodes should always be considered. Nematodes are small insects that attack the root systems of turf that are difficult to identify and often attack the root system as a secondary pest (after the plant is already under attack from another disease or insect)  The only real way to find out if nematodes are causing you an issue is take soil samples and send away to a certified laboratory for testing to get an indication if numbers present are causing any issues.

In order to prevent damage from pest attack, the usual principals apply – like taking an Integrated Pest Management approach instead of reverting straight to chemicals to solve the problem. There are other options such as biological controls, non-pesticide controls (natural extracts) it is also important to understand your grass species threshold numbers and working with it. It is important to maintain optimum plant health and including good maintenance practices before pesticides are considered.

Above all, the stronger the root system is the more resilient the plant is, which in turn will establish a higher threshold against pest attack, and the faster the recovery will be when attack does take place.

Developing a better root system

In order to develop a deep and vigorous root system, the following rules need to be adhered to;

  • Ensure your turf facility is irrigated deep and infrequently – this will ensure the roots will grow deep looking for the moisture for the plant, so in turn it is rewarded with a ‘feed’ of the plant hormone Auxin. In the event that your turf surface is watered shallow and frequently, the roots will have no reason to grow deep as all the water the roots require is in the surface of the profile. By Imposing a mild amount of moisture stress on the turf surface on a regular basis will encourage the roots to grow deep looking for water, this is most preferable throughout spring as this is when the root activity is at its greatest and it also helps the plant to harden up leading into summer
  • Minimize thatch at all costs. Thatch reduction and maintenance should involve using all the methods available and a program should be undertaken to keep it in check. Practices such as mechanical dethatching, hollow tine coring, frequent sand topdressing, increasing microbial activity are important practices in maintaining thatch levels
  • Place your turf facility on a regular aeration program – this will reduce the compaction, provide a good amount of air into the profile, reduce thatch, and provide a easy avenue for roots to grow deep chasing water. Rotate the types of aeration you apply to your surface, there are no bad types of aeration generally speaking
  • Avoid excessive applications of Nitrogen  – not only does this lead to excessive thatch accumulation, excessive applications of N also leads to carbohydrate exhaustion. When an excessive application of N is given to the plant all available carbohydrate reserves get mobilized from the root system to the leaf & stem of the plant to deal with excessive application of Nitrogen. This exhausts the carbohydrate reserves and the root system ultimately suffers as its the lowest priority of the plant. Nitrogen is required in measured amounts in order to help the root system to develop, following the ‘little & often’ rule.
  • Balance soil nutrients, particularly phosphorus and potassium. Both these nutrients are closely associated to root growth. As we know that root growth is at its strongest in spring and leading into summer so it is important that phosphorus and potassium levels are good at least during this period.
  • Adding the plant hormone Auxin to the nutrition program can assist in the development & maintenance of the root system – another benefit of this practice is it can reduce the fabrication of cytokinin, which can naturally balance out the hormone balance giving more priority to the root system
  • Avoid scalping from mowing. Observing the 1/3 rule (ensuring that never any more than 1/3 of the plant’s length is removed in any one mowing) is crucial in ensuring that the progress of the root system is not hindered. As soon as there is any damage to the turf surface, the root system is the first to suffer as it’s required to assist with the repair of the damage. This is particularly the case when the turf is scalped with the mower – the plant will mobilize nutrients and carbohydrates from the root system first to repair the damage in the shoots. A secondary draw back of scalping is it reduces the amount of foliage that the plant has available to take in sunlight for the photosynthesis process – it is the leaves and stems that take in sunlight, scalping suddenly removes this foliage.
  • Avoid stresses during spring where possible, especially for cool season grasses when root growth is at its greatest, particularly herbicides during this time
  • Consider using Primo maxx in the maintenance program – it has the potential to redirect the plant nutrients into the root system to aid development

References Sited

Melbourne Polytechnic Diploma Manage Plant Cultural Practices Unit Notes

 

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