Managing Water in Soil

By Demie Moore in Consultancy on 9th Jun 2008 15:00

Professional turf managers the world over agree that producing a consistent, firm (not soft or hard) surface with good grass coverage is their aim. While many factors go into this, one of the most fundamental is management of moisture in the rootzone. This will not be earth shattering news for readers. What may be news to some, however, is the role that soil surfactants can play beyond helping with dry patch. In combination with good drainage and cultivation practices, soil surfactants can help manage water in the soil where it is most important; the rootzone.

It is general knowledge that consistent and desirable levels of water and air are required in the rootzone to achieve healthy turf and firm surfaces, and that these are affected by drainage, soil compaction, and drought. Many factors come to play that work against the realisation of those desirable rootzone conditions that are needed to produce good quality sporting surfaces.

A few that have a huge impact, and are beyond the direct control of the turf manager, are weather – especially very wet or very dry conditions – natural changes in the soil environment and the use of the playing surfaces which is, after all, their ultimate purpose. While turf managers have not yet achieved the ability to control Mother Nature and the users of their facilities, they do have tools and practices available to manage the consequences.

A common factor of the consequences of weather, change in the soil environment and use is their negative impact on soil moisture relations and the turf’s growing environment. Poor drainage, which can be caused by and contribute to compaction, is perhaps the biggest headache to many sports turf managers.

Of course the wet conditions accompanying poor drainage create soft surfaces that are, at least, messy if not unplayable, and also contribute to increased likelihood of disease and its associated turf damage. Compaction, resulting from foot traffic, especially when soils are wet, inhibits good turf growth and, when things dry out, results in surfaces that are too hard and interfere with play or increase potential for injury. And soil water repellency and other natural changes in the rootzone environment interfere with water movement into and through the soil, further confounding the soil moisture conditions and the ability of turf to grow uniformly. Addressing what is going on with water in the soil is key to getting turf, and the sporting surface, back on track.

Where to start?

Evaluate the situation at hand. If there are evident problems, determine what and where they are and why they are occurring. “Prescription without diagnosis is malpractice”. This phrase is as applicable in our industry as it is in medicine and many other areas to which it can be applied. So, before launching into any practice or programme, first taking stock is a good idea. This is equally valuable, maybe even best, when things are going well, before problems are apparent. Identifying causes of problems, or potential problems, is an important part of the diagnosis in order to select the most effective management practices.

Good drainage is vital for achieving desirable levels of air and water in the rootzone. However, there are various factors that can contribute to drainage problems which, if they are not all recognised and addressed, may cause corrective efforts to fall short of their desired effect. Things to investigate include where does the drainage problem begin? How deep does it go? What are the causes? Is present drainage adequate and working? If not, why not?

Answers to these questions will help determine if a full scale drainage installation project will be needed, or be sufficient, or if some other actions from cultivation are needed such as cultivation to open the surface, use of soil surfactants for uniform movement of the water into and through the soil profile, or changes in land features outside the particular area. Achieving good drainage may require more than the installation of physical drainage.

Compaction is also pretty inevitable where there is a lot of use. So, the more practical goal may be managing it more than really trying to prevent it. Compaction effects turf growth and surface hardness and needs to be considered in order to develop effective management practices.

Cultivation practices such as aeration, spiking, managing the height of cut, topdressing etc. are, of course, essential. Soil surfactants promote uniform and desirable moisture conditions in the soil which can also help delay, or slow, compaction as well as benefit cultivation practices. Soil moisture levels affect, and are affected by, compaction and, therefore, are key to managing compaction as well.

In addition to drainage and compaction challenges, conditions in the soil and growing environment change over time and vary throughout a season. Being aware of these changes, and managing them to achieve your desired rootzone conditions, is ongoing and may need to change over time as well. How soils accept and transport water (soil hydrology) is one of the key things that changes. Naturally occurring populations and processes within the soil, from organisms to roots, are dynamic and cause changes in the physical conditions and functioning of the soil and growing environment.

Two examples of changes in the rootzone environment that have major impacts on the water and air conditions in the soil are water repellency and plugging of pores. It is important to investigate how much these, and other such factors, are at play in your soil and plan your management programme accordingly. Where water repellency is present in soil and/or the thatch mat layer (which you can test for by placing drops of water along a dry-ish soil core and seeing if there is a delay in their penetration) soil surfactants are the only way to truly restore wettability.

Where other changes, such as plugging of pores, have developed a thorough physical soil analysis is the best way to determine the current status and probable causes of problems. Cultivation and topdressing, in combination with a surfactant programme, may be required to provide consistent dispersion of water in the soil. The bottom line here is that soil conditions change. It’s unavoidable, so managing internal soil conditions is key to producing quality turf and playing conditions.

Poor drainage, compaction and changes in the soil all relate to water in the soil and to the conditions necessary for good turf growth and firm sporting surfaces. Physical drainage, cultivation practices and topdressing/soil modification are acknowledged management practices to deal with these problems.
Soil surfactants are often not considered except for dry patch problems. However, it is a myth that surfactants are only good for dry patch.

Surfactants certainly help with dry patch, but that is just one symptom they relieve. In order to have uniform turf, you must have uniform rootzone conditions, and this is where surfactants are most effective because they allow water to move more easily into, and through, most soils and their use is complementary to other practices. Soil surfactants “complete” the management of water in the soil by working in concert with and “between” the more physical practices of cultivation and drainage systems.

Choosing the right soil surfactant depends on things like need at hand, the track record for a particular surfactant, the facility’s budget etc. Different soil surfactant formulations have different performance characteristics, and really are not all the same.

A publication is in the works at the STRI which will identify many of the characteristics of the various soil surfactants currently available in the UK market and will provide some useful information. In addition, to avoid pouring money down the drain, it is always important to require some proof of performance before purchasing a product. Misleading, unfounded statements are, unfortunately, out there as the surfactant market is not regulated like fertilisers and pesticides. As a buyer, beware!

Today many turf managers spend hundreds or thousands of £’s to hire aeration equipment in an effort to improve the soil environment, increasing air and water movement. However, while aeration may provide vertical entry points for water into a soil environment, it typically only affects about 5% of the surface. Therefore, movement of water into the remainder is a significant factor in the success of such aeration programmes.

Even low levels of soil water repellency can hinder. A good quality soil penetrant, such as Aquatrols Dispatch, applied monthly during the growing season at a rate 4 litres per hectare, can cost as little as £ 29.72 per hectare per month. This product has been shown to increase infiltration and reduce runoff by 20-50%, thus offering water and energy savings. In many cases, these savings quickly surpass the cost of the surfactant.

With the increasing costs of products such as fertilisers and pesticides, efficient use of them is very important. Getting water and the applied products where they need to go is a key part of this. Having fertiliser and applied products carried off-site with run-off water is not only costly but can be damaging to the environment. Aquatrols has the results of university testing which demonstrate that surfactants have a positive effect on the delivery of fertilisers and other materials to the soil as well. These research findings are available to interested turf managers.

Improved turfgrass quality, water savings, lower energy costs, increased fertiliser efficiency, more uniform establishment of new swards and a more uniform playing surface are the goal of every turf manager.

While turf managers cannot control the weather or prevent the wear and tear of everyday use of sports surfaces, surfactants, along with other good management practices, can help gain and maintain control over the status of the water in your soil and the quality and durability of your turf surfaces.

Further information from Demie Moore, Corporate Relations, Aquatrols