Turf Management and Soil Moisture Monitoring

Soil moisture sensors have been around for a long time. Turf managers have used soil moisture monitoring, apparently with limited success. Why has this been the case? There are a number of reasons for this.

Incorrect installation, poor site selection, lack of data interpretation, poor technical and agronomic support. Soil moisture sensors are a tool to assist with management decisions. If sensors are installed incorrectly, installed in the wrong locations, not ma  intained and the data collected can not be understood by managers, the successful use of the technology is limited and unlikely.

Industry turf professionals and council turf managers are now beginning to use soil moisture sensors and monitoring in order to achieve real savings and benefits. The philosophies of soil moisture monitoring and its successful implementation in horticultural industries is now being used in turf applications.

It’s not just about installing a sensor with the irrigation system and then walking away. There are fundamental steps in the process to ensure that the technology is of real value to users:

• Selection of the most appropriate sensor.
• Auditing the entire irrigation system to identify any problems that will affect efficient water delivery.
• Selection of the most representative location for the sensor; soil type and within the effective wetting area of the irrigation system.
• Installing the sensor at the correct depth, within the active root zone of the turf.
• Data interpretation so managers are able to understand the data being collected.
• Calibration of sensors through in field site inspections and core sampling to ensure the data being collected relates to the actual conditions in the field.

The Current Situation.

Presently, most consideration given to the selection of an irrigation control system is based on what amount of control can be exercised without getting off the seat in front of a computer or the ability to control valves from a distant point. The most important consideration is generally an add on of determining the water need of the plant and once that need is reached, how much irrigation is required. Most companies who manufacture controlling systems are promoting the use of weather stations for this purpose and Dr. Bob Carrow’s work from Georgia has highlighted the inherent weaknesses of systems that only rely on weather station data. For more precise and accurate data derived from actual soil moisture, Carrow has found that soil moisture sensors are a valuable instrument. In addition to this, Phil Ford, senior lecturer at NMIT in Melbourne, has conducted measurements on the water use of a number of turfgrass varieties. His work draws serious questions about the crop factors used when weather station data is the determining factor for irrigation scheduling. These crop factors are changing on a daily basis and often these changes are considerable but no allowance is made for this phenomenon within the calculations used.

So what is the ultimate aim of turf managers when considering irrigation management?

• Consistent good quality turf and playing surfaces?
• More efficient water management?
• Reducing labour costs?
• Accountability to rate payers or club members?

In order to achieve the above results there must be a link between the data collected and the management of the irrigation. An efficient solution is now available that does not require the capital investment for central control systems. The process is simple. Taking the above factors into account with regards to collecting good data is the first step. The next step is providing a simple interface between the data and the control of irrigation, based on the amount of moisture within the root zone of the turf.

“At Frankston we have a larger number of sand based grounds where monitoring moisture content is critical. Using the sensors and working to improve our water use has paid dividends in reducing our need to “water to be sure” and has provided indicators to other irrigation system and soil condition related issues to be rectified as well. Visitation to reserves has been reduced except where issues need to be addressed, leaving staff to concentrate on other work. We have relied on the sensors to provide the data for interpretation at the start of the day when work programs are being formulated. The data provided is instantaneous and locally relevant, ie we are not relying on remote data being extrapolated without regard for variations in local conditions and the water use is being reduced without guesswork risking the survival of the playing surfaces”.

An iNTELLiTROL monitoring and control system installed at Frankston. 20 sites are installed, monitoring and automating irrigation events. The soil moisture data is automatically sent to a dedicated web site for the council, where managers are able to view live data, check the status of each site and remotely adjust irrigation set points from any PC with internet access. Alarms are sent via SMS or email when conditions are out of range or there are problems with the irrigation system, such as high or low flow or pressure.

The method

• Correct installation of the soil moisture sensor.
• Collection of the data.
• Establishment of optimum soil moisture levels through data interpretation and in field inspections of the turf and soil.

Linking the data to the time based controllers in order to automate irrigation based upon such factors as:

• The soil water holding capacity.
• The rate of water use by the turf.
• Prevailing weather conditions.
• The effectiveness of irrigation events.
• The effectiveness of rain events.
• Times when turf can not be irrigated due to sporting or other ground commitments.

Correct soil moisture monitoring is identifying many inadequacies with irrigation management practices. Apart from the uniform application of water, one of the obvious problems is incorrect volumes of water being applied to sufficiently wet the root zone of the turf. In most cases, irrigation durations have been increased from 20 minutes to between 45 minutes and an hour; based upon the soil type. The aim is to apply sufficient water in order to replenish the soil moisture within the root zone of the turf, not just replacing evaporation.

The principle is to fill the root zone of the turf and then turn off irrigation until the soil profile has dried to a predetermined point. Small, regular top up irrigation events do not promote healthy turf or strong vigorous, healthy drought tolerant roots.

Some council’s have produced significant water savings through the use of this technology during the summer months. Others are tending to use similar volumes of water; however their water use efficiencies have increased. For example, rather than three nights of irrigation with 20 minute cycles, one night with a one hour cycle refills the soil profile, rather than simply replacing evaporation. One council reported savings of approximately 250,000 litres over a 6 week period (on one oval), using soil moisture monitoring combined with the iNTELLiTROL system, while still improving turf quality.

It’s not rocket science

• Sensors are connected to a data logging and control board.
• The data from the sensor is analysed, in conjunction with field inspections.
• Upper (full point) and lower (refill point) moisture levels are determined and then programmed into the board, which is located next to the time based irrigation controller.
• The time based controller is then programmed for irrigation dates and run times.
• The data logging and control board is then wired to the time based controller.
• Irrigation events will occur when the soil moisture reaches the dry set point and disabled once the soil moisture has reached the upper, or full point.

“We at Hobsons Bay have found the system to be a cost effective and reliable control system that ensures the irrigation operates only when the turf needs it (ie. irrigation system operates only when the soil moisture level dries out to a predetermined point). We have found the condition of our turf surface has increased dramatically primarily as a result of your system as we are not overwatering or underwatering as had been occurring in the past. Council staff have no need to intervene in the system and it has proven to be almost a set and forget control system that is operating above our expectations”.

Data from Western Australia. The black line shows soil moisture levels in the active root zone of the turf. The pink line displays soil temperature. Blue zone too wet. Red zone too dry. Green zone optimum.

Case Study – Ipswich City Council

Conclusion from Active Playing Surface Pilot Program – Soil Moisture and Turf Performance
Geoff Faulkner

Water efficiency is becoming more important due to water restrictions continuing at level 6 and will have permanent restrictions in the long term and the cost of water is set to rise. Ipswich City Council is committed to continuously improve and adapt new water saving techniques and management practices.

As part of ICC Water Contingency Plan – a number of water end uses (demand) have been identified in order to establish the various water sources and quality available (supply). The investigation of various smart technology such as soil moisture, rain switches, flow meters, and central controlled systems on all ICC managed sports fields are part of this contingency planning.

Even with the limitation of the relatively short period of the pilot and the welcome ‘complication’ of good rainfall, the permanent in-ground, web enabled system has demonstrated its capacity to be an excellent platform from which to manage and fine tune irrigation management on sporting fields.

Further expansion of the system and fine tuning will provide additional water savings. Based on the massive savings demonstrated in the pilot, this system would potentially deliver massive water savings should it be applied across SEQ. Any system can only perform to its capability when the managers have a passion and desire to fully use the system. ICC field staff have been crucial in the implementation of the systems and the authors gratefully acknowledge and thank all involved in collecting and analysing data to produce this report.

Saving water can be easy; you simply don’t irrigate. This option is however not valid. The ultimate aim is to use the water resource as efficiently and effectively as possible to achieve the desired outcomes; consistent, uniform, good quality turf and fit for use playing conditions.

Councils throughout Australia are beginning to implement water management plans that are taking into consideration a number of factors such as:

• Prioritising water allocations to higher profile sites.
• Auditing irrigation systems to identify problems, so that optimum irrigation efficiency is achieved; getting the optimum results from water applied.
• Moving water away from sites where the irrigation systems are operating poorly. For example, there is little value in irrigating an oval where the distribution uniformity of the irrigation system is 40%. This is simply wasting water as the same volume of water is being applied, whether the irrigation system is uniform or not, however the end result with an inefficient irrigation system is poor turf quality and uniformity.
• Changing over to warm season turf varieties.

Using iNTELLiTROL during times of water restrictions

Despite the fact that many councils are restricted to when they are able to irrigate, iNTELLiTROL can assist with water management. Firstly, by monitoring soil moisture conditions within and below the root zone of the turf, managers are able to measure the effectiveness of irrigation events, as well as monitor the depth and rate of water use. The data from the sensors can also provide managers with valuable information on the effectiveness of rain events.

Irrigation management during Spring and Autumn months can also be tricky where weather patterns can be variable. With iNTELLiTROL installed, irrigation is managed using the data and automation of the system on a day to day basis; no guess work.

Where there are restrictions on irrigating, the principle of iNTELLiTROL is the same. Program the irrigation system to operate during the allocated periods, for the optimum run time. With iNTELLiTROL installed, with the correct full and refill points programmed, the irrigation events will be enabled if the moisture has dried to the low set point. After the irrigation event, presuming adequate water was applied to fill the profile, further irrigation events will be disabled until the soil moisture has dried back to the refill point. In the situation where insufficient water is being applied to fill the profile back to full point when irrigating, therefore irrigation events are enabled when programmed, iNTELLiTROL will save water during periods of rain and cooler weather.

Soil moisture monitoring for improved water management does work. It is being successfully used by an increasing number of turf managers. With the correct selection of sensors, installed correctly with technical and agronomic support, real water savings, improved turf quality and labour reductions are being realised.