Outdoor Services Crew

Thursday, October 25, 2012

Turfgaurd Sensors

Over the past few years a new tool has come around for the Turf Industry and after letting things mature a bit I have moved forward in deploying this technology here at CU. It is called Turfgaurd and is a soil moisture, temperature, and salinity monitoring tool that will help us monitor the soil profile directly. The system is wireless and uses the backbone of our current Network 8000 Central control system.

There are two pieces to the system, one is the soil probe itself that is inserted into the ground and the other is a small radio transceiver that is mounted inside our current VP controlers and draws power from the controller for operation. There is a small base station in the Turf Office that receives the signal and is viewed through the Sitevision software on the computer in the office. The main display screen, seen above, shows a quick overview of the readings of each of the sensors. Currently we have 9 sensors deployed in locations throughout campus. The main display screen shows soil moisture (top) soil temperature (middle) and the soil salinity(bottom) in a easy to see quick glance.

The soil sensors themselves are self contained and have a battery life of about 3 years. They have an in-ground range of about 500' to reach a transceiver. There are 6 probes on each sensor, 3 on top and 3 probes 5" below.

In the picture above you can see the upper set of probes and the lower set of probes. Each probe is responsible for a different reading. The install is pretty easy.  We used a golf course cup cutter to create a clean hole so the sensor can be inserted into undisturbed soil. We chose to place the upper probes at a depth of 2 inches from the top of the soil profile. We recieve readings at 2" and 7" depth in the soil profile.

In the pictures above you can see the sequence of the installation. The cup cutter makes the perfect hole to insert the device into as well as provides us a clean sod plug to put back on top when we are finished. Once the hole is cut to the proper depth to put the top probes at 2" below the soil surface, the probe is then pushed into the side of the hole into the undisturbed soil profile to ensure good tight contact with the soil profile. To make sure we were able to find them we took exact measurements to triangulate the location of each sensor as well as put a large metal washer on the top of the sensor allowing us to use a metal detector to pin-point their exact location.

The real power of the system though is in the data monitoring. I am able to pull up the individual sensors in the field and look closer at the data and determine the profile situation.
In this graph you see two colors, these represent two different sensors. Both of these sensors were placed on Franklin Field. The yellow line is the center of the field where we have decent soil and the orange line is the north section of the field where we have major challenges with the soil profile. You can clearly see the top graph shows that on the 16 of October we ran an irrigation cycle.  You can clearly see the spike in the graph representing the applied moisture as it reached the 2" depth. We have always known that the north end of the field holds moisture and does not drain very well at all.  This graph clearly represents our past knowledge from a scientific perspective. You can see that the yellow line is showing the moisture moving through the profile at a quicker rate than the orange line, thus showing the profile drying quicker. Then at the end of the line you can start to see the moisture increase from the rain snow mix we just recieved.

This graph represents two sensors we have deployed on Farrand Field. One sensor(orange) is in the center of the field where we have the Quickdrain drainage system and the other sensor(green) is in the west end of the field outside of the drainage system. Again as we have always known the drainage system works great at allowing moisture to pass through the profile. This shows how much faster the drainage system prevents standing water on the main field portion. You can see a spike on the orange sensor which shows an irrigation cycle we ran on the field, the green represents the non-drainage portion of the field which we did not water because the soil holds moisture and there was not a need to irrigate that portion.

As you know, CU is a very compact campus which provides many challenges. One major challenge is parking on campus, especially during large campus events. The first priority of the recreation fields is to provide a safe playing field for all the rec sports that are played on them.  Secondary uses include events and in some cases parking cars on the fields for even larger events.  During large events there are times when mother nature does not cooperate with event plans.  At those times the decision is made based on in-the-field inspection as well as the Turf Crew's knowledge of what moisture level is safe to allow cars to park on the fields and not damage the fields. Obviously when the decision is made to close parking for an event there are impacts to all facets of the event. This includes dissapointment with not being able to park directly on campus for whatever event you may be attending.  Inevitably there are questions about the necessity of the closure. This new system will help greatly with providing scientific data to help support the Turf Crew's knowledge and experience with the ability of the field to handle each specific type of event and if the field condition is right for the type of usage.

Recently there was a need to close the field for parking for an event. In the top picture you can see that our soil moisture level was at 46.6% at the time parking was supposed to begin. The biggest challenge for the turf crew is not evaluating the field for foot traffic, that is easy.  The real challenge comes with knowing that vehicles can greatly vary in weight compaired to human traffic and you could have vehicles weighing from 2,000lbs to large SUV's weighing up to 6-7,000lbs.  This will dramatically increase the need for the soil profile to be at the proper moisture level to be able to resist these kind of forces without altering the grade of the field.  In the second picture above you can see the field soil moisture was much lower 37.09% at the time for another field parking event.  That may not seem like much of a drop in percentage but the field condition was much improved and we were able to allow parking for an event on that day.  The field was noticeably dryer but it was still not in the ideal condition.  But that is where the human factor plays the biggest roll in the decision, for the turf staff to know, from years of experience with field parking, what the "feel" under the foot is makes a huge difference.  Just relying on the data is not enough for these decisions.  Remember that the moisture reading is from 2" below the surface and depending on the recent temperatures you could still have the surface of the soil very soft, but if it has been warm and dry the surface could be acceptable for parking.

This is going to be a great tool in the tool bag to help support the knowledge and decison of the turf staff with scientific data. As we have these systems longer we will continue to learn what a % moisture content truly is like in the field and this will help us to gauge the proper uses of the field and what damage is received from the different types of events at that moisture level.

Finally, this graph represents a sensor we have on Benson Field. What is really interesting is the data helps to show that our "in the field" decisions of when to water have been pretty close. If you notice the "dry down" level is very close to when we then make an irrigaiton application in each instance of watering. This time of year, as we are stretching water for root developement, we are averaging every 5-7 days for a cycle. What is interesting is we have started testing the limits a bit with our "dry down". You can see in the graph where we let the moisture level drop much further than the previous times we would make an application. The part we are trying to learn is based on our root structure, how low on soil moisture can we go before the turf starts to stress. You can see we stretched the moisture level out  futher and found that in this location we can go longer than we thought based on visual determination. As you can see we threw a large amount of water to replenish from the dry down.

We will continue to deploy more sensors as funds become available and continue to refine our irrigation practices even further with the use of this new tool.