Skip to content

Water Content helps Turf Growers find Water/Nutrient Balance

Many athletes don’t like artificial turf. They say it’s hot, uncomfortable to run on, causes burns when you slide or fall on it, and changes the way a ball moves.  Professional women’s soccer players even started a lawsuit over FIFA’s decision to use artificial turf in the 2015 Women’s World Cup.

Soccer players running after the soccer ball on a green field

Soccer players on natural turf.

Some universities—including Brigham Young University—have responded to athlete concerns by using natural turf fields for practice and in their stadiums. But the challenge is to develop plants and management practices for natural turf that help it stand up to frequent use and allow it to perform well even during the difficult fall months. It’s a perfect research opportunity.

BYU turf professor and manager of BYU sports turf, Bryan Hopkins and his colleagues in the Plant and Wildlife Department, have been able to set up a new state-of-the-art facility to study plants and soil in both greenhouse and natural conditions. The facility includes a large section of residential and stadium turfgrass.  

Before Soil Sensors

Initially, BYU maintained the turf farm grass on a standard, timer-based irrigation control system, but over time they realized that understanding the performance of their turf relative to moisture content and nutrient load is crucial. Last year during Memorial Day weekend their turf farm irrigation system stopped working when no one was around to notice.  During those four days temperatures rose to 40 C (100 F), and the grass in the field slipped into dormancy due to heat stress. In response, Dr. Hopkins began imagining a system of soil moisture sensors to constantly monitor the performance of the turf grass.  He wanted not only to make sure the turf never died but also to really understand the elements of stress so they could do a better job growing healthy turf.

Sensors Give a Clear Picture

Soon afterward, a team of scientists, including fellow professor Dr. Neil Hansen, installed volumetric water content (VWC) and matric potential sensors at two different sites: one in the sports turf and one in a residential turf plot.  Each plot had two installations of sensors at 6 cm and 15 cm, along with VWC only at 25 cm, to measure water moving beyond the root zone. Combining these measurements, they could clearly see when the grass was reaching stress conditions and how quickly the turf went from the beginning of stress (in terms of water content and time) to permanent wilting point. In addition, ancillary measurements of temperature and electrical conductivity provide an opportunity for modeling surface and root zone temperature as well as fertilizer concentration dynamics.

Researcher digging a dirt canal and installing sensors

Installing water content sensors at the BYU turf farm.

Errors Revealed

What the researchers learned was that they were using too much water. Dr. Colin Campbell, a METER research scientist who worked with BYU on sensor installation, comments, “We found in the first year that the plants never got stressed at all. So this year, the researchers allowed the water potential (WP) at 6 cm to drop into the stress range (~ -500 kPa) while observing WP at 15 cm (-50 kPa to -60 kPa). We hope this approach will reduce irrigation inputs while creating some stress in the grass in order to push the roots deeper.”

What’s happening with the water?

Dr. Campbell’s favorite part of the sensor data was the detailed picture it gave of what was happening with the water in the sandy soil (Figure 1). He says, “Most people believe that they have an intuitive feel for water availability in soil.  If we were only using water content sensors, seeing a typical value of 20% would lead us to believe we were comfortably in the middle of the plant available range (A).  But in this study, using our colocated soil water content and soil water potential sensors, the data showed readings over 15% VWC were too wet to affect the WP (B). However, once WP visibly changed, it quickly moved toward critical stress levels (C, -1500 kPa is permanent wilting point); it only took two days for the water potential to change from -8 kPa to -1000 kPa.  A subsequent dry period (D) shows similar behavior, but this time the 15 cm WP drops to near -1000 kPa.”

Water potential changes diagram

Figure 1

The plant stress levels were reached surprisingly quickly in this soil because its sand composition has a lot of large pores and not very many small ones (Figure 2). Campbell explains, “The large pores store water that is not held tightly due to low surface area, so the water is freely available. But at around 10% VWC all the water from the large pores is used up. As the soil dries beyond that, the water is held tightly in small pores and becomes increasingly unavailable. This is clear in the moisture release curve.  We see almost no change in water potential as the soil dried to 16% VWC, but from 10% down to 7%, the water potential reached permanent wilting point, and it happened in just over a day.”

VWC and Water potential sensors diagram

Figure 2

What the Future Holds:

The researchers wanted to make sure that if they went down to certain stress levels, they wouldn’t cause harm to the plants, so this year, they installed a weather station to monitor evapotranspiration and calculate irrigation application rates.  They also began measuring spectral reflectance to monitor changes in leaf area (NDVI) and photosynthesis (PRI).  This will enable them to see the impact on the plants as the turf is drying down.  “In the future,” says Campbell, “we hope that both commercial and residential turf growers will be able to more effectively control their irrigation and nutrients based on what we find in this study.”

Download the “Researcher’s complete guide to water potential”—>

Download the “Researcher’s complete guide to soil moisture”—>

Get more information on applied environmental research in our

31 Comments Post a comment

Trackbacks & Pingbacks

  1. Water Potential/Water Content:  When to Use Dual Measurements
  2. Which Factors Make Rain Gardens More Effective? - Environmental Biophysics
  3. Improving Drought Tolerance in Soybean - Environmental Biophysics
  4. Building a Martian: the University Rover Challenge - Environmental Biophysics
  5. Does Early Planting Increase Risk to Winter Canola? - Environmental Biophysics
  6. Green Roofs — Do They Work? (Part II) - Environmental Biophysics
  7. Green Roofs-Do They Work? - Environmental Biophysics
  8. Can Wastewater Save The United Arab Emirates’ Groundwater? - Environmental Biophysics
  9. Irrigation and Climate Impacts to the Water-Energy Balance of the WI Central Sands (Part I) - Environmental Biophysics
  10. Using The Salt Balance Approach to Measure Soil Drainage - Environmental Biophysics
  11. Will Sample Disturbance Lead to Lower Accuracy?
  12. Screening for Drought Tolerance
  13. Measuring Moisture in Concrete
  14. Measuring Frozen Water Potential: How and Why?
  15. Convincing Growers to help the Environment
  16. New Medium Scale Soil Moisture Measurement Technique
  17. Water Potential Versus Water Content
  18. This Idea Must Die: Using Filter Paper Method as a Standard
  19. Do the Standards for Field Capacity and Permanent Wilting Point Need to Be Reexamined?
  20. Double Ring Infiltrometers versus DualHead Infiltrometers
  21. The Right Auger for Water Content Sensor Installation
  22. What does SMAP mean for in situ soil water content measurement?
  23. Water Content Innovation Involves Growing Pains
  24. Are Arduinos Practical and Cost Effective for Science?
  25. Modeling Available Soil Moisture
  26. Despite Drawbacks scientific collaboration pays off
  27. TDR versus Capacitance or FDR
  28. Volumetric Water Content: Keeping your Eye on the Goal
  29. Soil Moisture Sensors in Trees - Environmental Biophysics
  30. JAR-Measuring Forest Litter Moisture Content - Environmental Biophysics
  31. Data Don't Lie - Environmental Biophysics

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.

Share to...