The science
Thirty years of turfgrass science research and experience sits behind every number TOMi™ reports. This is the short version as to why it measures what it measures, where it measures, and how many samples a surface needs to give you the insight you need.
Moisture
Moisture is the single most influential lever in turf performance — and the one most often improperly managed or measured incorrectly. What matters is not how much water is present, but how much of it the turf can actually use, and how much air is there beside it.
At optimum moisture, there is a range of approximately 8% (Optimum ±4%) of moisture that is usable by the turf. Below this range, much of the water in the rootzone is unavailable at any time: sequestered, trapped, or simply out of reach of roots. At the other end, an abundance of water is no help either as it takes up valuable space that should be occupied by oxygen, leading to dysfunctional key physiological processes the turf needs to perform and reach or exceed expectations. And simply put, water is wasted which is a sin for anyone in our profession.
Using TOMi™ to find the optimum condition for your turf and managing conditions to within the usable range of healthy water/air balance positively improves EVERYTHING.
We believe a number without this context is worthless, and why a reading taken without this insight may well be worse than no reading at all.
| VWC | Behaves like |
|---|---|
| 0 – 8.5% | Sand |
| 8.5 – 10.5% | Loamy sand |
| 10.5 – 12.5% | Sandy loam |
| 12.5 – 15.0% | Silt loam |
| 15.0 – 18.0% | Silt |
| 18.0 – 23.9% | Loam |
| 23.9 – 27.5% | Sandy clay loam |
| 27.5 – 32.5% | Clay loam |
| 32.5 – 36.0% | Silty clay loam |
| 36.0 – 38.5% | Sandy clay |
| 38.5 – 40.5% | Silty clay |
| > 40.5% | Clay |
It is not only soil particle percentages that determine the physical — and chemical — qualities of your rootzone. The behavior you actually manage is the one in this column.
The 8% fine line
Avoid large deltas that exceed the critical 8% range. While this number may vary a bit lower or higher depending on rootzone water holding capacities, do NOT underestimate the negative effects of managing water outside of this range around your optimum. Otherwise, the turf is not being trained but rather gets used to an abundance of water, reducing its natural stress defenses against an abundance of stressors. Even disease pathogenic fungi respond favorably to the conditions that are unfavorable to turf.
Dr. Magro’s research and disease predictability models clearly have shown correlations with effects of disease directly related to the deltas of water conditions from day to day. Fairy ring, for instance, LOVES large variations in turfgrass moisture conditions. Great reductions in the appearance of Fairy ring on the surface have been realized just by managing the moisture closer to an optimum water/air balance on a regular basis.
Irrigation decisions made on minutes rather than measured conditions are risky at best. Further, moisture on the surface is no indication of water where it matters, in the optimum rootzone depth where the dominant exchange occurs, the upper 6 cm. So, use TOMi™ and irrigate to what your turf is telling you.
Beyond texture, rootzone structure is constantly manipulated by our actions, chemistry and by nature. Turf naturally adds 18–24% or more ‘stuff’ to the rootzone every growing season. With mismanagement of water/air balance, microscopic layers begin to form, compressing this ‘stuff’ and leading to excessive water holding properties that are very detrimental to turf. The ONLY way to see these changes occurring BEFORE symptoms show up is to monitor PROPERLY.
With so many variables acting on turf, seeing the not-so-obvious — the change before the symptom — is what makes a significant improvement to any turfgrass management program.
Turfgrass fact: The properties of the turfgrass rootzone, when not managed best, will hold water against the pull of ET (making this measurement irrelevant) AND against the downward gravitational movement of the rootzone, leading to greater losses in available air, and significantly decreasing the turf’s natural ability to perform or withstand stressors.
Depth
The influence of the turfgrass upper 6 cm of rootzone dominates the water and nutrient exchange versus anywhere else in the profile or any other section of the rootzone (Magro, Macolino, Fidanza et al., 2025).
Scientifically proven from field and laboratory research led by Dr Carmen Magro and international turfgrass scientists indicated specifically that the upper 6 cm of the rootzone dominates both moisture and salinity exchanges to the turf and has the most significant influence on surface conditions. More importantly, it is the bulk measurement of this precise region that indicates effective feedback from turf to make better watering, nutrient and cultural practice inputs.
Research showed the validity of the 6 cm depth through ALL rootzone soil types and ALL turfgrass types whether C3 or C4 turf, no matter how deep the roots were.
Sampling shallower than this by any amount misses the bulk activity of water/salinity responses while sampling more deeply simply dilutes the sample result away from the most influential region, and this leads to missing vital information about your turf before problems show their ugly faces.
A practical understanding of the rootzone system, and the measurement taken in the area that tells us the most about the entire turfgrass system is the difference between taking data and getting PURE Insight™ to your turf’s condition.
Sampling
Industry pioneering research work done by Dr Carmen Magro et al. clearly identified the minimum number of samples that leads to truly understanding a turf system, giving precise information to understanding moisture, EC, salinity or nutrient needs/influences, and temperature. Using standard error of the mean, measuring 1 to 81 samples in small 1 m² plots clearly found a number to follow and what is now the industry standard, prompting the need for advanced measurement technology now only found in TOMi™.
That is the practical rule science shows for lowest cut turf. However, as turf height of cut (HOC) rises, fewer samples can be taken to achieve the same statistically viable results. Not meeting a minimum sample rate may well be wasted time for yourself and staff, and increasing sample rate may have some added benefit, but the returns diminish when examining time versus value of info.
A poor sample pattern that is not randomly spaced, no matter what the sample count is, will produce a false analysis. Similarly, a poor sample count on a perfectly randomized pattern too will produce a false analysis. These 2 factors go hand in hand.
Consistent, vertical insertion of TOMi™, with a representative minimum number of samples on a consistently spaced pattern, to its full 6 cm depth is what makes one analysis comparable to others — today, next week, and next season.
Distribution uniformity
Distribution uniformity (DULQ), known as Distribution Uniformity Lower Quartile analysis, has been an industry best-practice measure since the 1990s: the average of the lowest 25% of catch cans divided by the average of all catch cans, times 100. Carmen Magro adopted it into spatial analysis for turfgrass systems in 2005.
But a catch can DU tells you the distribution of the sprinklers, not the moisture as the turfgrass sees it, and moisture on the surface is NO indication of moisture beneath the surface. In a study where moisture in the turf was measured 12 hours before irrigation, moments before irrigation, moments after irrigation and 12 hours later, at no time did the DU (spatial analysis of moisture) from the catch can analysis resemble the DU in the turf. However, a slight spatial analysis correlation occurred only in the measurement just after irrigation. This was likely due to the fact that the technology used (pre-TOMi™) had below-ground moisture skewed due to its inability to separate the above-ground moisture from its sensing processes.
What we learned: There was no relationship between moisture in the catch cans versus moisture in the turf. Managing moisture from the perspective of the turf (what is in the active 6 cm bulk depth) will significantly improve your operation almost instantly, while chasing catch can analysis results may well leave you in worse condition. Use catch can analysis to improve your sprinkler delivery. Use TOMi™ spatial analysis to improve your runtime/pressure/nozzle setup at each station.
Kriging — a geostatistical method dating to Danie Krige’s 1951 work in South African mining — is now available in many mapping tools. Be mindful of the origin of the data and the methods used to interpolate it.
Salinity & temperature
Electrical conductivity measures any ion, positive or negative, in the rootzone solution — which means it is directly related to nutritional ions (good salts) as well as bad salts. Elements vary in size and in activity, with bad salts having a higher influence (per ppm) on EC than good salts. TOMi™ not only measures total EC activity. It assesses salinity stress, which is highly indicative of bad salt activity or ‘stagnant’ salts in your system (impacted by hindered drainage and capillary action), prompting you to do something about it ahead of problematic symptoms.
Water quality has a direct, daily impact on EC activity. Know your water quality, and more importantly, how to manage it. And remember the practical conclusion: manage your moisture and you can manage any level of salinity. Train your turf by understanding your limits and influences before symptoms occur.
Want to know what salts are influencing your system most and how to position your best nutritional delivery system? Utilize PURE Insight™’s advanced soil and water lab testing to dial in YOUR turf’s conditions and how to manage them best.
The rates of photosynthesis and respiration both generally increase with temperature. When photosynthesis exceeds respiration, plants grow and perform to our liking. When respiration exceeds photosynthesis (lack of oxygen primarily), growth slows, stored plant food is consumed, and plants become more susceptible to biotic and abiotic stress.
Optimal ‘ambient’ growth temperatures: cool-season turfgrass 55–83 °F, warm-season turfgrass 68–95 °F. This is why TOMi™ measures in the canopy, at the canopy/soil interface — where the plant actually experiences temperature, not where an air sensor happens to sit. Note that YOUR conditions, particularly moisture management practices, GREATLY influence temperature. While the above are general ambient temperature ranges, maintaining even slightly more than optimum moisture will result in temperatures climbing beyond the optimal range, even when ambient conditions are acceptable. No turf (C3 or C4) enjoys excessive heat in the canopy, and elevated moisture and/or salts (competing for the same moisture plants do) will quickly turn your turf sour.
Temperature slide content courtesy of Dr. Cale Bigelow.
Measurement methods
There is a place for most of these. The mistake is treating an indirect measurement as if it were a direct one.
Any measurement taken above the surface views symptoms only — it does not measure causes. To correct a problem and avoid it next time, you have to measure the cause. As an example, compare NDVI aerial analysis of moisture against measurement taken from the turf’s own perspective and there is no relationship between the two.
A quick, effective blanket measure of moisture across large areas such as fairways, often alongside mowing. But specifications are made in a turf-less medium, dry and full of macropores. Plant material and its density greatly affect penetration, and surface moisture, or its absence, can give a false reading of water the turf can actually use, since it is in the path of the indirect microwave measurement.
Capable of auditing moisture across very large areas. The question for turf is always resolution: what a whole-field average can tell you about a single putting surface that has to perform today. While showing merits for future use if able to target small turf areas, practically it is not where it needs to be for our industry.
Most soil sensors were designed for relatively static environments — installed, calibrated and left in place — then later adapted to turf. TOMi™ was engineered differently. Turf is dynamic, spatially variable and impossible to represent with enough buried sensors. Research supports representative sampling within the critical upper 6 cm bulk region, while repeated insertion of technologies designed to remain stationary can introduce challenges in measurement consistency and comparability. TOMi™ with Ceres™ combines modern sensor engineering with a platform purpose-built around the realities of turfgrass.
Built-for-turf innovation isn’t an adaptation. It’s part of the PURE Insight™ DNA.
Where TOMi™ sits
Emphasis on real-to-imaginary dielectric measurement, elevated frequencies and advanced moisture curve definition — a DIRECT measurement of the relationship between real dielectric permittivity and impedance, tunable to target the turfgrass environment perfectly. This is the family of physics the Ceres™ sensor builds on, tuned specifically for the turfgrass system while remaining autonomously immune to skewness from the multitude of turfgrass dynamics.
Playability
Ongoing PURE Insight™ and PhD collaborative research is looking closely at the relationships between moisture, firmness, ball speed, disease likelihood, stress influences and more.
DID YOU KNOW? Wet conditions do not always mean slow. And dry conditions do not always mean fast, for instance. Turf is unique, having a thatch layer despite sometimes being minuscule. When too dry, this layer causes friction on the ball from multiple straggler leaves pointing in all directions.
Dr. Magro’s research shows that the best ball speed, no matter what the turf, results from just the right amount of water, at the right time, under the right cultural practice regimes IN COMBINATION with other factors (rolling, mowing HOC/direction/repetition, nutritional control, and more). No one thing is the answer, while measuring the system properly sure will lead to one.
Finding your turf’s happy place will result in not only improved conditions, but conditions that are sustained throughout the day, week and season.
Further reading
Dr. Carmen Magro’s comprehensive guide to understanding the vitality of turf and how to monitor it for best decisions sets out a slew of global insights from an extensive list of cooperators and experiences, tying together turfgrass science with the art of turfgrass management. Look for it in 2027!
© C. Magro 2025