To put it simply, a lot! There is no direct relationship between the two. While TDR is affected by changes in the soil, compaction, soil type, EC levels, etc, the POGO is not. You get a precise and accurate measurement with POGO every time. TDR may report 20% moisture one day and give that same 20% moisture reading even after you fertilize, irrigate with non-neutral water, compact your turf or anything else to change the dynamics of the turf system.
The margin of error for the POGO is less than 1%, so you can remain confident that a 20% moisture reading by a POGO is the same 20% you see at other times. No one can make this claim.
If you have used a TDR device for some time are trying to make a correlation between the number you are comfortable with and the POGO measurement, POGO measures the most dominant region of the turf system that is responsible for moisture exchange and salinity exchange. This holds true with deep and shallow roots or with a clay and sandy loam. The POGO sensor is targeted to measure the bulk activity for that region. This is the difference between a TDR measurement and a POGO measurement.
If you are used to a TDR device and want to find a workable range for your POGO, find the average of all the greens (or other target zones) on your property using the POGO. Take 9 to 12 samples per green, 24 or more on fairways, on a day that you feel your turf is where you want it. Set the zone average as your mid point between the high and low warning settings. Give yourself 3% to 4% on each side of that number. We recommend you set your critical high and critical low values 3% to 4% above/below the high/low numbers.
- Critical High (30%)
- High (26%)
- Zone Average (22%)
- Low (18%)
- Critical Low (14%)
This will get you in the ball park moving forward with POGO. You can then use trends and Visual Insight to know when you are outside of your target range. With this information you can find out if your turf is draining more rapidly or holding water, distributing EC uniformly from fertilizer applications, or many other insights that the POGO offers.
Most users will get into this range and then bring the continue to bring the margins in further to continue improving efficiency after correlating what happens after irrigation, rain, fertilizer applications, etc. You can make notes and pictures in the app to analyze those events; even cultural practices like spiking, vertical mowing, core cultivation, and deep tine. You’ll probably find, as others do, that the number you were used to with other technology wasn’t your ideal number at all.
Over time, you'll come to learn that trends are far more important than a single sample. POGO is about those trends and once you get used to that, it will serve you very well.