Since the mid 90's, irrigation decisions were made using data from our on site weather station. Many times it boiled down to a gut feeling when it came down to watering your golf course based on weather patterns. Today, watering, hand watering is determined by using a soil moisture sensors as the one pictured below.
Soil moisture readings are taken over several locations around the green with an average of each green recorded. Our meter records soil moisture data to 3" depths. The solid tines send out an electrical pulse into the soil and is recorded as real number that determines the volumetric water content of each sample. (%VMC.) Scientifically this is called "Time-domain reflectrometry." Technical jargon I know, but I finally have a real number I can use along with the data the weather station supplies.
I've used the data from the moisture meter to rank all 31 putting greens on the golf course. The spreadsheet lists greens from the driest to the wettest. (#15 is the wettest green on the golf course and thus is watered totally different than the others.) So if it is dry, I can quickly probe the driest of greens to determine if and how much irrigation water we'll schedule for that night. The moisture meter also alerts us to dry soil conditions before they appear. Hand watering is ordered and sprinkler rotation is checked.
I make changes to irrigation run times for each green to attain a balance of plant available moisture across the course. I know this is an unattainable goal of putting green consistency, but we strive non the less for the sake of reduced pumping electrical costs and pesticide, fertilizer inputs. It is not perfect, but beats the hell out of my trusted soil probe screw driver. Now did I squeeze the water out of the soil, its organic matter or the turf grass plant? With my trusted moisture meter, I no longer guess. _Mk