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Discussion in 'Irrigation' started by Gabby, Jul 4, 2010.
Generally a good summary post, but I would like to point a couple of things out.
First, don't use Hunters ET numbers unless you have no other options, they are too general. You would be best served to find accurate ET numbers, either real time or historical for you specific region/area.
Second, clay soils (specifically clay and silty clay) generally have the highest total water holding capacity, not loams. Some loams are close (silty clay loam, clay loam, silt loam). Be careful when you discuss a soils water holding capacity and a soils plant available water, they are not the same. In an ideal world, it would be best to determine you sites specific soil characteristics through testing and not depend on general textural characteristics.
Third, plants ability to extract water from soil varies widely as well as it's ability to handle stress. The need to accurately determine your MAD and properly hydrozoning your site is critical. Using a single value for MAD across different soils types for all plants in the landscape is incorrect. An example of what not to do when determining your MAD is shown in the virtual landscape parameters in the TAMU smart controller study recently discussed.
Uhhh once again Mr I don't get it. The purpose of the study wasn't to figure out the proper programming of a smart controller. The purpose of the study was to determine if one could use the information and tools the manufacturer's provide for you to fulfill the accurate watering needs of a virtual landscape in a specific location. The Hunter ET was one of the controllers measured.
If one wants to learn the skills necessary to tweak a smart controller then they have a course for that. Seeing as how no 2 smart controllers are alike then sticking with one and learning all its intricacies for your area would be wise.
Other than that your post is 100% accurate.
in the real world of residential and light commercial irrigation as long as they are science based. Anything more detailed, and equipment more complex, and irrigation management will not occur or be done correctly.
I was talking about the useful water in a foot of soil and Hunters information is correct. See the following info on soil water relationships and see that we are both correct depending on what we refer to in holding capacity. What really matters is what the plant has use of and loam/silt loam has the edge over anything clay.
If the parameters used to run the study are inaccurate, then how does that affect the outcome of the study?
The purpose of the study was to determine how accurately smart controllers could meet the water demands of a virtual landscape when compared against a real weather station as it applies to the irrigation professional. Controller programming and accurate determination of site parameters are critical for the performance of these controllers. Your continued insistence they are not just demonstrates your complete lack of understanding with regard to these types of controllers.
Then please refer to it as plant available water or available water holding capacity to avoid any confusion.
This is a better reference, given it is probably where they got their numbers.
This is correct, but understand determination of that amount is not as cut and dry as you might believe.
I installed a Rain Bird as a retrofit on one of my old jobs that had an RC. The client was a Dr, but a regular bright guy, not a smart dumb guy if you know what I mean.
This was our first RB and after suing the Hunter a few time in 2009. i bought the unit at the suggestion of the RB rep at a local summer trade show. I sent the tech out and he was flustered with all the programming. Having used only the Hunter which is easy and reading about the RB it seemed like a great idea.
Late spring 2010 the client calls and says he doesn't understand programming this controller. He'd need to be an engineer. I go online and read the installing info. It gave me a headache. No wonder the Doc and my tech were frustrated. I have a degree in hort, worked research in college and now have 40 yrs in biz. The RB Smart controller is like a genius with no common sense. Smart controllers aren't smart at all. But you do need to be smart as well as extremely technically knowledgeable to own and operate one.
Your avg residential site in this country is not going to have many variables other that sun/shade or flat/slopes. The soil will be pretty much the same on the entire site. Only a small portion of the sites will be hydro zoned because of enough plant beds, slope problems or shade to warrant differentiation.
We try to water as much of the perimeter or foundation beds with turf heads adjusted for some back swing, any full circles then going into the beds or locating the perimeter head in to the bed and using a 12" or a riser to clear plant material. As long as the lawn is happy, the ornamentals are happy.
For shade areas covered by rotors you can reduce nozzle size. But what we find is when lawn meets a wooded area, the adjacent unirrigated trees sap both nutrients and water from the perimeter lawn, so we seldom down size nozzles unless the trees are with in the lawn and extensive.
Leave the smart controllers to big sites with big expanses of variables and an on site manager capable of understanding all of the science behind the scene.
If the parameters are inaccurate then its on the manufacturer not the persons doing the study. One has to assume the study authors are performing the settings accurately which I do. Some controllers were set by the manufacturers.
step by step
1. 10 controllers selected
2. virtual landscape created
3. controllers programmed according to the manufacturer's recommendations for that virtual landscape in a specific location in this case the location was the TAMU test plot.
results taken and compared to what the actual watering needs of this landscape are.
A real weather station was on site.
What TAMU is doing, I can assure you having taken their courses and gotten Dr. Fipps philosophy on irrigation, is to show that Cities mandating a smart controller with the built in parameters the manufacturers have provided for their controllers is not in itself always conserving Texas water. This study among all things shows the importance of a water manager whether its a traditional controller or a smart controller.
For the last time this isn't about tweaking a smart controller. Its about judging whether the manufacturer's parameters can be relied on for accurate watering needs. Some did better than others. Some performed well in certain times of the year and poorly in others. Some over watered and some under watered. They all need tweaking for one reason or another.
The parameters of the virtual landscape are the manufacturers responsibility? OK Pete .... whatever you say.
Manufacturers were given the opportunity to review the controllers programming. There is no definitive statement in the report that indicates the controllers where the manufacturers actually supplied programming suggestions/instructions were used.
Don't know why you are pointing this out, but a real weather station was not "on site". The weather station used was the one at the TAMU golf course, which the TexasET network tracks. Unless they setup their test facility right next to that weather station, which there is no indication they did, then it was not "on site".
Is there a good reason why you can't get the details correct Pete?
If you believe this, then you clearly do not understand the study.
No comment ..........