Inversions are invisible, unless you have the tools to look

A tool designed to identify temperature inversions will help producers better understand when it’s safe to spray their crops.

Innoquest Inc.’s SpotOn Inversion Tester is essentially a pole with a temperature sensor on one end and a readout on the other.

It allows producers to measure the temperature at two levels: one and three metres high.

The tool is one-metre-long so an operator holds it upside down to get a reading at the one-metre height, and turns it right-side-up to get a reading at the three-metre height.

“When it’s satisfied that it has both those temperature measurements, because it does have a sensor in there that tells you if you’re holding it right-side-up or then calculates whether there is an inversion present by comparing the two temperatures,” said Bill Hughes of Innoquest Inc.

If it’s warmer at the three-metre height than at one metre, it will display that a temperature inversion is present.

To achieve accurate air temperature readings, the temperature sensor is shielded, so readings are not affected by solar radiation.

Applications expert Andrew Thostenson from North Dakota State University has tested prototypes of the SpotOn Inversion Tester and he said he’s pleased with it.

Before the availability of a hand-held inversion tester, applicators had to look for indirect signs to detect inversions.

“We are looking at things like dust in the air, whether it hangs, smoke in the air, noise, frost or dew. These are all indirect results of an inversion.

“But really measuring an inversion in a field with some sort of hand-held device has not been available,” he said.

He said researchers from North Dakota State University have settled on the notion that if there is a 0.5 F inversion, spray applicators should be concerned.

“Certainly, when you get a full degree of inverted weather conditions… if I were the applicator, I would shut things down, especially in the afternoon because the weather is probably not going to be favourable going forward into the evening,” Thostenson said.

North Dakota State University is developing a network of remote weather stations that take air measurements at different heights and are capable of detecting inversion.

“Now we only have seven but by time spray season is upon us we will probably have 25 locations. The problem with station is that it doesn’t really tell you exactly what is happening in your field,” Thostenson said.

Topography plays a large role in the intensity and duration of air temperature inversions, so applicators need to assess conditions on a field-by-field basis.

Hughes said the one- and three-metre testing heights come from work conducted by North Dakota State University.

One metre is a height many applications are done at, roughly boom height for row crops, while herbicide is usually applied by aerial applications at three metres.

The development of the SpotOn Inversion Tester came on the heels of considerable damage to U.S. soybeans last year from dicamba drift.

“The product is meant for measuring in-field temperature inversions when a farmer goes to make an application of a dicamba herbicide. In the U.S., the labels have changed and require field-level weather measurements,” Hughes said.

Applicators can use their smartphone to take a photo of the Spot-On Inversion Tester’s display when a reading has been taken.

“When you take it with your cellphone the metadata on the photo attaches GPS co-ordinates, as well as a time and date stamp to that photo, so you have proof that you took the reading, when and where,” Hughes said.

The SpotOn Inversion Tester also takes air temperature readings at boom height, another requirement for dicamba applications.

Thostenson said state regulator agencies in the U.S. act much more favourably toward pesticide operators who have field-level readings of wind speed, temperature, humidity, and now the inversion readings.

“Somebody who is out there taking measurements in the field has a pretty good idea of what’s going on and it’s really hard to be challenged in a courtroom situation when you’ve done your homework and you’ve done your due diligence,” Thostenson said.

The SpotOn Inversion Tester folds in half, to about half a metre in length, making it easier to carry around or stow.

“Some people have recommended when they are filling up from their nurse tank, while you are waiting on the fill, you can take a reading with it because it takes just a minute or so to take a reading,” Hughes said.

The SpotOn Inversion Tester sells retail for US$375.

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