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Dr Dario Stefanelli, from Agriculture Victoria, describes how to interpret graphs developed from DA meter data in the following video.

Understanding DA meter data using graphs

Dr Dario Stefanelli, from Agriculture Victoria, describes how to interpret graphs developed from DA meter data.

Video transcript - Understanding the DA meter data using graphs with Dr Dario Stefanelli

Through previous videos, we discussed several methods of using the DA meter, so how to measure in the field, how many measurements to take, how to monitor and, how to download the data. Now, what, in this video we are going to discuss is how to take the data and produce a graph. Graphing is a very important visual tool to understand that the maturity and the development of your fruit in the field.

In the X axis, we have the date. So the timing of when you collected the data in the field, and then the Y axis, we have the value that the DA meter gives you at that particular time in point. The graph clearly explains, in time, the maturity development of the fruit in the field. Each spot is the date of when that collection of data, when the monitoring occurred.

It becomes important because visually you're, you're able to always understand where the fruit, the maturity of the fruit, is at that particular time, and you are able to plan logistically everything that is happening in the farm.

So through a line like this one, each spot gets added every week. So very early on it is possible to start understanding how the maturity is and predict eventually, where it could be, the ideal moment of harvest.

This particular graph, specifically, explains the maturity development of August Flame’ in the 2016 season. It is very important, from a logistical perspective of the farm, to have as many monitoring as possible, because you would have several varieties, that is not only this one. Every variety will have a different graph, a different rate of dropping of maturity. And this becomes extremely important to understand where always you are. And several situations inside of the farm could change the development of the maturity of the fruit. Like, for example, if you have different training systems, different irrigation regimes. If you have a different blocks with different soil, all of those could have an effect on your maturity and therefore monitoring and creating a graph like this one becomes even more important to really define the logistics in the farm.

Here, we have an example of two different training systems for the cultivar ‘August Flame’. It is a peach in 2016. We have a Tatura Trellis on the red line, and we have a vertical axis on the blue line. As you can see the maturity, they developed the more or less similarly up to roughly 26th, 27th of January, and then the vertical leaders slowed down a bit. It had a moment to where the maturity slowed and then, then started again with a similar rate. And this makes an incredible, important again, visual tool for you to understand that two different training systems would have different moments of when to harvest.

Considering the optimal harvest that you want to achieve. And let's say, for example, in this case would be at the level of DA of one. By starting monitoring early on, you would be able, because you end up with two different lines, that you visually and physically are able to distinguish, you would be able to understand and plan accordingly that between the two different systems you end up with roughly four days of difference on when you should harvest.

As we mentioned before, monitoring the various situation that you have in your farm is extremely important because, there could be differences between the different position, the different regimes, the different irrigations, everything in your farm could actually become a difference in where would be the ideal moment of harvesting. And through graphing you gain, you have a very powerful tool and especially you have a database to where to record these changes. These allow you to make a decision much more objectively.

Graphing as a very powerful tool, as we said before, becomes even more important when you start considering that you can graph the same variety in different seasons. Here, we see for example, in the, again, “August Flame’ on Tatura Trellis in both 2016 in red and 2015 in purple. It becomes immediate, even from the starting when even then you start to have the first development of maturity, even from the starting, it is possible to see that the season, in 2015, was much delayed compared to the 2016 one.

In the next videos we will show and explain how to achieve and plot these graphs.

What does the DA meter do?

The DA meter measures the flesh greenness by reflectance of two wavelengths (670 and 720 nm) of light, near the chlorophyll-a absorbance peak. The reflectance is expressed as an index of absorption difference (IAD) scaled from 0 to 3 (green). Comparison of IAD with fruit ethylene production for many cultivars has shown a strong inverse relationship supporting the DA meter as a tool to measure fruit maturity.