Hi all, newbie here and learning fast.
Does anyone have a suggestion on the best indices to use to detect nitrogen levels in plants, or even soil? I think this can be done using a multispectral set-up, with the crop reflectance showing high/low levels of nitrogen. But what is the best index to use?
I understand this is a hot topic at the moment, with fertilizer costs on the increase.
Thanks for any advice!
Early in the season you can use NDVI and later on when the canopy is closed NDRE:
There also special indices like the REIP, which showed to be very sensitive to nitrogen levels.
Thanks. Is the REIP indice available in P4DF?
Yes PIX4Dfields has a âcustom index calculatorâ tool allowing you to calculate any index you like. But of course it depends if your sensor has the needed spectral bands for any given index. You can read more about the REIP index here: IDB - Search results for »REIP«
Thanks. Iâm not clear how to construct the formula in P4DF though. That link you kindly provided shows formula as the attached, but the Index Calculator doesnât offer those options. The only available band is âRedâ, no Red Edge (for example).
How should it be transposed? It would be great if P4DF contained plenty of indices already.
The reason is that your sensor does not have the bands required for that index. You can use the satellite Import tool, if you want to experiment with those indices, as the satellite data comes with a lot of bands.
In general Pix4dfields supports the most common indices and only suggest you those which work with the bands your senor offers.
Understood, thank you.
Hereâs another one: how does P4DF deal with âto the power ofâ in a formula? Please see attached for TSAVI:
What would the correct formula look like in P4DF?
Hi,
You should type (1+ 0.33^2).
Best,
Hello! @lowaltitude ! How was your experience detecting nitrogen levels? What index wroked the best for you?
Hi. We use NDVI at the start of the season, NDRE as the canopy is full, and have started exploring NIRv which is meant to be more sensitive than NDVI.
Hi @Julius_Petri, @Jose.Arnaudo,
I am using a DJI Mavic 3M and have calculated the REIP using an approximation formula. When I click on âPreviewâ in the PIX4Dfields calculation window the index is displayed. However, when I apply the calculation, the index does not appear in the main window. Within the info section, the mean value and standard deviation (SD) are calculated and displayed numerically. Could this be a visualization issue, or is there a trick to solve this? I can provide you screenshots and the dataset for analysis upon request.
Thx
Franz
Hi, as you donât have the correct bands for REIP index, the values you obtain might be corrupted for PIX4Dfields to display. What formula are you using?
The formula doesnât make sense. 780-700 should be reflectances referring to those bands nmâŠ
Anyway, I was able to estimate the index using your formula on fields with low biomass, make sure you properly set the histogram min and max, as well as turning Histogram equalization ON.
On fields with saturated NDVI, it breaks.
