Dear all! The soil variability in Poland is very common. Thus, we can distinguish areas with optimum, insufficient and excessive humidity even on one field. For this reason I am looking for Visual Indices, which would be helpful to detect such areas. Till now, we were working mainly with NDVI and similar VIs. However, the NDVI is more related to biomass, and thus it is useful to distinguish high and low yield areas, but it does not provide information, if the low yields (biomass) result from the shortage, or excess of water? Any ideas? May be MSI (Moisture Stress Index) would be useful?
Dear Ittai, we used and use different sources of data: Green Seeker, Crop Circle. We check or want to check also satellite data, especially those, which can be used without charges (Sentinel 2, Landsat 8). Best regards, Michał
Can you use thermal data?
Does LAI leaf area index will be more related to yield than biomass? in case yes you might want to check the REIP index and the relation it obtained with LAI in this paper.
https://www.researchgate.net/publication/256850034_LAI_assessment_of_wheat_and_potato_crops_by_VENuS_and_Sentinel-2_bands
Article LAI assessment of wheat and potato crops by VENμS and Sentinel-2 bands
Dear Ittai, thank you for the paper and suggestion. In our work, we have no possibility to measure LAI directly, and prefer use satellite, freely available data (mainly Sentinel 2 and Landsat 8). So, we must check REIP. On the other hand, I noted, that the crop (maize, but not only) turns yellow on areas with probable excess of water (although, we must remember about other possible causes of this change, as some nutrient deficiencies), so, if we have no yellow band to check, may be the use of green band form Sentinel 2? I think there is some work to do.
The REIP is not the ultimate solution. It was suggested for your consideration as possible part of a solution for your question.
Since, as you mentioned, there are many parameters that can influence the spectral data, my guess is that it will not be easy to isolate your aim that to the best of my understanding is looking for plant water condition based on soil variability. In that case you might want to get straight to it, try spectrally (map based) detecting the different soils prior to seeding and then look for low LAI or biomass or vigor by spectral indices combined with thermal data.
Perhaps therma data would be the best - within one field with one crop, excessively wet areas would be cooler. For now, I don't know about the potential sources of such free data (Landsat 8 has resolution of about 100m, although resampled to 30).
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