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Ceres Imaging Blog

Aerial imaging & agriculture tech news for farmers

Research Study Validates Imagery for Pistachios

Recently published research in the peer-reviewed journal Remote Sensing demonstrates the effectiveness of our thermal imagery in detecting water stress in pistachio orchards, echoing the results of the extensive trials in almonds with UC's Blake Sanden over the past several years. Figure 2. Images from the airborne flight on July 21, 2016 showing the crowns of individual trees in our almond (upper) and pistachio (lower) study plots (yellow trapezoid). Images on the left (a,a’) are RGB photos of the almond and pistachio study orchards, in the middle (b,b’) are false-color near infrared images and images on the right (c,c’) are the thermal images showing the extraction of pure vegetation pixels to estimate canopy temperature.

Specifically, the study details how

  • This university-led research study demonstrates the accuracy of thermal imagery provided by Ceres Imaging in measuring pistachio tree water stress at rates similar to those of almond trees.
  • It provides scientific validation that thermal imagery is “helpful for upscaling irrigation information from plant to field scale and thus may be used by farmers for making day-to-day irrigation management decisions.”
  • It concludes, “in the absence of a useful, practical, and affordable tool for the grower to measure plant water status of an entire orchard, we have shown that thermal-based remote sensing can be successfully used to determine the water stress.” 

Published: 10 December 2018, Remote Sensing 2018, 10(12),
Site: https://www.mdpi.com/2072-4292/10/12/2001/htm

Scientific Summary: This study explored the feasibility and accuracy of multispectral and thermal remote sensing imagery to estimate evapotranspiration of pistachio and almond trees during an entire growing season. The study was conducted in Madera County, CA and was carried out by researchers from UC Davis, UC Co-Op Extension, and others. The study found “statistically significant” outcomes in pistachios and almonds and concluded that “the combination of crop evapotranspiration models with remotely-sensed data is helpful for upscaling irrigation information from plant to field scale and thus may be used by farmers for making day-to-day irrigation management decisions.”

The findings assessed a combination of other technologies including satellite and stem water potential measurements, in addition to thermal imagery provided by Ceres Imaging’s sensor package flown using fixed-wing aircraft. In assessing the commercial relevance of such technologies, the report found significant statistical limitations with satellite-derived NDVI as well as practical limitations with stem water potential (SWP) measurements.

Satellite-derived NDVI: “A data set consisting of 25 dates of Landsat-8 Level 1 product images for atmospherically-corrected, top of the canopy normalized difference vegetation index (NDVI) covering both orchards was acquired from the USGS … Although simple and widely-applied, this method (NDVI) may be too simplistic for crops undergoing deficit-irrigation scheduling because it only accounts for the potential evapotranspiration that a crop would have with no modification in stomatal conductance or crop coefficient (Kc) due to water stress. In addition, these techniques assume that variations in potential crop evapotranspiration (ETc) are linearly related to canopy size, and are not sensitive to crop phenology and canopy architecture [13].”

Stem Water Potential Measurements: “Some researchers argue that plant-based approaches are preferable (to remote sensing) approaches. Among them, midday stem water potential has been commonly used as a precise plant water status indicator. Nevertheless, due to major inconveniences in measuring (stem water potential) manually at large scales, new approaches based on thermal remote sensing imagery have been successfully developed to estimate (stem water potential) in woody crops.”

The study compared Stem Water Potential measured on the ground with the crop water stress index (CWSI) estimate derived from Ceres imagery: 

Figure 11. Comparison between observed (flux towers) and modelled actual daily evapotranspiration (ETaobs, ETamodel) in (a) almonds and (b) pistachios.

We at Ceres Imaging are very excited to be part of this pioneering research and look forward to expanding on our relationship with major universities this coming season.

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