Developing rapid crop canopy assessment methods using ground and aerial remote sensing techniques

Momtanu Chakraborty

Rapid advancements in remote sensing technologies can overcome the limitations of manual diagnosis of crops and orchards leading to better management practices. In pursuit of such integrated technological solution, the first objective of this study focusses on development and evaluation of ground based canopy characterization system which can aid in rapid and accurate extraction of canopy parameters. Therein, 3D time of flight sensors were evaluated to estimate canopy growth for drip surface and sub-surface irrigation treatments. Canopy structural parameters were extracted from 3D reconstructed point cloud data. Preliminary studies were conducted on 14 sample apple trees for estimating the accuracy of the methods used. The manual canopy volume measurements had a strong correlation to the 3D light detection and ranging data (LiDAR) (r=0.86) and 3D imaging sensor derived volume (r=0.65). 3D LiDAR derived tree height had a strong correlation (r=0.83) with measured height. For studied treatment block of grapevines, the different rate of irrigation did not have a significant effect on canopy growth which reveals that lower rate of irrigation may be used in vineyards for sustainable use of water. This aspect need further revalidation given the high snowpack of 2016-17 winter season. Nonetheless, the methods developed to extract canopy parameters from point cloud data, can also be used for other applications such as canopy map derived precise spraying rates. The second objective of this study was to assess the effects of modified center pivot sprinkler irrigation systems, i.e. low elevation spray application (LESA) and mid elevation spray application (MESA), in corn towards crop vigor and canopy temperature. Multispectral and thermal imagery acquired with small unmanned aerial system were used to extract these canopy parameters throughout the crop growing season. LESA irrigated area had less canopy vigor and higher canopy temperature than MESA throughout the season. On further inquiry, it was discovered that the LESA sprinklers used were pulled off by corn and the hoses destroyed slices of the LESA irrigated area which affected the results. Further studies need to be conducted to verify which sprinkler irrigation system is better for corn in terms of crop vigor and canopy cooling.

Developing rapid crop canopy assessment methods using ground and aerial remote sensing techniques

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