Articles
Comparison of different vegetation indices computed from hyperspectral leaf reflectance data in processing tomato
Article number
1382_7
Pages
51 – 58
Language
English
Abstract
Significant amount of freshwater is used in the production of irrigated crops.
Better irrigation management and scheduling will lead to increased water use efficiency.
Modern equipment such as thermal cameras, porometers and hyperspectral spectroradiometers are in service to plant water stress monitoring.
However, research should provide data and test results on the specific use of these devices such as scheduling the irrigation of a particular crop.
An experiment was set up at the experimental farm of the Institute of Horticultural Sciences at Szárítópuszta, Gödöllő, Hungary in 2022. Leaves of processing tomato hybrid H1015 were measured once a week around solar noon with an ASD Hand-held 2 hyperspectral spectroradiometer.
The measurements were conducted in the 325-1075 nm spectral range in 1 nm steps (UV/VIS/NIR). The contact probe was attached to a leaf clip thus, there was not any disturbance from the environment during the measurement.
There were four different water supply levels set, covering the 100, 75, and 50% of plants water demand (crop evapotranspiration) with drip irrigation system and these treatments were compared to a non-irrigated control.
These treatments provided the different levels of water stress which could be well controlled in 2022 due to the severe drought during the growing season.
The monitoring was continued for 10 weeks until the end of the growing season.
Irrigation was ended in the beginning of the ripening period.
Different vegetation indices were computed from the reflectance data as it can be found in the library of formulas in the Index DataBase (https://www.indexdatabase.de). The nomenclature of indices also follows this database.
In this study, 228 indices were evaluated in total.
We found 7 indices that showed the differences induced by the varying level of water stress between treatments throughout the whole monitoring period according to the mean of the index values.
These indices were the following: Difference 678/500, mNDVI, PSRI, SR800/960, WBI, Simple ration355/365 gk, SIPI1. Since, these indices showed differences in the means of the index values from the first week, these may be useful in the early detection of water stress as well.
However, more data are needed to determine the functional threshold values of these indices to use them in irrigation scheduling.
Better irrigation management and scheduling will lead to increased water use efficiency.
Modern equipment such as thermal cameras, porometers and hyperspectral spectroradiometers are in service to plant water stress monitoring.
However, research should provide data and test results on the specific use of these devices such as scheduling the irrigation of a particular crop.
An experiment was set up at the experimental farm of the Institute of Horticultural Sciences at Szárítópuszta, Gödöllő, Hungary in 2022. Leaves of processing tomato hybrid H1015 were measured once a week around solar noon with an ASD Hand-held 2 hyperspectral spectroradiometer.
The measurements were conducted in the 325-1075 nm spectral range in 1 nm steps (UV/VIS/NIR). The contact probe was attached to a leaf clip thus, there was not any disturbance from the environment during the measurement.
There were four different water supply levels set, covering the 100, 75, and 50% of plants water demand (crop evapotranspiration) with drip irrigation system and these treatments were compared to a non-irrigated control.
These treatments provided the different levels of water stress which could be well controlled in 2022 due to the severe drought during the growing season.
The monitoring was continued for 10 weeks until the end of the growing season.
Irrigation was ended in the beginning of the ripening period.
Different vegetation indices were computed from the reflectance data as it can be found in the library of formulas in the Index DataBase (https://www.indexdatabase.de). The nomenclature of indices also follows this database.
In this study, 228 indices were evaluated in total.
We found 7 indices that showed the differences induced by the varying level of water stress between treatments throughout the whole monitoring period according to the mean of the index values.
These indices were the following: Difference 678/500, mNDVI, PSRI, SR800/960, WBI, Simple ration355/365 gk, SIPI1. Since, these indices showed differences in the means of the index values from the first week, these may be useful in the early detection of water stress as well.
However, more data are needed to determine the functional threshold values of these indices to use them in irrigation scheduling.
Authors
S. Takács, Z. Pék, G. Palotás, E. Czinkoczki, L. Helyes
Keywords
precision irrigation, index, leaf reflectance, vegetation index
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