Abstract
Documenting crop senescence rates is often difficult because of the need for frequent sampling during periods of rapid change and the subjective nature of human visual observations. The purpose of this study was to determine the feasibility of using images produced by a digital camera to measure the senescence rate of wheat and to compare the results with changes in greenness determined by two established methods. Measurements were made as part of an experiment to determine the effects of elevated C0 2 and limited soil nitrogen on spring wheat ( Triticum aestivum L.) at the University of Arizona's Maricopa Agricultural Center, near Phoenix, AZ. “Greenness” measurements were made during senescence of the crop with a color digital camera, a hand‐held radiometer, and a SPAD chlorophyll meter. The green to red (GIR) for each pixel in an image was calculated and the average GIR computed for cropped images from a digital camera representing 1 m 2 for each treatment and sample date. The normalized difference vegetation index (NDVI) was calculated from the red and near‐infrared canopy reflectances measured with a hand held radiometer. A SPAD reading was obtained from randomly selected flag leaves. All three methods of measuring plant greenness showed similar temporal trends. The relationships between GIR with NDVI and SPAD were linear over most of the range of G/R. However, NDVI was more sensitive at low values than G/R. GIR was more sensitive above GIR values of 1.2 than SPAD because the upper limits of SPAD measurements were constrained by the amount of chlorophyll in the leaf, while GIR responded to both chlorophyll concentration in the leaves as well as the number of leaves present. Color digital imaging appears useful for quantifying the senescence of crop canopies. The cost of color digital cameras is expected to decrease and the quality and convenience of use to improve.
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Claims 7
Claim · model-written summary
Digital camera, radiometer and SPAD greenness measures showed similar temporal trends.
- Taxon
- Wheat
Triticum aestivumt0 - Outcome
- plant greennesse0
- Comparator
- All three methodse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“All three methods of measuring plant greenness showed similar temporal trends”
t0“Wheat”
Claim · model-written summary
GIR related linearly to NDVI across most of its range.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- relationships between GIR with NDVIe0
- Qualifier
- over most of the range of G/Re0
- Comparator
- NDVIe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The relationships between GIR with NDVI and SPAD were linear over most of the range of G/R”
t0“Wheat”
Claim · model-written summary
GIR related linearly to SPAD across most of its range.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- relationships between GIR with NDVI and SPADe0
- Qualifier
- over most of the range of G/Re0
- Comparator
- SPADe0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The relationships between GIR with NDVI and SPAD were linear over most of the range of G/R”
t0“Wheat”
Claim · model-written summary
NDVI was more sensitive than G/R at low values.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- more sensitivee0
- Direction
- more sensitivee0
- Qualifier
- at low valuese0
- Comparator
- G/Re0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“NDVI was more sensitive at low values than G/R”
t0“Wheat”
Claim · model-written summary
GIR was more sensitive than SPAD above GIR 1.2.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- more sensitivee0
- Direction
- more sensitivee0
- Qualifier
- above GIR values of 1.2e0
- Comparator
- SPADe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“GIR was more sensitive above GIR values of 1.2 than SPAD”
t0“Wheat”
Claim · model-written summary
GIR responded to leaf chlorophyll concentration and leaf number.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- GIR responded to both chlorophyll concentration in the leaves as well as the number of leaves presente0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“GIR responded to both chlorophyll concentration in the leaves as well as the number of leaves present”
t0“Wheat”
Claim · model-written summary
Digital color imaging was judged useful for measuring canopy senescence.
- Taxon
- WheatTriticum aestivumt0
- Outcome
- quantifying the senescence of crop canopiese0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Color digital imaging appears useful for quantifying the senescence of crop canopies”
t0“Wheat”