Table 1.
Characteristics of some proximal optical sensors with potential for use for nitrogen (N) management of vegetable crops.
| Sensor Type | Device † | Manufacturer | Measuring Principle | Wavelengths Used (nm) | Scale |
|---|---|---|---|---|---|
| Chlorophyll meter | SPAD-502 | Konica Minolta (Tokyo, Japan) | Transmittance | 650, 940 | Leaf |
| N-tester | Yara International (Oslo, Norway) | Transmittance | 650, 960 | Leaf | |
| atLEAF+ | FT Green LLC (Wilmington, DE, USA) | Transmittance | 660, 940 | Leaf | |
| MC-100 Chlorophyll Concentration Meter | Apogee Instruments Inc. (Logan, UT, USA) | Transmittance | 653, 931 | Leaf | |
| CCM-200 Chlorophyll Content Meter Plus | Opti-Sciences Inc. (Hudson, NH, USA) | Transmittance | 653, 931 | Leaf | |
| DUALEX | Force-A (Orsay, France) | Transmittance | 710, 850 | Leaf | |
| MULTIPLEX | Force-A (Orsay, France) | Fluorescence | 516, 685, 735 | Leaf | |
| Reflectance sensor | MSR5/87/16R | CropScan Inc. (Rochester, MN, USA) | Reflectance (passive ‡) | 460, 510, 560, 610, 660, 710, 760, 810 | Canopy |
| CropSpec | Topcon Positioning Systems, Inc. (Livermore, CA, USA) | Reflectance (passive) | 730-740, 800-810 | Canopy | |
| Spectral Reflectance Sensor | METER Group, Inc. (Pullman, WA, USA) | Reflectance (passive) | 532, 570, 650, 810 | Canopy | |
| OptRx Crop Sensor | Ag Leader Technology (Ames, IA, USA) | Reflectance (active ‡) | 670, 728, 775 | Canopy | |
| N-sensor ALS | Yara International (Oslo, Norway) | Reflectance (active) | 670, 730, 760 | Canopy | |
| Crop Circle ACS 430 | Holland Scientific (Lincoln, NE, USA) | Reflectance (active) | 670, 730, 780 | Canopy | |
| Crop Circle ACS 470 | Holland Scientific (Lincoln, NE, USA) | Reflectance (active) | 450, 550, 650, 670, 730, 760 | Canopy | |
| RapidScan CS-45 | Holland Scientific (Lincoln, NE, USA) | Reflectance (active) | 670, 730, 780 | Canopy | |
| GreenSeeker | Trimble Inc. (Sunnyvale, CA, USA) | Reflectance (active) | 650, 770 | Canopy | |
| GreenSeeker Handheld | Trimble Inc. (Sunnyvale, CA, USA) | Reflectance (active) | 660, 780 | Canopy | |
| Flavonols meter | DUALEX | Force-A (Orsay, France) | Fluorescence | 375, 650 | Leaf |
| MULTIPLEX | Force-A (Orsay, France) | Fluorescence | 590, 735, 985 | Leaf |
† Trade or manufacturers’ names mentioned are for information only and do not constitute endorsement, recommendation, or exclusion. ‡ Active or passive refers to whether the sensor is fitted or not with an own light source, respectively.