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measurements. Canopy reflectance measurements were made using a six-band multispectral camera (Tetracam Micro-MCA, Chatsworth, CA) flown on a multirotor UAV. The camera was configured with spectral bands at 550, 660, 710, 720, 730, and 810 nm, all 10-nm wide

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of the vegetation reflectance contrast between different wavebands ( Jackson and Huete, 1991 ). The most widely used indices in multispectral remote sensing are the normalized difference vegetation index [NDVI = NIR-R/NIR+R, where NIR is near

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acquired multispectral digital camera image data or from close-proximity sensors. Remote imaging systems generally measure reflected ambient light, whereas some close-proximity sensors collect reflected light that originates from the sensor itself ( Jones

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potato CNS. At the canopy scale, most of the usable methods for crop monitoring are noninvasive, relying on measurements of light transmitted below the canopy or reflected above it. They belong to the remote sensing methodology (based on spectral canopy

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Airborne multispectral image data were compared with intercepted photosynthetic photon flux (PPF) in commercial winegrape (Vitis vinifera) vineyards of Napa Valley, Calif. An empirically based calibration was applied to transform raw image pixel values to surface reflectance. Reflectance data from the red and near-infrared spectral regions were combined into a normalized difference vegetation index. Strong linear response was observed between the vegetation index and PPF interception ranging from 0.15 to 0.50. Study results suggest the possibility of using optical remote sensing to monitor and map vineyard shaded area, thus providing spatially explicit input to water budget models that invoke evapotranspiration crop coefficient based calculations.

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Research at Padova Univ., Italy, during Summer 2003, was carried out to determine the effect on nitrogen fertilization on yield and canopy reflectance of sweet bell pepper (Capsicum annuum). Pepper var. Tolomeo LRP 4993 (Syngenta) was transplanted into plots (24 m2) on 20 May, maintaining 40 cm between plants and 75 cm between rows (3.3 plant per m2). The experimental design was a randomized block with four replicates. Treatments were 6 nitrogen fertilization rates ranging from 0 to 300 kg·ha-1. Nitrogen was distributed at planting and as top dressing, 44 days after planting. All other production techniques were typical of pepper production in the Veneto region. Beginning the second week after transplanting, canopy reflectance was measured weekly using a multispectral radiometer MSR 87 (Cropscan Rochester, Minn.). Fruits were harvested at breaking color stage starting from 21 July to 9 Oct. (8 harvests). At harvest, total and marketable yield, fruit averaged weight and nitrogen content were determined. Maximum yield was recorded at the 120 kg·ha-1 nitrogen treatment, while higher rates proved ineffective at increasing production. Nitrogen rates positively affected fruit weight. The nitrate content of fruits also increased with the nitrogen rates although it remained below the level dangerous for human health. Canopy reflectance was able to detect the different nitrogen treatments only during the late stages of the growth cycle making difficult its use as a tool to drive nitrogen fertilization.

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A 3-year study was conducted in Auburn, Ala., on an established hybrid bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy `Tifway'] stand maintained at a 2.54-cm mowing height. Treatments were level of soil traffic applied via a weighted golf cart to produce turf and soil that received varying amounts of traffic. Dormant bermudagrass was overseeded with perennial ryegrass (Lolium perenne L.) each October, which remained until May of each year. Spectral data were collected monthly using a multispectral radiometer. Percent reflectance data were acquired over 512 discrete wavelengths in visible (VIS) and near-infrared (NIR) ranges. Quarterly data collection included soil penetrometer and bulk density measurements to a depth of 15 cm. After 2 years of traffic, both soil penetrometer and bulk density data indicated statistically significant increases in soil compaction. In general, as traffic increased there were also increases in percent reflectance in the VIS range. Data were subject to temporal variation, however, as values changed with the date of sample collection. The NIR reflectance data provided little consistent correlation to measurements of soil compaction. Use of NIR and VIS radiometry to evaluate turf stress showed some potential, but temporal variation must be considered.

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An experiment was carried out at the Iowa State Univ., Neely-Kinyon Research Station (Greenfield, Iowa) to asses the possibility of growing organic radicchio rosso (Chicorium intybus var. silvestre) in Iowa and to determine the effectiveness of different organic fertilizers. The experiment was a factorial combination of three radicchio cultivars (very early, medium early, and early), three organic fertilizers treatments (non-fertilized control, liquid, and compost based), and two planting dates (11 July and 7 Aug). Treatments were arranged in a split plot design with four replicates. In each sub-plot, plants were transplanted, maintaining 30 cm between plants and 75 cm between rows (4.4 plant per m2). During the growth cycle the crop was managed according to typical production techniques adopted for lettuce. Beginning the first week after transplanting, canopy reflectance measurements were taken every 2 weeks until harvest, using a multispectral radiometer MSR 87 (Cropscan, Inc. Rochester Minn.). At harvest, total and marketable yields were measured and dry matter production was calculated. Yield loss was determined after 15 days of cold storage (4 °C). Cropscan measurement showed no differences among fertilizers treatments, mainly because of the high fertility of the soil (6% organic matter), but different growing patterns among radicchio types. The mediumearly type grew quicker than the other types, and showed the lowest percentage of bolted plants (<4%) and the least preharvest weight loss (5%). Moreover, radicchio demonstrated resistance from the hot and dry Iowa summer even without irrigation, representing a useful alternative crop for both organic and conventional farmers.

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), and Sphaerotheca fuliginea (cucurbits; discussed in this study) ( Farr et al., 1989 ; Texas Agricultural Experiment Station, 1988 ). The purpose of this study was to acquire spectral reflectance data and CIR imagery from plants produced under

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investigated. Bulanon et al. (2013) analyzed hyperspectral images of CBS symptoms in the range of 480–950 nm (spectral resolution of 2.8 nm) with the objective of determining the potential bands to develop a multispectral imaging sensor. They defined four

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