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Jens N. Wünsche, Alan N. Lakso, and Terence L. Robinson

Four methods of estimating daily light interception (fisheye photography with image analysis, multiple-light sensors, ceptometer, and point grid) were compared using various apple (Malus domestica Borkh.) tree forms: slender spindle, Y- and T-trellises, and vertical palmette. Interactions of tree form, time of day, and atmospheric conditions with light interception estimates were examined. All methods were highly correlated to each other (r 2 > 0.92) for estimated daily mean percent total light interception by the various tree forms, except that the point grid method values were slightly lower. Interactions were found among tree form, time of day, and diffuse/direct radiation balance on estimated light interception, suggesting that several readings over the day are needed under clear skies, especially in upright canopies. The similar results obtained by using the point grid method (counting shaded/exposed points on a grid under the canopy) on clear days may allow rapid, simple, and inexpensive estimates of orchard light interception.

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Janice Smith, Charles Raczkowski, and Marihelen Kamp-Glass

Crop canopy cover data is used to study canopy structure and crop growth analysis. This study was conducted to determine the easiest and most reliable method of calculating crop canopy cover. Using Decagon Sunfleck Ceptometer was compared with the traditional method (tape measure) of retrieving crop canopy cover data. Data was collected on silage corn (Zea mays) and soybeans (Glycine max L.). The method of collecting data using the ceptometer was simple and quick compared to the traditional method. The ceptometer, even with human variability, was found to be ≈99% accurate. The traditional method was found to have >10% variability. The ceptometer is a much quicker and more reliable tool to use. It appears to decrease the variability in the collection of crop canopy cover data.

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Yaffa L. Grossman and Theodore M. DeJong

Plant dry matter production is proportional to light interception, but fruit production does not always increase with increased light interception. Seasonal daily patterns of light interception by cling peach trees planted in four different planting density/training systems were obtained using a Decagon ceptometer. The High Density V system (1196 trees/ha) intercepted significantly more light than the KAC V and Cordon systems (918 trees/ha). The Vase system (299 trees/ha) intercepted significantly less light than the other systems. Response surfaces using a quadratic model with interactions for time of day and day of year explained 84% to 91% of the variance in the data sets for each training system. Crop yields per acre were greatest for the High Density V, followed by KAC V, Cordon, and Vase, corresponding to the light interception data. A carbon budget model, which incorporated canopy photosynthesis, respiration, and carbon partitioning based on organ growth potentials, was used to simulate seasonal patterns of carbon assimilation, crop dry weights, and individual fruit dry weights.

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Bruce D. Lampinen, Vasu Udompetaikul, Gregory T. Browne, Samuel G. Metcalf, William L. Stewart, Loreto Contador, Claudia Negrón, and Shrini K. Upadhyaya

bar (Ceptometer; Decagon Devices, Pullman, WA) was used by Grossman and DeJong (1998) and McFadyen et al. (2004) to take multiple readings in a regular pattern under the trees. Although all of these methods can provide useful data, they are all

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Juan Carlos Díaz-Pérez

after transplanting (12 May 2009 and 21 May 2010). The level of shading was verified by using quantum sensors of a ceptometer (SunFleck Ceptometer; Decagon Devices, Pullman, WA). Plants were irrigated with an amount of water equivalent to 100% crop

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Ignasi Iglesias and Simó Alegre

distribution was assessed by measuring PAR reflected by the film or by the soil surface using a ceptometer (Sun Scan Accu SS1-UM-1.05; Delta-T Devices, Cambridge, UK) with 64 sensor photodiodes arranged in a line along a 100-cm-long sword. The sword

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David O. Okeyo, Jack D. Fry, Dale J. Bremer, Ambika Chandra, A. Dennis Genovesi, and Milton C. Engelke

ceptometer (AccuPAR model LP-80; Decagon, Pullman, WA) at 0730 hr , 1030 hr , 1330 hr , 1630 hr , and 1930 hr . The ceptometer was held at the grass canopy level (with no grass shading the sensors) in the center of each plot, and readings were taken and

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Bryan Hed and Michela Centinari

. Photosynthetically active radiation ( PAR ) was measured with a ceptometer (AccuPAR LP-80; Meter Group, Pullman, WA) within 2 h of solar noon on the same day under clear, sunny conditions. The in-canopy photon flux values were calculated as the ratio of the within

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Juan Carlos Díaz-Pérez

a ceptometer (Sunfleck PAR ceptometer; Delta-T devices) in the fall season. Incoming and reflected PAR was measured at 14 and 21 d after transplanting (DAT) on clear days at 1300 to 1400 hr . Reflected PAR was measured by placing the ceptometer

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Todd C. Einhorn, Janet Turner, and Debra Laraway

by a circled x. Light measurement. Photosynthetic active radiation ( PAR ) was measured with a ceptometer (AccuPAR LP-80; Decagon Devices, Inc., Pullman, WA) in each of the four experimental trees per replicate plot. PAR measurements were taken at