This work proposes a methodology, by light-scanning below the canopy, to directly estimate the photon flux radiation (400–1200 nm) intercepted by single or row canopies. The system is based on the assumption that the light intercepted by the canopy, at a particular time, corresponds to the difference between the incoming potential radiation on a ground surface area (able to include the ground area shaded by the canopy), and the actual radiation influx to that area in presence of the canopy. To this purpose, light-scanning equipment has been designed, built, and tested, whose main components are two aligned multi-sensor bars (1.2 m long) and a CR10 data logger, equipped with an AM 416 Relay Multiplexer (Campbell Sci. Ltd., U.K.). The radiation sensors (BPW 14N TELEFUNKEN) were chosen because of their spectral sensitivity, along with low cost. The sensors have been placed along the bars, at 5-cm intervals, and fitted with a Teflon® diffuser to provide a cosine correction. Radiation measurements are taken moving parallelly the bars on the ground, step by step, to monitor a sample point grid (5 cm by step length). Preliminary radiation scans were taken during the summer in a 3-year-old peach orchard, trained as delayed vasette. Measurements were taken for a single canopy at various hours of the day. Moreover, radiation scans were taken at the same hour, over a 3-day timespan, while gradually defoliating the canopy. A custom-built software program has been developed for data handling. Mathcad software (Mathsoft Inc., U.S.) has been used to display the canopy shade image projected on the ground, the quantum map of the monitored area, and to calculate the light influx on the whole canopy. Moreover, the light spots on the ground determined by foliage gaps have been identified and the amount of radiation reaching the ground has been be estimated.
different experimental groups or treatments if a plot of the denominator versus the numerator of the ratio-based expression has a nonzero y -intercept and the values for either the denominators or numerators differ among experimental groups or treatments
. Mathematical principles apply to all ratio-based evaluations of efficiency. If a plot of the denominator vs. the numerator produces a nonzero y intercept, ratios are related to their components (denominator and numerator) ( Atchley et al., 1976 ; Packard and
ratio-based expressions are dependent on the value of the denominator if a plot of the denominator versus the numerator of ratio components produces a linear function with a nonzero intercept ( Atchley et al., 1976 ; Packard and Boardman, 1988
-POTATO and LINTUL-POTATO (University of Hawaii, Honolulu, Hawaii). The SUBSTOR-Potato crop soil weather model takes into consideration daily air temperature, photoperiod, intercepted solar radiation, soil water, and nitrogen supply. The model simulated fresh
obtained colorimeter L*, a*, and b* data from each patch, and applied linear regression to determine slopes, y-intercepts, and regression coefficients. The TACT dialog box ( Fig. 1 ) allows users to enter correction values for slope and y-intercept as a way
growth stages and underwatering for later growth stages. For this reason, correction factors or crop coefficients (K c ) are used to adjust ET for a particular crop and its growth stage. Time-averaged K c values have been reported for a wide range of
, carborundum was rinsed off the leaves to improve light interception, and the plants were maintained in aphid-proof cages. All ‘Gray Zucchini’ plants were seeded in Metro-Mix 200 (Scotts-Sierra Horticultural Products Company, Marysville, OH) in 160 mm diameter
circular motion eight to 10 times as if painting the leaf with inoculum. After inoculation, carborundum was rinsed off the leaves to improve light interception, and the plants were maintained in aphid-proof cages. All ‘Gray Zucchini’ plants were seeded in
apple cortex samples [y = 1.4166Ln(x) – 3.3306, r 2 = 0.9696, P < 0.001]. Each data point represents the mean ± se of 16 measurements. Both P-V curves of apple cortex tissue obtained before and after correction ( Fig. 3 ) followed the typical