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Russell Galanti, Alyssa Cho, Amjad Ahmad, and Javier Mollinedo

great benefit to macadamia growers. Chlorophyll and other components related to chlorophyll account for ≈75% of leaf N ( Loomis, 1997 ), making chlorophyll a fairly accurate indicator for N status in leaves. The SPAD-502 Chlorophyll Meter (Konica Minolta

Open access

Youngsuk Lee, Hun Joong Kweon, Moo-Yong Park, and Dongyong Lee

leaf chlorophyll meter that has been widely used to estimate foliar Chl and N content in a simple, nondestructive way ( Ata-Ul-Karim et al., 2016 ; Markwell et al., 1995 ). Hereafter, the term SPAD (soil and plant analyzer development) is used to refer

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Yun-wen Wang, Bruce L. Dunn, Daryl B. Arnall, and Pei-sheng Mao

useful index to assess the growth status and leaf N level of a plant ( Seemann et al., 1987 ). For several horticultural crops, leaf N and chlorophyll concentration were found to be strongly correlated when checked using a SPAD chlorophyll meter ( Neilsen

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James A. Hardin, Michael W. Smith, Paul R. Weckler, and Becky S. Cheary

in a measurement protocol using data from a SPAD meter or a multispectral camera image to measure foliar N. The efficacy of multispectral cameras and/or portable chlorophyll meters to quantify N in pecan leaves has not been reported. The objectives of

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M. Wilcox, C.A. Sanchez, and T.M. Blackmer

Several studies in the midwestem United States have shown that chlorophyll meter readings (Minolta SPAD 502) are useful in determining the N status of corn (Zea Mays L.), and show promise as a tool for the efficient N management of corn. Studies were conducted to evaluate the potential of the `chlorophyll meter for evaluating N deficiencies in lettuce (Lactuca sativa L.). Data for chlorophyll meter readings, midrib nitrate-N, lettuce growth rate, and marketable lettuce yield were collected in five N fertility experiments in 1993 and 1994. Chlorophyll meter readings not only varied among lettuce types (butter, cos, leaf, crisphead), but also among cultivars of the crisphead type. Chlorophyll meter readings were generally poorly correlated to midrib nitrate-N levels and marketable lettuce yield. Lettuce leaves have more color variation than corn leaves, and perhaps this variation in relation to the small sensor size on the SPAD 502 confounded readings. The observation that subtle N deficiencies in lettuce are usually manifested in growth rate reduction rather than abrupt color changes may also limit the usefulness of the chlorophyll meter for lettuce.

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Oscar A. Monje and Bruce Bugbee

Two types of nondestructive chlorophyll meters were compared with a standard, destructive chlorophyll measurement technique. The nondestructive chlorophyll meters were 1) a custom built, single-wavelength meter, and 2) the recently introduced, dual-wavelength, chlorophyll meter from Minolta (model SPAD-502). Data from both meters were closely correlated with destructive measurements of chlorophyll (r2 = 0.90 and 0.93; respectively) for leaves with chlorophyll concentrations ranging from 100 to 600 mg·m-2, but both meters consistently overestimated chlorophyll outside this range. Although the dual-wavelength meter was slightly more accurate than the single-wavelength meter (higher r2), the light-scattering properties of leaf cells and the nonhomogeneous distribution of chlorophyll in leaves appear to limit the ability of all meters to estimate in vivo chlorophyll concentration.

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Y.C. Li, A.K. Alva, D.V. Calvert, and M. Zhang

Rapid and accurate diagnosis of plant nutrient deficiency is critical for growers to use fertilizer economically and to minimize environmental concern. The objective of this study was to evaluate the use of leaf chlorophyll meter (SPAD-502) to predict nitrogen status and yield response of grapefruit trees. The study includes two irrigation treatments, three fertilizer sources, and four fertilizer rates. No significant differences in SPAD readings and leaf N were found between two irrigation treatments. Correlations between SPAD readings and leaf N were higher for the spring flush (r = 0.61) than that for summer flush (r = 0.49). There were poor relations between SPAD meter readings and the extractable chlorophyll content in the spring flush on a dry-weight basis (r = 0.25). Higher correlations between SPAD meter readings and N rates or fruit yields than between leaf N concentrations and N rates or fruit yield.

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Seong-Tae Choi, Doo-Sang Park, Seong-Mo Kang, and Soo-Jeong Park

subjective; different people perceive it differently. A quicker and quantitative method is thus needed. The SPAD-502 chlorophyll meter has been successfully used in assessing leaf N status of apple ( Neilsen et al., 1995a , 1995b ; Park et al., 2007

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Ian R. Rodriguez and Grady L. Miller

Because high rates of nitrogen fertility are necessary for producing high-quality turfgrasses, quick, reliable methods of determining the N status of turfgrasses would be valuable management tools. The objective of this study was to evaluate the capacity of a hand-held chlorophyll meter (SPAD-502) to provide a relative index of chlorophyll concentrations, N concentrations, and visual quality in St. Augustinegrass [Stenotaphrum secondatum (Walt.) Kuntze]. Two experiments were conducted in a greenhouse in 1998 to evaluate the utility of SPAD readings. Established pots of `Floratam' were subjected to weekly foliar Fe treatments at Fe rates of 0 and 0.17 kg·ha–1 for 4 weeks. Six weekly nitrogen fertilizer treatments were applied in the form of ammonium sulfate at N rates of 0, 5.75, 11.5, 17.25, and 23 kg·ha–1 for 4 weeks. Greenhouse SPAD readings were not affected by Fe treatment, but N treatments resulted in differences in SPAD readings, visual quality, and chlorophyll concentrations. The readings were positively correlated with chlorophyll concentrations (r 2 = 0.79), visual ratings (r 2 = 0.74), and total Kjeldahl nitrogen (TKN) (r 2 = 0.71). Readings taken from field-grown `Floratam', `Floratine', and `Floralawn' St. Augustinegrass were poorly correlated (r 2 < 0.63) with chlorophyll concentrations and TKN. Unless future techniques improve dependability of the SPAD meter under field conditions for measuring chlorophyll and N concentration of a stand of turfgrass, the usefulness of such readings for the management of St. Augustinegrass seems limited.

Open access

Ji-Jhong Chen, Shuyang Zhen, and Youping Sun

Leaf chlorophyll content is an important index for plant N status, photosynthesis capacity, and stress tolerance ( Taiz et al., 2015 ). It is common to estimate leaf chlorophyll content using nondestructive optical chlorophyll meters ( Ferrarezi