Using a Chlorophyll Meter to Determine the Chlorophyll Concentration, Nitrogen Concentration, and Visual Quality of St. Augustinegrass

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 (r2 = 0.79), visual ratings (r2 = 0.74), and total Kjeldahl nitrogen (TKN) (r2 = 0.71). Readings taken from field-grown `Floratam', `Floratine', and `Floralawn' St. Augustinegrass were poorly correlated (r2 < 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.

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Inherent Limitations of Nondestructive Chlorophyll Meters: A Comparison of Two Types of Meters

HortScience ◽

10.21273/hortsci.27.1.69 ◽

1992 ◽

Vol 27 (1) ◽

pp. 69-71 ◽

Cited By ~ 133

Author(s):

Oscar A. Monje ◽

Bruce Bugbee

Keyword(s):

Light Scattering ◽

Measurement Technique ◽

Chlorophyll Concentration ◽

Dual Wavelength ◽

Chlorophyll Meter ◽

Chlorophyll Concentrations

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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Effectiveness of Chlorophyll Meter Measurement in Winter Wheat at Field Scale Level

Agriculture (Pol nohospodárstvo) ◽

10.2478/agri-2014-0005 ◽

2014 ◽

Vol 60 (2) ◽

pp. 41-49 ◽

Cited By ~ 1

Author(s):

Vojtěch Lukas ◽

Fernando Rodriguez-Moreno ◽

Tamara Dryšlová ◽

Lubomír Neudert

Keyword(s):

Winter Wheat ◽

Plant Height ◽

Growth Parameters ◽

Nitrogen Concentration ◽

Chlorophyll Concentration ◽

Nutrition Status ◽

Sampling Point ◽

Area Index ◽

Chlorophyll Meter ◽

Nutritional Deficit

Abstract This paper examines the relationship among chlorophyll meter Yara N-Tester readings, nutrition status and growth parameters (leaf area index (LAI), plant height) of the winter wheat plants. Data used in this study were collected in 2010 from two fields located in the Czech Republic (area 52 and 38 ha) from different farms, both with uniform and conventional crop management. The monitoring of crop stands was done at growth stage BBCH 30 in a regular sampling grid with 150 m distance between points (27 and 18 points). At each sampling point, the plant height, LAI (Delta-T SunScan) and the chlorophyll concentration (Yara N-Tester) were recorded. Plant samples were taken to analyse the content of main nutrients (N, P, K, Mg, Ca and S). The results of plant analysis showed that both fields were in different nutrition status: one in a correct status and another had a complex nutritional deficit (K, Ca and N). Linear regressions and ANOVA proved that under a multiple nutritional deficit, N-Tester readings responded to the growth of the crop, while in the adequate nutritional conditions the sensitivity of N-Tester to the variation in the nitrogen concentration is lower. The relationships between crop parameters and chlorophyll meter readings are not generalisable and thus the interpretation of N-Tester results has to be done separately for each field.

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Using Leaf Chlorophyll Meter to Predict Nitrogen Status and Yield of Grapefruit Trees

HortScience ◽

10.21273/hortsci.31.4.671c ◽

1996 ◽

Vol 31 (4) ◽

pp. 671c-671

Author(s):

Y.C. Li ◽

A.K. Alva ◽

D.V. Calvert ◽

M. Zhang

Keyword(s):

Nutrient Deficiency ◽

Yield Response ◽

Nitrogen Status ◽

Chlorophyll Meter ◽

Leaf Chlorophyll ◽

Irrigation Treatments ◽

N Rates ◽

Spad Readings ◽

Spad Meter ◽

Leaf N

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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Assessing the nitrogen requirements of rice crops with a chlorophyll meter

Australian Journal of Experimental Agriculture ◽

10.1071/ea9941001 ◽

1994 ◽

Vol 34 (7) ◽

pp. 1001 ◽

Cited By ~ 51

Author(s):

FT Turner ◽

MF Jund

Keyword(s):

Growth Stage ◽

Management Practices ◽

N Uptake ◽

Chlorophyll Concentration ◽

Major Influence ◽

Management Tools ◽

Chlorophyll Meter ◽

Before And After ◽

N Management ◽

Spad Meter

Soil and plant analyses to estimate nitrogen (N) fertiliser requirements of rice plants continues to be a research priority because of the major influence of N fertiliser on rice yield, production economics, and concerns regarding excess N in our soil, water, and air. Significant achievements have been made using a portable chlorophyll meter to determine the need for additional N fertiliser. This report summarises recent progress with the Minolta SPAD 502 chlorophyll meter in predicting the need for additional N. The meter does not measure N or chlorophyll concentration; rather it provides immediate, on-site, quantitative measurements of leaf greenness that have been correlated (r2 = 0.62) with rice plant N needs during the 10 days before and after the panicle differentiation growth stage. The SPAD meter measurements taken on the most recently matured leaf can range from 25 to 44 depending on N uptake and growth stage. At SPAD readings >40, additional N fertiliser has not increased yields. It is recognised that SPAD values are influenced by plant growth stage, cultivar, leaf thickness, plant population, and any soil or climate factor causing leaf chlorosis. Users should understand that SPAD values do not indicate how much N to apply, they only indicate the need for additional N. SPAD meter technology does not replace other proven N management practices. However, used in combination with other N management tools, the chlorophyll meter can improve N fertiliser practices for rice.

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Enhancing Visual Quality of Multi-view 360 Video Compression Pipeline

Proceedings of the International Display Workshops ◽

10.36463/idw.2019.0135 ◽

2019 ◽

pp. 135

Author(s):

Junyoung Yun ◽

Hong-Chang Shin ◽

Gwangsoon Lee ◽

Jong-Il Park

Keyword(s):

Video Compression ◽

Visual Quality

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ART-UP: A Novel Method for Generating Scanning-Robust Aesthetic QR Codes

ACM Transactions on Multimedia Computing Communications and Applications ◽

10.1145/3418214 ◽

2021 ◽

Vol 17 (1) ◽

pp. 1-23

Author(s):

Mingliang Xu ◽

Qingfeng Li ◽

Jianwei Niu ◽

Hao Su ◽

Xiting Liu ◽

...

Keyword(s):

State Of The Art ◽

Visual Quality ◽

Qr Code ◽

Quick Response ◽

Estimation Model ◽

Qr Codes ◽

Excellent Performance ◽

Novel Method ◽

Coarse To Fine

Quick response (QR) codes are usually scanned in different environments, so they must be robust to variations in illumination, scale, coverage, and camera angles. Aesthetic QR codes improve the visual quality, but subtle changes in their appearance may cause scanning failure. In this article, a new method to generate scanning-robust aesthetic QR codes is proposed, which is based on a module-based scanning probability estimation model that can effectively balance the tradeoff between visual quality and scanning robustness. Our method locally adjusts the luminance of each module by estimating the probability of successful sampling. The approach adopts the hierarchical, coarse-to-fine strategy to enhance the visual quality of aesthetic QR codes, which sequentially generate the following three codes: a binary aesthetic QR code, a grayscale aesthetic QR code, and the final color aesthetic QR code. Our approach also can be used to create QR codes with different visual styles by adjusting some initialization parameters. User surveys and decoding experiments were adopted for evaluating our method compared with state-of-the-art algorithms, which indicates that the proposed approach has excellent performance in terms of both visual quality and scanning robustness.

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Effect of defocus combined with rotation on the optical performance of trifocal toric IOLs

European Journal of Ophthalmology ◽

10.1177/11206721211002121 ◽

2021 ◽

pp. 112067212110021

Author(s):

Javier Ruiz-Alcocer ◽

Irene Martínez-Alberquilla ◽

Amalia Lorente-Velázquez ◽

José F Alfonso ◽

David Madrid-Costa

Keyword(s):

Visual Quality ◽

Optical Quality ◽

Refractive Errors ◽

Focal Points ◽

Modulation Transfer ◽

Optical Analysis ◽

Toric Intraocular Lens ◽

Toric Iols ◽

Reference Situation

Purpose: To objectively analyze the optical quality of the FineVision Toric intraocular lens (IOL) with two cylinder powers when different combinations of rotations and residual refractive errors are induced. Methods: This study assessed the FineVision Toric IOL with two different cylinder powers: 1.5 and 3.0 diopters (D). Three different rotation positions were considered: centered, 5° and 10° rotated. An optical bench (PMTF) was used for optical analysis. The optical quality of the IOLs was calculated by the modulation transfer function (MTF) at five different focal points (0.0, 0.25, 0.50, 0.75, and 1.00 D). Results: The MTF averaged value of the reference situation was 38.58 and 37.74 for 1.5 and 3.0 D of cylinder, respectively. For the 1.5 D cylinder, the combination of 5° of rotation with a defocus of 0.25, 0.50, 0.75, and 1.0 D induced a decrease on the MTF of 12.39, 19.94, 23.43, 24.23 units, respectively. When induced rotation was 10°, the MTF decrease was 17.26, 23.40, 24.33, 24.48 units, respectively. For the 3.0 D cylinder, the combination of 5° with 0.25, 0.50, 0.75, and 1.0 D of defocus, induced a decrease on the MTF of 12.51, 18.97, 22.36, 22.48 units, respectively. When induced rotation was 10°, the MTF decrease was: 18.42, 21.57, 23.08, and 23.61 units, respectively. Conclusion: For both FineVision Toric IOLs there is a certain optical tolerance to rotations up to 5° or residual refractive errors up to 0.25 D. Situations over these limits and their combination would affect the visual quality of patients implanted with these trifocal toric IOLs.

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