Special Issue "Spectral Reflectance and Fluorescence Measurements of Crop Performance"

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A special issue of Agriculture (ISSN 2077-0472).

Deadline for manuscript submissions: closed (1 February 2014)

Special Issue Editor

Guest Editor
Dr. Mauricio Hunsche (Website)

Institute of Crop Science and Resource Conservation, Horticultural Science, University of Bonn, Auf dem Huegel 6, 53121 Bonn, Germany

Special Issue Information

Dear Colleagues,

Scientists and growers are aware of the major challenges primary crop production needs to overcome in the next decades: to produce more biomass and food per unit area; to increase the quality of agricultural products; and to reduce costs. All this under consideration of a more rational use of production resources, without disregarding the natural environment. Optical sensors play a key role for improving crop performance in changing environments. In particular, the spectrally resolved reflectance and fluorescence signals enable a fast and precise non-destructive monitoring of biochemical and physiological processes; as often demonstrated in more basic sciences. On the other hand, the demand exists—and the time has come—to use this knowledge for improvement of crop performance in the modern and intensive realm of agriculture.

Under field conditions, crops are exposed to a range of potentially stressful factors, including water and nutrient availability, salinity, as well as atypical temperatures. Moreover, biotic factors drastically constrain achievable yield and quality. In this context, spectral signals and signatures might be recorded, processed and transformed into information to early detect and differentiate single and multiple stresses in order to support a more target-oriented crop management.

Further, interesting applications of spectrally resolved reflectance and fluorescence approaches are found under high-intensive and protected cultivation, such as horticulture. Here, production factors might be optimized to improve growth, yield and product quality—often outside of the ideal cultivation period—and thereby exploiting the genetic potential at maximum. Also, the potential of reflectance and fluorescence techniques as supporting tools for phenotyping and selection of promising genotypes in breeding lines is still underexplored.

This Special Issue of Agriculture covers the following list of major topics, but is not limited to:

  • Sensing and differentiation of stress factors, and their single or combined impact, on the performance of field and horticultural crops.
  • Spatio-temporal changes of the spectral signatures due to biotic and/or abiotic stresses as information basis for precision agriculture.
  • Development, improvement and/or validation of sensors (including those mounted on unmanned aerial vehicles, UAV), spectral indices, or tools for data and image analysis.
  • Detection, characterization and differentiation of plant species (e.g., weeds and major crops), genotypes or physiological stages.
  • Imaging and functioning of plant structures.
  • Estimation of photosynthetic activity, water content, as well as the content and/or composition of plant pigments in leaves and fruits.
  • Phenotyping, identification of functional traits, selection of genotypes in breeding lines.
  • Target-oriented management of production resources (e.g., water, fertilizers, light, agrochemicals) for improved crop performance.
  • Reviews addressing specific issues on the use of spectrally resolved reflectance and fluorescence techniques for improved agricultural production.

Dr. Mauricio Hunsche
Guest Editor

Submission

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. Papers will be published continuously (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are refereed through a peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Agriculture is an international peer-reviewed Open Access quarterly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 300 CHF (Swiss Francs). English correction and/or formatting fees of 250 CHF (Swiss Francs) will be charged in certain cases for those articles accepted for publication that require extensive additional formatting and/or English corrections.

Keywords

  • environmental constraints
  • field and horticultural crops
  • growth and development
  • morpho-physiological and biochemical traits
  • spectral signature
  • stress and dynamic adaptation
  • use of resources
  • yield and quality

Published Papers (8 papers)

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Research

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Open AccessArticle Field Observations with Laser-Induced Fluorescence Transient (LIFT) Method in Barley and Sugar Beet
Agriculture 2014, 4(2), 159-169; doi:10.3390/agriculture4020159
Received: 13 February 2014 / Revised: 18 April 2014 / Accepted: 12 May 2014 / Published: 22 May 2014
Cited by 2 | PDF Full-text (573 KB) | HTML Full-text | XML Full-text
Abstract
The laser-induced fluorescence transient (LIFT) method is a non-invasive remote sensing technique for measurement of photosynthetic performance of plants under laboratory and field conditions. We report here a long-term comparative study to monitor the performance of different cultivars of barley and sugar [...] Read more.
The laser-induced fluorescence transient (LIFT) method is a non-invasive remote sensing technique for measurement of photosynthetic performance of plants under laboratory and field conditions. We report here a long-term comparative study to monitor the performance of different cultivars of barley and sugar beet during the growth season of these crops. The LIFT measurements provided useful results about photosynthetic light use efficiency on selected leaves in the canopy of the studied crops. The different canopy architectures, with different optical properties, influenced the LIFT measurements. Full article
Open AccessArticle Non-Invasive Spectral Phenotyping Methods can Improve and Accelerate Cercospora Disease Scoring in Sugar Beet Breeding
Agriculture 2014, 4(2), 147-158; doi:10.3390/agriculture4020147
Received: 27 March 2014 / Revised: 25 April 2014 / Accepted: 29 April 2014 / Published: 8 May 2014
Cited by 4 | PDF Full-text (615 KB) | HTML Full-text | XML Full-text
Abstract
Breeding for Cercospora resistant sugar beet cultivars requires field experiments for testing resistance levels of candidate genotypes in conditions that are close to agricultural cultivation. Non-invasive spectral phenotyping methods can support and accelerate resistance rating and thereby speed up breeding process. In [...] Read more.
Breeding for Cercospora resistant sugar beet cultivars requires field experiments for testing resistance levels of candidate genotypes in conditions that are close to agricultural cultivation. Non-invasive spectral phenotyping methods can support and accelerate resistance rating and thereby speed up breeding process. In a case study, experimental field plots with strongly infected beet genotypes of different resistance levels were measured with two different spectrometers. Vegetation indices were calculated from measured wavelength signature to determine leaf physiological status, e.g., greenness with the Normalized Differenced Vegetation Index (NDVI), leaf water content with the Leaf Water Index (LWI) and Cercospora disease severity with the Cercospora Leaf Spot Index (CLSI). Indices values correlated significantly with visually scored disease severity, thus connecting the classical breeders’ scoring approach with advanced non-invasive technology. Full article
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Open AccessArticle Salinity-Induced Changes of Multiparametric Fluorescence Indices of Tomato Leaves
Agriculture 2014, 4(2), 132-146; doi:10.3390/agriculture4020132
Received: 11 January 2014 / Revised: 22 April 2014 / Accepted: 22 April 2014 / Published: 30 April 2014
Cited by 1 | PDF Full-text (778 KB) | HTML Full-text | XML Full-text
Abstract
The aim of our study was to identify appropriate multiparametric fluorescence ratios to evaluate the response of tomato (Solanum lycopersicum) genotypes to salinity. In this context, we hypothesized that the fluorescence indices BFRR_UV, FLAV, NBI and SFR provided by the [...] Read more.
The aim of our study was to identify appropriate multiparametric fluorescence ratios to evaluate the response of tomato (Solanum lycopersicum) genotypes to salinity. In this context, we hypothesized that the fluorescence indices BFRR_UV, FLAV, NBI and SFR provided by the multiparametric fluorescence technique reveal the impact of salinity on tomato leaves. For this purpose, the tomato genotypes H-2274, Harzfeuer and Rio Grande were grown in the greenhouse under standard or saline conditions. As reference measurements, we recorded the maximum photochemical efficiency of photosystem II (Fv/Fm) via pulse-amplitude-modulated (PAM) chlorophyll fluorescence (ChlF) and analyzed the concentrations of sodium (Na), potassium (K), magnesium (Mg), proline and chlorophyll (Chl). In general, “Harzfeuer” showed a more pronounced response to salinity, as revealed by the increase in Na and proline as well as the decrease in K concentration. Significant differences between the control and the salt treatment were also assessed with Fv/Fm. The ratios BFRR_UV, FLAV, SFR_G and NBI_G increased significantly in the salinity-exposed plants. These ratios, compared with Fv/Fm, also provide precise but more rapid information about the impact of salinity on tomato leaves. On this basis, we demonstrate that the multiparametric fluorescence indices provide a valuable, rapid and practical tool for the in situ monitoring of the physiological status of plants exposed to salinity. Full article
Open AccessArticle Crop Dominance Mapping with IRS-P6 and MODIS 250-m Time Series Data
Agriculture 2014, 4(2), 113-131; doi:10.3390/agriculture4020113
Received: 6 January 2014 / Revised: 19 March 2014 / Accepted: 14 April 2014 / Published: 25 April 2014
Cited by 3 | PDF Full-text (1704 KB) | HTML Full-text | XML Full-text
Abstract
This paper describes an approach to accurately separate out and quantify crop dominance areas in the major command area in the Krishna River Basin. Classification was performed using IRS-P6 (Indian Remote Sensing Satellite, series P6) and MODIS eight-day time series remote sensing [...] Read more.
This paper describes an approach to accurately separate out and quantify crop dominance areas in the major command area in the Krishna River Basin. Classification was performed using IRS-P6 (Indian Remote Sensing Satellite, series P6) and MODIS eight-day time series remote sensing images with a spatial resolution of 23.6 m, 250 m for the year 2005. Temporal variations in the NDVI (Normalized Difference Vegetation Index) pattern obtained in crop dominance classes enables a demarcation between long duration crops and short duration crops. The NDVI pattern was found to be more consistent in long duration crops than in short duration crops due to the continuity of the water supply. Surface water availability, on the other hand, was dependent on canal water release, which affected the time of crop sowing and growth stages, which was, in turn, reflected in the NDVI pattern. The identified crop-wise classes were tested and verified using ground-truth data and state-level census data. The accuracy assessment was performed based on ground-truth data through the error matrix method, with accuracies from 67% to 100% for individual crop dominance classes, with an overall accuracy of 79% for all classes. The derived major crop land areas were highly correlated with the sub-national statistics with R2 values of 87% at the mandal (sub-district) level for 2005–2006. These results suggest that the methods, approaches, algorithms and datasets used in this study are ideal for rapid, accurate and large-scale mapping of paddy rice, as well as for generating their statistics over large areas. This study demonstrates that IRS-P6 23.6-m one-time data fusion with MODIS 250-m time series data is very useful for identifying crop type, the source of irrigation water and, in the case of surface water irrigation, the way in which it is applied. The results from this study have assisted in improving surface water and groundwater irrigated areas of the command area and also provide the basis for better water resource assessments at the basin scale. Full article
Open AccessArticle Advanced Multi-Color Fluorescence Imaging System for Detection of Biotic and Abiotic Stresses in Leaves
Agriculture 2014, 4(2), 79-95; doi:10.3390/agriculture4020079
Received: 30 January 2014 / Revised: 20 March 2014 / Accepted: 25 March 2014 / Published: 4 April 2014
Cited by 6 | PDF Full-text (2210 KB) | HTML Full-text | XML Full-text
Abstract
The autofluorescence of a sample is a highly sensitive and selective optical property and gives the possibility to establish non-destructive techniques of the investigation of plants, like detecting the chlorophyll fluorescence related to stress phenomena. In this study, an advanced multi-color fluorescence [...] Read more.
The autofluorescence of a sample is a highly sensitive and selective optical property and gives the possibility to establish non-destructive techniques of the investigation of plants, like detecting the chlorophyll fluorescence related to stress phenomena. In this study, an advanced multi-color fluorescence imaging system and data analysis were presented. The advantage of an imaging system is the additional receiving of spatial information over a sample area, this is a strong improvement compared to spot measurements commonly used. The purpose was to demonstrate the possibility of the detection and characterization of stress symptoms using this system. Specific fluorescence ratios were identified to characterize the stress status over the whole leaf, here shown on barley grown under different nitrogen supply (abiotic stress). Due to the changes, it is possible to make conclusions about leaf pigments (chlorophylls and phenolics) related to stress response. The second aim was to use the shape of local symptoms (biotic stress) as a criterion. For this purpose, three structural different kinds of fungal symptoms were analyzed using shape descriptors. It shows that an additional image shape analysis can be very useful for extracting further information, in this case the successful discrimination of fungal infections. Full article
Open AccessArticle Evaluation of Spring Wheat (20 Varieties) Adaptation to Soil Drought during Seedlings Growth Stage
Agriculture 2014, 4(2), 96-112; doi:10.3390/agriculture4020096
Received: 22 January 2014 / Revised: 22 March 2014 / Accepted: 26 March 2014 / Published: 4 April 2014
PDF Full-text (275 KB) | HTML Full-text | XML Full-text
Abstract
The effect of soil drought (10 days) on the growth of plants, the accumulation of water and leakage of electrolytes, gas exchange, the contents of chl a + b and carotenoids in leaves and photochemical activity of photosystem II was studied at [...] Read more.
The effect of soil drought (10 days) on the growth of plants, the accumulation of water and leakage of electrolytes, gas exchange, the contents of chl a + b and carotenoids in leaves and photochemical activity of photosystem II was studied at the seedling stage by transient fluorescent analysis in 20 of the popular varieties of polish spring wheat. Drought caused a particularly strong reduction in vigor of growth of seedlings, net photosynthesis rate and triggered an increase in electrolyte leakage from the leaves. Certain varieties during the drought demonstrated relatively intense CO2 assimilation at low water loss through transpiration. The varieties tested were significantly different in terms of tolerance to drought of the processes of gas exchange and seedlings development. Photochemical processes in PSII showed high tolerance to drought and at the same time low differentiation among varieties. The results obtained suggested that tolerance of growth parameters to drought and CO2 assimilation at the seedling stage may alleviate consequent depression of final yield of the grain. Full article
Open AccessArticle Fluorescence Indices for the Proximal Sensing of Powdery Mildew, Nitrogen Supply and Water Deficit in Sugar Beet Leaves
Agriculture 2014, 4(2), 58-78; doi:10.3390/agriculture4020058
Received: 15 January 2014 / Revised: 12 February 2014 / Accepted: 13 March 2014 / Published: 28 March 2014
Cited by 5 | PDF Full-text (935 KB) | HTML Full-text | XML Full-text
Abstract
Using potted sugar beet plants we aimed to investigate the suitability of four fluorescence indices to detect and differentiate the impact of nitrogen supply, water deficit and powdery mildew in two sugar beet cultivars (Beta vulgaris L.). Plants were grown inside [...] Read more.
Using potted sugar beet plants we aimed to investigate the suitability of four fluorescence indices to detect and differentiate the impact of nitrogen supply, water deficit and powdery mildew in two sugar beet cultivars (Beta vulgaris L.). Plants were grown inside a polytunnel under two nitrogen levels combined with water deficit or full irrigation. Changes in plant physiology were recorded at two physiological stages with a multiparametric handheld fluorescence sensor and a fluorescence imaging system. The analysis of chlorophyll content and osmotic potential served as reference. Based on our results, the fluorescence indices “Nitrogen Balance Index” and “Simple Fluorescence Ratio” responded quite sensitively to drought stress and mildew infection. Moreover, the blue-to-far-red fluorescence ratio revealed significant stress-induced alterations in the plant physiology. In all, fluorescence indices might be used as single or combined indices for successful stress sensing. However, a robust stress differentiation by using only one fluorescence ratio could not be accomplished. Full article

Review

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Open AccessReview Hyperspectral and Chlorophyll Fluorescence Imaging for Early Detection of Plant Diseases, with Special Reference to Fusarium spec. Infections on Wheat
Agriculture 2014, 4(1), 32-57; doi:10.3390/agriculture4010032
Received: 7 February 2014 / Revised: 11 March 2014 / Accepted: 17 March 2014 / Published: 24 March 2014
Cited by 11 | PDF Full-text (1357 KB) | HTML Full-text | XML Full-text
Abstract
In recent years, market pressures have reinforced the demand to solve the problem of an increased occurrence of Fusarium head blight (FHB) in cereal production, especially in wheat. The symptoms of this disease are clearly detectable by means of image analysis. This [...] Read more.
In recent years, market pressures have reinforced the demand to solve the problem of an increased occurrence of Fusarium head blight (FHB) in cereal production, especially in wheat. The symptoms of this disease are clearly detectable by means of image analysis. This technique can therefore be used to map occurrence and extent of Fusarium infections. From this perspective, a separate harvest in the field can be taken into consideration. Based on the application of chlorophyll fluorescence and hyperspectral imaging, characteristics, requirements and limitations of Fusarium detection on wheat, both in the field and in the laboratory, are discussed. While the modification of spectral signatures due to fungal infection allows its detection by hyperspectral imaging, the decreased physiological activity of tissues resulting from Fusarium impacts provides the base for CFI analyses. In addition, the two methods are compared in view of their usability for the detection of Fusarium, and different approaches for data analysis are presented. Full article
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