Evaluating spectral indices for winter wheat health status monitoring in Bloemfontein using Lsat 8 data

Mashaba, Zinhle; Chirima, George; Botai, Joel Ongego; Combrinck, Ludwig; Munghemezulu, Cilence

doi:10.4314/sajg.v5i2.10

Cited by 3 publications

(2 citation statements)

References 44 publications

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“…The presence of many downward "spikes" that exist below 40 Wh is indicative of cloud movement, which impacts severely on the yield of output power for all three tilt angles. Bloemfontein is a summer rainfall area with less cloud movement during the winter months [28]. This is confirmed in Figure 7 where only one significant downward "spike" is evident on 14 June 2016, with no other interruptions in direct beam radiation visible between 17 May and 23 July 2016.…”

Section: Resultsmentioning

confidence: 53%

Optimum Tilt Angles for PV Modules in a Semi-Arid Region of the Southern Hemisphere

Hertzog¹,

Swart²

2018

IJET

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It is essential to repeat a test of a given construct in research in order to underpin knowledge, support validity and enable its application in other contexts. The purpose of this article is to present repetitive test results validating the optimum tilt angle of a stationary PV module that was installed in a semi-arid region of South Africa. An experimental design incorporating a two-year longitudinal study is used. The results for 2016 and 2017 reveal that a PV module with a tilt angle of Latitude plus 10° yielded the highest output power for winter months, while a PV module with a tilt angle of Latitude minus 10° yielded the highest output power for summer months. However, for both years, a tilt angle set to the Latitude angle of the installation site yielded the highest overall average output power (60.02 Wh per day). It is therefore recommended to install stationary PV modules at a tilt angle equal to the Latitude of the installation site for a semi-arid region in the southern hemisphere.

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Section: Resultsmentioning

confidence: 53%

Optimum Tilt Angles for PV Modules in a Semi-Arid Region of the Southern Hemisphere

Hertzog¹,

Swart²

2018

IJET

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“…On the other hand, lower NDVI values may indicate weaker photosynthetic activity and overall poorer vegetation health, due to likely unfavorable growing conditions (e.g., water stress, exposure to herbicide). The NDVI is typically used as indicator to monitor ecosystem health (e.g., Bento et al 2018;Flores-Cardenas et al 2018;Mariano et al 2018) and crop phenology (e.g., Mashaba et al 2016;Martin and Latheef 2017;Inurreta-Aguirre et al 2018). A number of studies (e.g., Thelen et al 2004;Dicke et al 2012;Lewis et al 2014;Prakash et al 2017) have demonstrated that NDVI is an effective index in detecting herbicide damage on plants.…”

Section: Remote Sensing Datamentioning

confidence: 99%

Remote‐sensing Based Assessment of Long‐term Riparian Vegetation Health in Proximity to Agricultural Lands with Herbicide Use History

Yousef

Gebremichael

Ghebremichael

et al. 2019

Integr Envir Assess & Manag

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Riparian ecosystems provide various ecosystem services including habitat for a variety of plant and animal communities, biofiltering, and stabilizing stream and river systems. Due to their location, riparian zones often share long borders with agricultural fields where herbicides are commonly applied to eliminate unwanted plants. There is a general concern that exposure of riparian vegetation to off‐target drifted herbicides may adversely impact their health and diversity. We utilized the Normalized Difference Vegetation Index (NDVI) to investigate the long‐term (between 1992 and 2011) trend of riparian vegetation health at 17 locations in the Midwest and Great Plains areas of the United States, where herbicide usage was likely most intense. Assessment of NDVI data demonstrated that long‐term vegetation health did not decline for the studied riparian zones located in proximity to croplands during spring months (April and May). During summer (June and July), while the long‐term vegetation health did not decline for the majority of the sites, there were a few cases in Kansas and Nebraska with a decline in vegetation health (negative‐trending NDVI). Cluster analysis of the negative‐trending NDVI pixels showed that the majority of these pixels were randomly distributed throughout these riparian sites, indicating a lack of shared common causing factors. Similarly, proximity analysis suggested that distance from croplands was not associated with the decline of vegetation health found in these sites, suggesting that exposure to herbicide drift may not be a plausible factor because this would have shown higher impact on pixels closer to the cropland. Changes in canopy coverage and vegetation diversity also did not show any dependence on distance from croplands. Finally, the remote‐sensing–based NDVI data sets used provide only an indirect way of assessing the impact of herbicide drift, and therefore, further work based on field survey data is recommended to completely isolate the impacts of herbicides. Integr Environ Assess Manag 2019;15:528–543. © 2019 The Authors. Integrated Environmental Assessment and Management published by Wiley Periodicals, Inc. on behalf of Society of Environmental Toxicology & Chemistry (SETAC)

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METHODS OF DETECTION OF DISEASES ON WHEAT CROPS ACCORDING TO REMOTE SENSING (overview)

Dubrovskaya

Гурова

Пестунов

et al. 2019

Sib. vestn. s-h. nauki

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Nowadays multi- and hyperspectral data of remote sensing is widely used in many countries worldwide for agricultural lands monitoring. The issue of their application for detection and assessment of infestation of agricultural crops, damage from diseases and weeds is understudied both in Russia and abroad. Early detection and accurate diagnosis of various wheat diseases are key factors in crop production, contributing to the reduction of qualitative and quantitative crop losses, as well as improving the effectiveness of protective measures. The paper presents a review of up-to-date methods for detecting diseases and assessing the extent of crop damage by remote sensing of wheat using optical imaging systems, the most promising of which is hyperspectral imaging equipment. The identification spectra of healthy plants and the ones with signs of damage from the main fungal diseases as well as the correlation of spectra with the degree of damage are shown. To be able to effectively use the results of diagnostics and detection of diseases, the informational value of the spectral indices of vegetation in the detection of diseases is presented. A table of vegetation indices is given, calculated from the values of reflection coefficients in wide and narrow spectral ranges when determining wheat diseases. The use of optical methods in the monitoring of the main fungal diseases of wheat will accurately identify lesions of crops, reliably diagnose diseases and the extent of plant damage from diseases, and thereby provide support to agricultural producers in decision-making on timely and effective crop protection measures. The results of the review will be used to develop digital technology of early detection and lesion focalization of spring wheat and other agricultural crops.

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Evaluating spectral indices for winter wheat health status monitoring in Bloemfontein using Lsat 8 data

Abstract: Monitoring wheat growth under different weather and ecological conditions is vital for

Cited by 3 publications

References 44 publications

Optimum Tilt Angles for PV Modules in a Semi-Arid Region of the Southern Hemisphere

Optimum Tilt Angles for PV Modules in a Semi-Arid Region of the Southern Hemisphere

Remote‐sensing Based Assessment of Long‐term Riparian Vegetation Health in Proximity to Agricultural Lands with Herbicide Use History

METHODS OF DETECTION OF DISEASES ON WHEAT CROPS ACCORDING TO REMOTE SENSING (overview)

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