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22Journal of Siberian Federal University. Engineering & Technologies, 2019, 12(5), 617-622
yflK 528.855
Using Ground-Based Spectrometry for Operational Monitoring of Crop Yields
Anatoly P. Shevyrnogov, Irina Yu. Botvich and Tamara I. Pisman*
Institute of Biophysics SB RAS FRC «Krasnoyarsk Science Center SB RAS» 50/50 Akademgorodok, Krasnoyarsk, 660036, Russia
Received 24.06.2019, received in revised form 02.07.2019, accepted 09.07.2019
The purpose of this study is to analyze the relationship between crop yields and total chlorophyll potential of different barley and oats cultivars. For this purpose, we used the spectra of grain crops obtained from ground-based remote sensing, and laboratory data. Ground-based data were obtained at the experimental fields located in the Krasnoyarskii Krai. Experiments were carried out in different seasons and under various lighting conditions. Spectral measurements were done with a double-beam spectrophotometer. It was installed on the mobile work platform at heights of 5 to 18 m. The study showed good correlation between crop yields and total chlorophyll potential for barley and oats cultivars.
Keywords: ground remote sensing, yield, total chlorophyll potential, barley, oats.
Citation: Shevyrnogov A.P., Botvich I.Yu., Pisman T.I. Using ground-based spectrometry for operational monitoring of crop yields, J. Sib. Fed. Univ. Eng. technol., 2019, 12(5), 617-622. DOI: 10.17516/1999-494X-0161.
Применение наземного спектрометрирования для оперативного мониторинга урожайности сельскохозяйственных культур
А.П. Шевырногов, И.Ю. Ботвич, Т.И. Письман
Институт биофизики СО РАН ФИЦ «Красноярский научный центр СО РАН» Россия, 660036, Красноярск, Академгородок, 50/50
Целью данного исследования является анализ связи между урожайностью и суммарным хлорофилльным потенциалом посевов ячменя и овса. Для этого были использованы спектры
© Siberian Federal University. All rights reserved
This work is licensed under a Creative Commons Attribution-NonCommercial 4.0 International License (CC BY-NC 4.0). Corresponding author E-mail address: ap_42@mail.ru, irina.pugacheva@mail.ru
*
зерновых культур, полученные при наземном дистанционном зондировании, и лабораторные данные. Наземные данные были получены на экспериментальных полях, расположенных в Красноярском крае. Эксперименты проводились в разные сезоны, при различных условиях освещения. Спектральные измерения осуществляли с использованием двухлучевого спектрорадиометра. Он был установлен на подвижной платформе на высоте от 5 до 18 м. Проведенноеисследование показалохорошуюкорреляциюмеждуурожайностъю исуммарным хлорофилльным потенциалом для различных сортов ячменя и овса.
Ключевые слова: наземное дистанционное зондирование, урожайность, суммарный хлорофилльный потенциал, ячмень, овес.
Introduction
Remote sensing techniquesare aneffective tool of monitoring farmcrops[l], Toevaluate the; yields of farm croeh by remote sensong lechniques,thepeanOs needtnbncontineouslymoeiitorednur-ing their growing soason. Roliablemonstocing shonOnbebused ontheaeopdata with a relativity Oiah temporal resolulioo (eveqe h-R daytl. PosametersehaeaeterieOogthepliytiologis;q stateof SIo .lenlt (yield) during their growing season should be evaluated quickly [2].
The classical method of evaluating the state of the crops is based on NDVI [3]. In this research they evaluatedtiieuse o( theMODIaNDVtandnurfnco-emperatnteproducts to dovelop a multidimensional regressing ahjorithmto gne diet; t°e slete ahucounIyleveiqlelyt.
The NDVItaotooal h^y^a:o^le sss repsesenitotiveoferoo eaowthnndniomqin ehypgeianpohnamai data is repreterto-no el tte orea moisture stress condition [4]. Vegetation indices are usually calculated by using plant reflectance at two wavelengths. Ground - based measurements are necessary for decoding and interpreting the data obtained from satellites [5].
The purpose of this study was to investigate the relationship between crop yields and total chlorophyll potential of arley and oats based on reflectance spectra obtained by ground - based remote measurements.
Material and methods
Barley (Horde disticxon L.) and oats (Avena sativa L.) crops were investigated in this study. These crops differ in their grain yield, chlorophyll content, and time to maturity. They are commonly grown in Russia, and their physiology has been sufficiently studied.
Field stu&eswere performed 001 fieklssituated intlio ehnIeat£o-° swutiietnnegbns aq the Krasna-yarskii Krai (Rusela) durioo tteyrowiny sehsoneofbetween2002ang2hlh.T0e ttuches woe conduntee on 200 - 600 m2experimegtalRSots.The plnlsaifforeilin the amounts of fertilizers added to the soil per square meter [6]. The pletnwere-ocaieO re-Ren do(etooach other,i.e. In thesme cilmeticcohdiS(ogs.
The calculation of total chlorophyll potential was based on registration of the reflectance factor, px, of the crops using a PDSP double-beam spectrophotometer installed on the elevated work platform at heights of otol8munhe rsgnnyooh0itiohs [7].
To assess the cnop yielde at the end of the growing season used the total cMorophyll potential (equation 1).
ZS(t) = j 90.((0 + P55o(0)- t)dX
dt, (1)
where 90 is the multiplier equal to the half - width of the chlorophyll absorption band between 550 and 730 nm, p550 andp730 arevalues of thereflectance factor of the plantcanopy ath = 550 nm and l = 730 nm.
The yields of barley and oats on the study plots were determined by weighing the grains collected from 2 m2 simultaneously with the remote measurements of the reflectance factor.
Reauatsand doscuasien
Var iations in the reflectance factor of oats and barley crops over the growing season are shown in Fig.l and Fig. 2.
As plants developed, their color changed from bright green in the early phase of development (June) to bright yellow at the end of the growing season (August). In the early phase of plant devel-
Fig. 1. Spectral reflectance characteristics throughout the growing season of oats
Fig. 2. Spectral reflectance characteristics throughout the growing season of barley
opment, plant reflectance factor had two distinct minima at 400 nm and 680 nm. The values of the reflectance factor could reach 60-65% at 800 nm and 20-25% at 550 nm, while at 400 nm and 680 nm, they varied between 4 and 8% (Fig. 1 and Fig. 2). In middle of July the crops differed in their optical properties and the amounts of pigments in plants. As plants developed, their vegetative biomass built up, and the reflectance factor in the region between 620 and 730 nm increased. That was caused by the chlorophyll decrease in the crops. Both crops showed similar variations in the values of the reflectance factor, but they differed in the values of absorption of radiant energy in the green and near - infrared regions. The reflectivity of barley was higher than the reflectivity of oats in the near-infrared spectral region (X = 730 - 810 nm). In that period, the pigment ratios changed rapidly, and ear development consumed the assimilates. The reflectance factor in the red region (680-730 nm) increased at a higher rate than the reflectance factor in the shortwave region (400-460 nm). By the end of the growing season, the plants had turned completely yellow, the grain in the ears had ripened, andthere wasalmost no chlo rophyllin theplants.Analysis of the; spectra showed that in that phaso, reflectance factors rn thewaveknghhcani^ betweec^Oand 7r0 nm hail changed more substantial^ then °n elher phasesonlhegrowinc senaonandlhal ftey wcraessepOia°lc dirermined by the amounfc of nigmenta (total chlorophol ll in hheplante(tPered anaofptinnspectram ad chlorophyll "a'' Vm„= 6ef nm). The! waemainly caused by intense processes of accumulation and breakdown in plants, whichmao he usedasiodlmaaafa oechanrecoecurnina inlhem.Barley has shorter time to mnturity(Fth. ll. lhan oels rFia. OX aad chloronhyltbreoaaowocn lhe natplantsio the red absorptioo opectram (S = 68S nm) is 8iiy days dalaysd comparel tobatlero T(ius.seaaonal variations in tOmrpflectancefeptof, /e,of ihecropucay de used teidentifcn)ahlspefipsahn evaluate the physiologlGao stntcof tUe y!ants.
Invettinatienr pf eorrdatiant be(weeo[ tle oieldof bprleyarp a aoe ceopsandtotr) ehloroohyll potential w erebasedan loIlg-iermda(auo croptgrown on oods couSainingvaeious amountsoafertilizers. To obtainaccureteann relranieeclimytes cetheseparame(era,thruwercmecsured and calculated for ten years, under different growing conditions. Results of these investigations are shown in Fig. 3. The
Oat crop: y = 0.002x- 0,215 R2 = 0,743 A
■ J— Barley crop: y = 0.000x+ 0,140 R2 = 0.793
x ■
■ ■ ■
■ Oat crop Barley crop
100 125 150 175 200 225 250 275 300
SS(t)
Fig. 3. Relationship between the crop yield and total chlorophyll potential of oats (based on the data for 17 fields) and barley (basedon thedata for 58 fields)duringthe growingseason
value of total chlorophyll potential for barley is higher than its value for oats with yield contents being equal because of physiological differences between the crops. Barley leaves are broader than oats leaves, and during the active growing phase, the leaf area density of barley is higher than the leaf area density of oats.
Measurements showed good correlation between yield and total chlorophyll potential for barley and oat crops cultivated under different sowing and growing conditions. For barley crops, the coefficient of determination is R2 = 0.79 and for oat crops R2 = 0.74. However, correlation between chlorophyll potential and chlorophyll content of barley and oats crops is higher than correlation between total chlorophyll potential and crop yield [7]. Correlations obtained for one season with optimal plant growing conditions are higher than the average correlations based on the data obtained for ten years, as the crops were grown under dissimilar weather conditions. This correlation is indicating that reliable estimates of crop yield can be obtained by determining chlorophyll potential by the optical remote sensing method.
Conclusion
The study showed the effectiveness of using ground - based remote sensing to estimate yield of barley and oats crops based on the total chlorophyll potential calculated from the reflectance factor, pk. The effectiveness of the method was proved by a large number of field remote measurements and laboratory measurements. Monitoring of changes in the reflectance factor of barley and oat crops over the growing season showed their high information value in the region between 550 and 730 nm. This spectral range can be used to decode aerospace multispectral images [8, 9]. Ground-based remote measurements of the reflectance factors of barley and oat crops suggest the following conclusions.
The main results:
1. The study showed good correlation between crop yields and total chlorophyll potential for different varieties of barley and oats. The coefficient of determination for barley is R2= 0.79 and for oats R2 = 0.74.
2. The value of total chlorophyll potential for barley is higher than its value for oats with yield contents being equal.
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