ASSESSMENT THE VISUAL TURFGRASS QUALITY

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3 Centro de Investigação sobre Espaço e Organizações, Faro, Portugal. 4 MedtiBio, Centre for Mediterranean Bioresources and Food, Faro, Portugal. 5Leaf ...

ASSESSMENT THE VISUAL TURFGRASS QUALITY BY REMOTE SENSING TECHNIQUES Guerrero, C1,4; Martins, F.2,3; Lança, R.2; Fernandez, H.2,3; Andrade, R.3; and Pedras, C.M.G.1,5 1 Universidade do Algarve, Faculdade de Ciências e Tecnologia, 2 Instituto Superior de Engenharia 3 Centro de Investigação sobre Espaço e Organizações, Faro, Portugal 4 MedtiBio, Centre for Mediterranean Bioresources and Food, Faro, Portugal 5Leaf, Linking Landscape, Environment, Agriculture and food, Instituto Superior de Agronomia , Lisboa, Portugal

INTRODUCTION: Spatial and temporal variation of soil, climate and plants promote different irrigation requirements which challenge modern agriculture. The maintenance of a golf course represents an agronomic and environmental challenge: where, appearance quality, disease, pests, climatic stresses, nutritional plant status and water deficit are common in golf courses.

HOLE 4 Weather station Sample for NDVI/VARI analysis Irrigation test area

NDVI

Remote sensing technologies can be used to improve site-specific management difficulties. Unmanned aerial vehicles (UAV) can provide valuable data to support decisions of turfgrass managers. The purpose of this study is to assess the visual turfgrass quality by remote sensing techniques, based on Normalized Difference Vegetation Index (NDVI) and Visible Atmospherically Resistant Index (VARI) in different locations of turfgrass areas in a golf course.

VARI

Fig. 5 - NDVI and VARI maps for the hole number 4, 16/03/2015.

STUDY AREA: Location: Royal Golf Course, Vale do Lobo, Portugal (Fig. 1) Coordinate system : N 37o 2.7´ N to N 37o 3.8´; W 8o 2.8´ to W 8o 3.8´ Area of golf course: 32 ha

NDVI

Locations of the evaluated area (Fig.1), holes 4, 13 and 18 Weather station

Soil type: Haplic regosols

Sample for NDVI/VARI analysis Irrigation test area

VARI

Turf species present in each hole : Tees, fairways and roughs : Festuca ruba + Poa pratensis + Lolium perene Greens: Agrostis stolonifera Most of the rainfall occurs concentrated in the winter season. Irrigation is needed during the remaining months of the year to meet the water demand from plants (Fig. 2).

Fig. 6 - NDVI and VARI maps for the hole number 13, 16/03/2015.

HOLE 18 Weather station Sample for NDVI/VARI analysis

4 13 18

Weather stations Rainfall

Fig 1. Location of the Royal Golf Course, Vale do Lobo, Portugal

Max. Temp.

V A RI

N D VI

Rainfall (mm)

Temperature (ºC)

Irrigation test area

Min. Temp.

Fig 2. The maximum and minimum temperature and rainfall in Faro, Portugal.

Fig. 7 - NDVI and VARI maps for the hole number 18, 16/03/2015.

METHODS: The Normalized Difference Vegetation Index (NDVI) and Visible Atmospherically Resistant Index (VARI) maps in the study areas were obtained by using an Unmanned Aerial Vehicle (UAV) with Canon PowerShot SX260HS digital camera equipped with a 12.1 Mpixel with GPS. This collects the information in red (R), green (G) and near infrared (NIR) bands.

Fairway

1.0

Tee

Green

frel

0.8 0.5 0.3 0.0

 NIR   R NDVI   NIR   R

0.55

G   R VARI  G   R   B

0.85 0.55

0.7

0.85 0.55

0.7

0.7

0.85 NDVI

1.0

frel 0.8 0.5 4 0.3

13 18

0.0

Fig 3. The UAV and the camera

0

0.1

0.2

0

0.1

0.2

0

0.1

0.2

VARI

Fig. 8 – Relative frequency of the NDVI and VARI.

RESULTS AND DISCUSSION: CONCLUSIONS:

10.0

Wind (kmh-1)

ET0 (mm)

Km

5.0

0.0 4.0 0

5

10

15

20

Days

25 18 4 13

2.0 0.0 1.4 0 1.2

5

10

15

20

5

10

15

20

Days

1.0 0.8 0 0.6

 The three holes have different microclimates where the exposition to predominant winds play an important role.

18 4 13

Days

In the period, ETo ≈ 1.8 mm day-1 for the hole 18. The micro-climate factor: Km ≈ 0.8 for the hole 4 and Km ≈ 0.9 for the hole 13

Fig. 4 - The wind, Eto and Km

4 25 13

 For the same locations, the VARI and NDVI have similar results according to the health condition of the turfgrass.  The VARI can be a good indicator to evaluate the health condition of the turfgrass and it is cheaper and easily available than the NDVI because it uses only the visible bands.  Further work must be done to continue recording RGB and NIR images from the UAV along the year to assess the plant vigour status of the turfgrass under different weather conditions and use the acquired information to improve irrigation and optimize the water management on the golf course.

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