Comparing a chromameter and a hand held NDVI meter to predict nitrogen and water content of turfgrass

Year 2020, Volume: 25 Issue: 1, 57 - 64, 06.04.2020

Muharrem Keskin , Cagatay Cam Yunus Emre Sekerli

https://doi.org/10.37908/mkutbd.646974

Cited By: 1

Abstract

Aims:
Nitrogen content (NC) and water content
(WC) of turfgrass is traditionally determined by laboratory analysis which is
time-consuming, tiresome, laborious and costly. The aim of this study was to
examine the suitability of two hand held optical instruments (GreenSeeker NDVI
meter and chromameter) to evaluate NC and WC of turfgrass.

Methods and Results:
Six turfgrass plots of 1 m x 1 m with a
mixture of five different species were used and variable rate nitrogen
fertilizer (N₀: 0 g N m^-2, N₁: 2.5 g N m^-2,
N₂: 5 g N m^-2) was applied. NDVI measurements were taken
at around noon with a GreenSeeker NDVI instrument from the plots. After mowing,
the color values of the clippings were measured using a hand-held chromameter.
The data were analyzed using correlation and partial least square regression
(PLSR). A high correlation was found between leaf NC, WC, NDVI and color
values. The leaf NC (%) can be estimated from the NDVI (R²val=0.73,
SEP=0.19%) and color values (L*a*b*C*h°) (R²val=0.76; SEP=0.18%).
Also, it was found that the WC (%) can be predicted from the NDVI (R²val=0.40,
SEP=5.07%) and color values (L*C*h°) (R²val=0.69; SEP=3.67%) with
slightly lower accuracy.

Conclusions:
Turfgrass leaf NC can be estimated with
either an NDVI instrument (R²=0.73, SEP=0.19%) or a chromameter (R²=0.76,
0.18%) with reasonable accuracy in a more objective and economical way.

Significance and Impact of
the Study: Considering
the reduction in time and cost required in the NC and WC analysis, we think
that results of this study may be useful for turf field managers. Also,
nitrogen determination with sensors will be a more eco-friendly way if used by managers.

Keywords

Turfgrass, remote sensing, nitrogen content, water content, NDVI meter, chromameter

Thanks

The authors would like to thank Dr. Berkant ODEMIS and Dr. Yurtsever SOYSAL for their support. Also they thank Aysel ARSLAN and Mustafa AKKAMIS for their assistance.

Çim bitkisinin azot ve su içeriği tahmini için Renk ölçer ve NDVI ölçerin karşılaştırılması

Abstract

Amaç: Geleneksel olarak çim bitkisinin azot
(Aİ) ve su içeriği (Sİ) tahmini zaman alıcı, yorucu, fazla iş gücü gerektiren
ve masraflı olan kimyasal laboratuvar analizleriyle belirlenmektedir. Bu
çalışmanın amacı, iki farklı el tipi optik algılayıcının (GreenSeeker NDVI
metre ve renk ölçer) çim bitkisinin azot ve su içeriğini değerlendirmedeki
uygunluğunu incelemektir.

Yöntem ve Bulgular: Çalışmada 1 m x 1 m'lik altı adet çim
parselinde değişken düzeyli azotlu gübre uygulaması yapılmıştır. NDVI ölçümleri
arazide el tipi GreenSeeker NDVI ölçer ile gerçekleştirilmiştir. Biçme
işleminden sonra, çim biçkilerinin renk değerleri laboratuvarda renk ölçer
kullanılarak ölçülmüştür. Veriler korelasyon ve kısmi en küçük kareler
regresyon (PLSR) analizi kullanılarak değerlendirilmiştir. Yaprak Aİ, Sİ ile
NDVI ve renk değerleri arasında yüksek korelasyon bulunmuştur. Yaprak Aİ
(%)’nin NDVI (R²val=0.73, SEP=% 0.19) ve renk değerlerinden
(L*a*b*C*h°) (R²val=0.76; SEP=% 0.18) tahmin edilebileceği
tepit edilmiştir. Ayrıca, Sİ (%)’nin NDVI (R²val=0.40,
SEP=% 5.07) ve renk değerlerinden (L*C*h°) (R²val=0.69;
SEP=3.67 %) daha düşük doğruluk ile tahmin edilebileceği belirlenmiştir.

Genel Yorum: Sonuç olarak; çim yaprağı Aİ’nin, NDVI
cihazı veya renk ölçer kullanılarak daha objektif ve ekonomik bir şekilde makul
hassasiyet ile tahmin edilebileceği tespit edilmiştir.

Çalışmanın Önemi ve Etkisi: Azot ve su içeriği analiz süresindeki
azalma dikkate alındığında, çalışma sonuçlarının çim saha bakım sorumluları
için faydalı olacağı değerlendirilmiştir. Ayrıca algılayıcılar ile yapılacak azot
içeriği tespitinin çim alan bakım sorumluları tarafından kullanılması halinde
daha çevre dostu bir yöntem olacağı düşünülmektedir.

Keywords

Çim, uzaktan algılama, azot içeriği, su içeriği, NDVI ölçer, renk ölçer

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