Zemdirbyste-Agriculture, vol. 100, No. 1 (2013), p. 81–90
UDK 633.15:631.67:520.84 / DOI 10.13080/z-a.2013.100.011
Determination of water stress with spectral reflectance on sweet corn (Zea mays L.) using classification tree (CT) analysis
Levent GENC, Melis INALPULAT, Unal KIZIL, Mustafa MIRIK, Scot E. SMITH, Mehmet MENDES
Water stress is one of the most important growth limiting factors in crop production. Several methods have been used to detect and evaluate the effect of water stress on plants. The use of remote sensing is deemed particularly and practically suitable for assessing water stress and implementing appropriate management strategies because it presents unique advantages of repeatability, accuracy, and cost-effectiveness over the ground-based surveys for water stress detection. The objectives of this study were to 1) determine the effect of water stress on sweet corn (Zea mays L.) using spectral indices and chlorophyll readings and 2) evaluate the reflectance spectra using the classification tree (CT) method for distinguishing water stress levels/severity. Spectral measurements and chlorophyll readings were taken on sweet corn exposed to four levels of water stress with 0, 33, 66 and 100 % of pot capacity (PC) before and after each watering time. The results demonstrated that reflectance in the red portion (600–700 nm) of the electromagnetic spectrum decreased and increased in the near infrared (NIR) region (700–900 nm) with the increasing field capacity of water level. Reflectance measured before the irrigation was generally higher than after irrigation in the NIR region and lower in the red region. However, when the four levels of PC and before or after irrigation only were compared, reflectance spectra indicated that water stressed corn plants absorbed less light in the visible and more light in the NIR regions of the spectrum than the less water stressed and unstressed plants. There was a similar trend to reflectance behaviour of water stress levels using chlorophyll readings that decreased over time. The CT analysis revealed that water stress can be assessed and differentiated using chlorophyll readings and reflectance data when transformed into spectral vegetation indices.
Key words: classification tree, spectral reflectance, water stress, Zea mays.
Full text: 100_1_str11.pdf