Eyad Al-Khaled* ⁽¹⁾ Yousef Nemr ⁽²⁾ and Iman Alhumaer⁽³⁾

(1). General Organization of Remote Sensing (GORS), Damascus, Syria.

(2). Crops Field Department, Damascus University, Damascus, Syria.

(3). Planning and International Cooperation, Ministry of Agriculture and Agrarian Reform (MAAR), Damascus, Syria.

(*Corresponding author: Dr. Eyad Al-Khaled. E.Mail. dr.eyadalkhaled@gmail.com).

Received: 09/09/2016                                 Accepted: 16/10/2016

Abstract

A field experiment was conducted at the General Organization of Remote Sensing (GORS), Damascus countryside, Syria, during 2013/2014 season, using some spectral indices i.e. NDVI, SRI, EVI, NDVI₇₀₅, mSR₇₀₅, mNDVI₇₀₅, to determine the spectral response of wheat plant throughout its different developing stages under the effect of irrigation and nitrogen fertilization, also using spectral indices in predicting yield, and study the correlation between the spectral indices, and some vegetative and productivity characteristics. The FieldSpecPro RS3 was used to record the radiometric characteristics, each 15 days, also some vegetation indices were recorded (Leaf Area Index LAI, fresh and dry weight, and chlorophyll content in leaves), starting from the beginning to the end of plant growth, besides the yield and yield components at harvest. It was noticed that the performance of all spectral indices was similar, they were low at the beginning of plant growth, then increased to reach their maximum values at the vegetative stage, then decreased again with the development of plant growth and harvest. Nitrogen fertilizer showed a significant effect on spectral indices at the first plant stages, N₀ gave the lowest values, while N₁, N₂, and N₃ gave a highest value. In terms of irrigation levels (I₁, I₂, and I₃), a very low difference in spectral indices was noticed at the first plant stages, but the differences began to appear after 97 days from sowing, because of the addition of irrigation during tillering stage. The results showed high significant correlation between the different indices and LAI and fresh weight, it was positive with EVI, at 0.05% level of significance. It was noticed that all three spectral indices had a relation with water content, but the dry weight showed a positive correlation but not significant. It has been found a high significant correlation between the indices and grain yield at each radiometric measurement except after 62 and 208 days after sowing, which are accompany with the first and last stages of growth plant, respectively. It is also noticed that NDVI, recorded the highest correlation values after 145 days from sowing, but the other indices mNDVI₇₀₅, mSR₇₀₅, NDVI₇₀₅, EVI, and SR recorded the highest correlation values after 165 days from sowing, which coincides with the maximum vegetation growth. With respect to yield prediction, it has been found that the best linear model was with the SRI index after 145 from sowing, besides the spectral indices SRI and mSR705 which also gave a good prediction linear model after 165 days from sowing.

Keys Words: Vegetation indices, Broad band, Narrow band, Yield Prediction, Wheat.

Full paper in Arabic: PDF