The aim of this study was to obtain spectral reflectance values by using
 remote sensing method in alfalfa plant and to estimate nitrogen levels by using
 these values. The treatments were carried out in both field and greenhouse
 conditions. Different nitrogen, phosphorus and potassium
 doses were applied to plots in the field and pots in greenhouse. Spectral
 reflectance measurements were made at both the canopy (general) level and the
 single leaf level when the plants were in pre-flowering stage. Reflectance measurements were undertaken using a portable
 spectroradiometer measuring the wavelength range of 325-1075 nm of the
 electromagnetic spectrum. Plant probe with artificial light source and leaf
 clip were used for leaf measurements. Statistical analyses were conducted using
 stepwise regression analysis
 implemented in MINITAB-13 statistical program. As a result of the study,
 significant relationships (Field-canopy: 0.94, Field-leaf: 0.23,
 Greenhouse-canopy: 0.55, Greenhouse-leaf: 0.92) were determined between
 the nitrogen levels in the plant and the reflectance values. Also results showed that
 changes in nitrogen levels affect reflectance in the visible region (400-700
 nm) of the spectrum. When the wavelengths were evaluated separately, it was observed
 that the wavelengths of the blue, red and near infrared regions, which are
 important for photosynthesis, can be used to estimate the nitrogen levels.