Estimation of Nitrogen Levels By Remote Sensing Method in Alfalfa (Medicago sativa L.)

Özet

The aim of this study was to obtain spectral reflectance values by usingremote sensing method in alfalfa plant and to estimate nitrogen levelsby using these values. The treatments were carried out in both field andgreenhouse conditions. Different nitrogen, phosphorus and potassiumdoses were applied to plots in the field and pots in greenhouse. Spectralreflectance measurements were made at both the canopy (general) leveland the single leaf level when the plants were in pre-flowering stage.Reflectance measurements were undertaken using a portablespectroradiometer measuring the wavelength range of 325-1075 nm ofthe electromagnetic spectrum. Plant probe with artificial light sourceand leaf clip were used for leaf measurements. Statistical analyses wereconducted using stepwise regression analysis implemented inMINITAB-13 statistical program. As a result of the study, significantrelationships (Field-canopy: 0.94, Field-leaf: 0.23, Greenhouse-canopy:0.55, Greenhouse-leaf: 0.92) were determined between the nitrogenlevels in the plant and the reflectance values. Also results showed thatchanges in nitrogen levels affect reflectance in the visible region (400-700 nm) of the spectrum. When the wavelengths were evaluatedseparately, it was observed that the wavelengths of the blue, red andnear infrared regions, which are important for photosynthesis, can beused to estimate the nitrogen levels.