NORMALIZED DIFFERENCE VEGETATION INDEX (NDVI) IN THE EVALUATION OF PHENOLOGICAL DYNAMICS IN DACTYLIS GLOMERATA L. AND MEDICAGO SATIVA L

Abstract

The fodder species Medicago sativa L. and Dactylis glomerata L. are appreciated for their yield, due to their high perenniality and the large number of scythes in a year, as well as for their different use. In recent years, fodder crops and grasslands have been given a special place in precision agriculture, and by using remote sensing and implicitly the Normalized Difference Vegetation Index (NDVI), the vegetation status of crops is appreciated. In this context, the paper aims to capture the time dynamics, in different phenological stages, of the species Dactylis glomerata L. and Medicago sativa L., based on spectral information extracted from the analysis of PlanetScope satellite images, with a spatial resolution of 3 m. carried out in the experimental lots of the Lovrin Agricultural Research and Development Station - taking into account two plots cultivated with Dactylis glomerata L. (1.22 ha) and Medicago sativa L. (0.8 ha), located in the second and third year of vegetation. The analysis of the spectral information, materialized by NDVI values, with the data collected in the field regarding the dynamics of crop development (BBCH Code) led to the extraction of some useful conclusions for the agricultural practice regarding the health status of the two crops. NDVI values in Dactylis glomerata L. and Medicago sativa L. were different depending on crop evolution. Thus, at the end of winter, the NDVI index had the same average values for both crops (0.746), validated by field observations on crop health. Later on, for the Medicago sativa L. crop, the values of the NDVI index are increasing until sprout phenophase, when green mass was mowed for fodder. In the seed culture of Dactylis glomerata L. the values of the NDVI index are also increasing in the vegetative phase and reach the maximum threshold of 0.833, on 12.05.2020, in the phenophase - 50% of flowering (BBCH), after which it there is a decrease in them alonside with the change of the color of the plants as a result of the appearance of spikelets and later their ripening. The values of the NDVI index immediately after harvest in the two crops are different, being determined by their biological peculiarities.