Biomass Estimation of Sporobolus spartinus with Multispectral Images from a Fixed-Wing Unmanned Aerial Vehicle and a Spectrometer

Sporobolus spartinus (Trin.) P.M. Peterson & Saarela (=Spartina argentinensis Parodi, common name: espartillo) is a perennial C4 grass that dominates in many communities from a region named "Bajos Submeridionales" in the northern part of Santa Fe province. It produces high quantity of biomass but, due to its low digestibility, cattle risers often burn it in order to stimulate the growth of more tender leaves. This burnt biomass could be used in order to produce bioenergy, thus knowing its availability is mandatory in order to select areas with higher biomass. In this research, S. spartinus biomass reflectance from a farm near the town of Galvez was measured with i: a multispectral camera mounted in a Drone and ii: a hyperspectral camera in a spectrometer in two different dates, one in October of 2019 and the other in March of 2020. S. spartinus biomass presented higher total biomass (average of 7700 kg of dry matter per hectare) in October and most of it (67%) was senescent biomass while in March, total biomass accounted for 5300 kg per hectare and only 38% of it was standing dead biomass. A Normalized index was able to explain 33% of total biomass variability with both instruments. Due to the fact that either green or senescent biomass can be used for bioenergy, our aim was to estimate those using remotely sensed multispectral images.