Remote sensing techniques to assess the weeds adaptability to salinity stress induced by soil changes

Weeds pose one of the major threats to plant production, as they can reduce yield, interfere with harvest, and host different harmful organisms. Unlike crops, weeds are characterized by great plasticity and adaptability to agroecosystem changes, making them an even more critical threat in a constantly changing environment. The influence of climate change in the form of different stresses to which plants are being more and more exposed is being extensively studied in crops, yet there are few studies concerning weeds. Still, considering the adaptability potential of weeds, they can represent an even more significant threat to agricultural production when abiotic stress, such as salinity, is introduced in the agroecosystem. Currently, remote sensing techniques may be exploited to derive useful, frequent, and low-cost information at different spatial scales. In this work, the Structure from motion (SfM) technique paired with Unmanned Aerial Vehicles (UAV) was used to map the distribution changes of Abutilon theophrasti in July and August 2022 in three different crop fields in the Po river delta, North-Eastern Italy. The multi-temporal orthomosaics obtained by two various SfM surveys had an image resolution of 2 cm, allowing an accurate photo interpretation and the realization of precise maps of species distribution. In the meantime, different soil samples have been taken from the fields above, and their position was measured by a Global Navigation Satellite System (GNSS), GeoMax Zenith 40. The salinity level of soil samples has been determined by measuring the electrical conductivity using XS Instruments COND 80 electrical conductivity meter (Giorgio Bormac s.r.l, Carpi, Italy) at a sensitivity of 1 µS. Salinity values were spatialized in the study areas, realizing salinity maps through the spatial interpolation tools of the Geographic information system (GIS) software. The salinity maps overlapped the maps of single plants of A. theophrasti. In both of the multi-temporal surveys performed, results show that plants of A. theophrasti can be found in areas where the soil salinity is higher than 8 dS/m, where most of the crop plants have perished.  Considering that the weed plants were present at the same place in both surveys, this indicates that A. theophrasti can tolerate the rise of salinity in the fields better than the crop plants and can therefore outcompete them. These results suggest that soil salinization can have a double negative effect on crop production, both causing abiotic stress and increasing competition.

Acknowledgments: This study was carried out within the Agritech National Research Center and received funding from the European Union Next-GenerationEU (PIANO NAZIONALE DI RIPRESA E RESILIENZA (PNRR) – MISSIONE 4 COMPONENTE 2, INVESTIMENTO 1.4 – D.D. 1032 17/06/2022, CN00000022).