Spatial monitoring technologies for coupling the soil plant water animal nexus

Authors: Ashworth, Amanda; Kharel, Tulsi; Adams, Taylor; Sauer, Thomas; PHILIPP, DIRK - University Of Arkansas; THOMAS, ANDREW - University Of Missouri; Owens, Phillip

Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/14/2022
Publication Date: 3/3/2022
Citation: Ashworth, A.J., Kharel, T.P., Adams, T.C., Sauer, T.J., Philipp, D., Thomas, A., Owens, P.R. 2022. Spatial monitoring technologies for coupling the soil plant water animal nexus. Scientific Reports. 12. Article 3508. https://doi.org/10.1038/s41598-022-07366-2.
DOI: https://doi.org/10.1038/s41598-022-07366-2

Interpretive Summary: Agricultural systems are loosely defined as combining system components (soils, plants, and animals) and focuses on evaluating the interactions among these components, rather than the isolation of a single parameter. Against the backdrop of 60% increases in food production demands and the need for sustainable intensification, greater multi-disciplinary studies are needed to solve challenges facing agriculture. Further, silvopastures, or the combination of tree and animal production in one system is touted for its ability to minimize risk by allowing producers to respond to market fluctuations, while providing ecosystem services (such as greater shade for animals and greater soil carbon storage). However, it is largely unknown what drives grazing pressure in these systems. Therefore, researchers set out to conduct a systems-level study aimed at determining how soil characteristics are linked to plant production and ultimately animal response in a silvopasture. Researchers put global positioning system (GPS) tracking collars on cattle and and relationships with terrain, soil, and forage (two forage species; one native and one non-native) were explored. The study found that cattle preferred grazing the native grass-mix compared to the introduced forage, as well as preferred drier areas in the field (compared to wet areas). Greater grazing frequency also occurred on soils with greater nutrient levels and with forages with lower lignin, which corresponded to areas with lower elevation and greater tree size (increased shade). These results can be used to optimize grazing systems management, minimize producer risk, and help build our understanding of how systems function for sustainable intensification.

Technical Abstract: Systems-level studies aimed at determining how soil properties are linked to plant production and ultimately animal response spatially are lacking. This study aims to identify if grazing pressure is linked to soil properties, terrain attributes, and aboveground plant accumulation and nutritive value in a silvopastoral system. Orchardgrass (Dactylis glomerata L.; C3) and a big bluestem (Andropogon gerardii L.; C4) dominated native grass mix were seeded in alleys of five tree species during 2015 and replicated thrice. Poultry litter was annually applied to alleys at 84 kg N ha-1, with controls being represented by a 0 N rate. Summer grazing patterns of cattle were tracked from 2017-2019 using Global Positioning System collars on Angus-mix heifers (Bos taurus L.). Data were combined for fix (every 15 min) and tilt (head down greater than 70%). Weekly grazing hour per animal unit (hr ha-1 AU-1) was area weighted and relationships with terrain, soil, and forage parameters were explored from a 1-m digital elevation model. Over all summer grazing periods, cattle preferred grazing the native grass mix compared to orchardgrass (2.81 vs. 1.24 hr ha-1 AU-1) and udic (dry) landscape positions compared to aquic (wet) areas (2.07 vs 1.60 hr ha-1 AU-1). Greater grazing frequency occurred in udic soils with greater phosphorus and potassium contents and with accumulated forage with less lignin (P=0.05), which corresponded to reduced elevation and greater tree height and diameter (shade) during summer grazing. Combining spatial monitoring technologies (both soil and animal) with forage allowance can optimize grazing systems management spatially and temporally.