A preliminary investigation of the effect of solar panels and rotation frequency on the grazing behavior of sheep (Ovis aries) grazing dormant pasture

Summary

Vegetation management on solar farms can be accomplished through targeted grazing with sheep. To the authors’ knowledge, no research has been conducted to date on sheep grazing behavior on solar farms, yet such research is crucial to inform grazing management practices for contract grazers on solar farms. The objectives of this study were to investigate both the effects of solar panels on sheep grazing behavior and the grazing management strategy (intensive rotational grazing (1-day rotations (1d))) or rotational grazing (4-day rotations (4d))) best suited for vegetation management on a solar farm. Data were collected on Gold Tree Solar Farm in San Luis Obispo, CA, USA. Sheep with predominantly Dorper genetics (over 99%; n = 80) were stratified by body weight (BW) and age in a crossover design across treatment grazing locations, solar farm (S) or native rangeland (NR), and grazing managements, intensive rotational (1d) or rotational (4d). Grazing location treatments (S or NR) were randomly assigned a grazing management, 4d (paddock size = 0.405 ha, 4 days/paddock), or 1d (paddock size = 0.101 ha, 1 day/paddock, 4 paddocks), resulting in a 2 × 2 factorial design. All sheep were equipped with a HOBO Pendant G data logger (Onset Computer Corporation, Bourne, MA, USA) in a medial-dorsal position on their necks using vet wrap (Dura-Tech), to record ‘grazing’ behavior, defined as standing or walking slowly with the head down. The sensitivity, accuracy, and precision were > 90% for ‘grazing’ behavior with 2-minute intervals. ‘Grazing’ behavior exhibited a treatment × management (< 0.01) interaction. Both solar (S-4d and S-1d) groups spent more time (< 0.01) ‘grazing’ than both NR (NR-4d and NR-1d) groups. The presence of solar panels may have provided sheep relief from heat, wind, and rain, which could increase grazing activity. During the study, forage was senescent and low-quality in terms of nutritive value. Both forage digestibility and protein content were higher in the S than in the NR paddocks. Sheep spent less time ‘grazing’ under intensive rotational management (1d) when compared with rotational management (4d) (< 0.001). The use of sheep for vegetation management on solar farms has great potential. Sheep are effective grazers, easily able to maneuver between solar panels and can graze on steep slopes utilizing the panels to provide shade and protection from climatic conditions. In conclusion, utilizing a mix of intensive rotational and rotational grazing according to forage conditions – rotational 4d grazing management types being most effective for grazing behavior with senescent forage conditions – may be the most effective grazing management strategy on solar farms.