The effect of establishment method and shade zone within solar arrays on pasture production in an agrivoltaic production system

Animal grazing to control understory herbage growth in photovoltaics sites presents a substantial opportunity for animal and energy production within the same site. However, there is a paucity of information on the effect of field preparation method within solar arrays on the establishment and productivity of pastures. Thus, the current study investigated the effects of field preparation and shade within solar arrays on plant germination and subsequent herbage yield in an agrivoltaic system. The treatments were (i) tillage and plastic cover (TP), (ii) plastic cover only (P), and (iii) herbicide application prior to sowing (H). A diverse pasture mixture, comprised of perennial ryegrass (Lolium perenne L.), orchardgrass (Dactylis glomerata L.), white clover (Trifolium repens L.), birdsfoot trefoil (Lotus corniculatus L.), chicory (Cichorium intybus L.), and plantain (Plantago lanceolata L.) was direct drilled within solar arrays in spring 2020. The experiment layout was a completely randomized plot design with three replicates. The pastures were harvested in fully shaded, partially shaded and non-shaded zones within solar arrays in each plot in July and October 2020. The average across the treatments herbage dry matter (DM) yield was 1127 kg DM ha⁻¹ and 1305 kg DM ha⁻¹ in July and October 2020, respectively. While the effect of establishment method was significant with plastic cover and tillage application resulting in the highest DM yield of 1547 kg DM ha⁻¹, the herbage yield in three shade zones within the solar arrays did not differ in July 2020. The herbicide application alone had the lowest DM yield at the establishment stage in summer. The effect of establishment method on forage DM yield was not significant in October 2020. However, a treatment×shade zone interaction was detected as the non-shaded, middle zone in herbicide only treatment had substantially lower DM yield than other two shade zones.