Agrivoltaic arrays and effects of forage biomass and nutritive value of grasses and legumes for grazing dairy cattle

Forage crops for grazing dairy cattle grown underneath ground-mounted photovoltaic systems (PV) may provide a feed source for livestock production.The objective was to evaluate forage biomass and nutritive value of grasses and legumes grown under different PV conditions.Forages were planted underneath a 30-kW PV site (30kW), a 50-kW PV site (50kW) and one control pasture site without PV (CON) in 2022 and 2023 with 4 replicates per site.Solar sites were all located on the University of Minnesota West Central Research and Outreach Center grazing dairy farm and were not located next to each other but were 700m apart.Forage crops included alfalfa (Medicago sativa L.), field peas (Pisum sativum L.), meadow fescue (Schedonorus pratensis (Huds.)P. Beauv), orchardgrass (Dactylis glomerata L.), red clover (Trifolium pratense L.), brown midrib sorghum-sudan grass (Sorghum bicolor [L.] Moench ssp.Drummondii [Steud.]),white clover (Trifolium repens L.), and 3 grass and legume mixes with either alfalfa, red clover, or white clover.Forage samples were clipped (3 clippings per year) when forages reached approximately 25 to 35 cm in height, which corresponded to recommended pregrazing height for lactating dairy cows.Samples were analyzed for forage nutritive value.Forage biomass, dry matter and nutritive values were analyzed with PROC Mixed of SAS with the fixed effects of site (30kW, 50kW, or pasture), forage nested within site, year (2022 and 2023) and cutting (1,2 or 3) and the random effect of replicate nested within site.Forages produced less biomass at the 50kW (3,223 kg/ha) solar sites compared with 30kW solar site (8,968 kg/ha) and the control pasture (9,987 kg/ha).The 50kW forages had greater crude protein on a dry matter basis (23.8%) than the 30kW (20.1%) and control pasture (18.2%).The 50kW (54.4%) forages also had greater total-tract neutral detergent fiber digestibility than the 30kW (52.3%) and control pasture (49.1%).Forage biomass and nutrient nutritive values varied based on the solar array design and amount of sun exposure.