Evaluating Sunn Hemp Intercropped in Tall Fescue Pastures for Summer Stocker Cattle Using Proximal and Satellite Sensing

ABSTRACT Tall fescue (TF, Lolium arundinaceum (Schreb.) Darbysh.) pasture productivity declines substantially during summer months due to elevated temperatures and reduced precipitation, presenting significant challenges to forage‐based livestock systems. This study evaluated whether strategically timed nitrogen (TF+N, (TF, Lolium arundinaceum (Schreb.) Darbysh cv. BarOptima Plus E34) application or intercropping with the warm‐season legume sunn hemp (SH, Crotalaria juncea (Linnaeus.); TF+SH) could enhance summer herbage accumulation, nutritive value, and cattle performance in TF pastures. Ground‐based ultrasonic canopy sensors and satellite‐derived vegetation indices (PlanetScope imagery) were integrated with machine learning models to predict biomass dynamics throughout the grazing season. Tall fescue fertilised with nitrogen significantly improved crude protein (CP) concentrations (12%–13% TF−N vs. 16%–17% TF+N; p < 0.001) and increased total seasonal forage yields, raising carrying capacity by approximately 29% ( p = 0.0038) and body weight gain by 36% ( p = 0.0128) compared to unfertilised controls. Sunn hemp improved late‐summer forage quality with the greatest in vitro true digestibility during August and September ( p < 0.0001) but did not increase cattle gains due to its short grazing window. Overall, strategic nitrogen application remains the most effective practice for sustaining TF productivity in stocker systems. However, sunn hemp intercropping provides a partial substitute to synthetic nitrogen inputs that may fit specific animal marketing strategies.