The role of an Ascophyllum nodosum extract in lowering the environmental impact and improving nitrogen use efficiency in pasture systems under a reduced nitrogen regime

Abstract Nitrogen is a macronutrient that is applied in substantial amounts as a chemical fertiliser to conventional agricultural systems. However, loss of nitrogen from agricultural systems to the environment, in the form of gases (N 2 O) and leachate (NO 3 ), is detrimental to the environment. As such, improving the nitrogen use efficiency (NUE) of crops is an essential component of sustainable agriculture. Biostimulants are a category of products that improve NUE when applied to crops and/or soil. Here, we examined the effects of PSI-362, an Ascophyllum nodosum biostimulant mixed with and applied on calcium ammonium nitrate (CAN) granules, on grass yield, quality traits, and environmental impacts in lysimeter trials under natural weather conditions. By using PSI-362, it was possible to reduce nitrogen application by 25% without a significant loss in yield compared to a conventional 100% N system. We also observed an increase in NUE under a 75% N with PSI-362 co-application fertilisation regime, and a significant increase in crude protein content compared to the 100% N fertilisation controls. Furthermore, this reduced nitrogen application also resulted in reduced nitrogen loss through leachate (NO 3 ) and N 2 O to the atmosphere. The total NUE for PSI-362 + fertiliser granules ranged from 58.7% to 78.6% depending on the biostimulant dose, which was significantly better than the fertiliser alone. Our results showed that this biostimulant, which can easily be incorporated into conventional agronomic practices, allows for a more sustainable approach to pasture-based systems.