The potential of L. scoparium, K. robusta and P. radiata to mitigate N-losses in silvopastural systems

Silvopastoral systems aim to enhance economic, cultural and social principles by sustainably combining forest management with agriculture. In these typically high-nitrogen (N) environments, plant species selection can profoundly influence N fluxes. For grazed pastures, plants may be exposed to urine patches that have received the equivalent of up to 1000 kg N ha(-1). We aimed to determine the growth and N fluxes in three potential trees that may be used in silvopastoral systems: L. scoparium, K. robusta and P. radiata. Plants were grown in a greenhouse lysimeter experiment, with controlled. irrigation and temperature and exposed to N at rates of 200 kg ha(-1) equiv. for 15 weeks, followed by the addition of 800 kg ha(-1) N equiv, to simulate a urine patch. Urea produced a positive growth response of all plant species. Treatments containing L. scoparium and K. robusta leached lower amounts of nitrate (NO3-) (2 kg ha(-1) NO3-) compared to P. radiata (53 kg ha(-1)). Measurements of N2O over 20 days after the application of 800 kg N ha(-1) indicated an inhibitory effect of L scoparium and K. robusta on denitrification, hence loss of N via N2O. Both L scoparium and K. robusta demonstrated that they have potential to reduce N-losses in silvopastural systems, while producing valuable biomass.