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

• Published in: Environmental pollution (1987) 2017-06, Vol.225, p.12-19
• Main Authors: Esperschuetz, J., Balaine, N., Clough, T., Bulman, S., Dickinson, N.M., Horswell, J., Robinson, B.H.
• Format: Article
• Language: English
• Subjects: Agriculture - methods; Denitrification; Fertilizers - analysis; Forestry - methods; Forests; Kānuka; Leaching; Mānuka; Nitrates; Nitrogen - analysis; Nitrous oxide; Pine; Trees; Urea
• ISSN: 0269-7491; 1873-6424
• DOI: 10.1016/j.envpol.2017.03.042

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. [Display omitted] •Tree species selection in silvopastoral systems can minimize N losses.•Mānuka, kānuka and pine respond positively to agricultural rates of N addition.•Mānuka and kānuka reduce nitrate leaching after urea application compared to pine.•Both mānuka and kānuka inhibit denitrification. L. scoparium and K. robusta minimize N losses from leaching and N2O emissions after urea application.