Can secondary metabolites of plantain reduce N losses from urine patches?

ABSTRACT

Plantain (Plantago lanceolata L.) is a forage that produces secondary metabolites with one, aucubin, known to inhibit soil nitrification. This study aimed to quantify the exudation of aucubin and catalpol by plantain root systems in a hydroponic experiment; evaluate the effect of aucubin on nitrogen (N) leaching and nitrous oxide (N₂O) emissions from urine applied to plantain and ryegrass-white clover swards; and compare N losses from a ryegrass-white clover sward after urine from cows fed plantain and cows fed ryegrass-white clover was applied. Nitrate (${\mathrm{NO}}_3^{-}$) leaching and N₂O losses were measured in a lysimeter experiment. Catalpol, but not aucubin, was exudated by plantain roots. N₂O emissions were decreased by plantain swards and by ryegrass-white clover swards to which aucubin was also applied. Aucubin had no effect on ${\mathrm{NO}}_3^{-}$ leaching. Urine from cows grazing plantain had no effect on N₂O emissions, and N leaching when compared to the urine from cows grazing ryegrass-white clover with the same N content. We conclude the plantain sward and the aucubin applied to the ryegrass-white clover sward decreased N₂O emissions via mechanisms in the soil separate from the decreased emissions resulting from the lower N concentration of urine derived from cows grazing plantain.

KEYWORDS:

• Plantain
• secondary metabolites
• nitrous oxide
• nitrate leaching
• dairy systems

Acknowledgments

We are grateful to Massey University for providing analytical facilities. The authors thank Bob Toes, Micaela Reyes, Euan Nisbet and May Hedges for their technical support. The authors acknowledge Education New Zealand for the scholarship to the main author.

Disclosure statement

No potential conflict of interest was reported by the author(s).