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

Abstract

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 (N 2 O) 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 ( ) leaching and N 2 O losses were measured in a lysimeter experiment. Catalpol, but not aucubin, was exudated by plantain roots. N 2 O emissions were decreased by plantain swards and by ryegrass‐white clover swards to which aucubin was also applied. Aucubin had no effect on leaching. Urine from cows grazing plantain had no effect on N 2 O 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 N 2 O emissions via mechanisms in the soil separate from the decreased emissions resulting from the lower N concentration of urine derived from cows grazing plantain.