Impact of ribwort plantain (Plantago lanceolata L.) and mixtures with red clover (Trifolium pratense L.) as a precrop of winter wheat (Triticum aestivum L.) on nitrous oxide and methane emissions

Summary

In crop rotations, ley termination can result in nitrogen losses. To preserve this nitrogen, ribwort plantain (Plantago lanceolata L.) may serve as a biological nitrification inhibitor. In a two-year field study in Central Europe, the potential of ribwort plantain as a substitute for Italian ryegrass (Lolium multiflorum L.) in mixtures with red clover (Trifolium pratense L.) was evaluated as a precrop for winter wheat. Sward mixtures included monocropped plantain, ryegrass and clover and 50/50 mixtures of clover with either plantain or ryegrass. After autumn ley termination, winter wheat was grown without additional fertilisation. The impact of precrop sward mixtures was evaluated for soil-derived emissions of nitrous oxide and methane, ecosystem respiration and nitrogen uptake of winter wheat. Only nitrous oxide background fluxes with cumulative emissions ranging from 0.08 to 0.99 kg nitrogen per hectare during the winter wheat seasons were detected. The highest nitrous oxide emissions occurred after monocropped red clover, and the lowest emissions occurred after monocropped plantain and ryegrass with both 50/50 mixtures in between. Ecosystem respiration (2nd year) and nitrogen uptake of winter wheat showed the same trend. Statistically significant differences confirmed that in the second year of the field experiment, the precrop of mixtured red clover and Italian ryegrass and sole cropped red clover lead to almost 4 times higher nitrous oxide-nitrogen cumulative fluxes compared to the precrop sole crop ribwort plantain. In the red clover crops stands, the nitrogen supply via symbiotic nitrogen fixation and the narrower carbon to nitrogen ratio in its plant residues compared to the plant residues of Italian ryegrass and ribwort plantain probably led to higher nitrate reserves in the soil and nitrous oxide emissions. As a result, it was not possible to quantify in detail under field trial conditions the contribution of the aucubin-induced nitrification inhibition of ribwort plantain to the lower nitrate stocks in the soil and nitrous oxide emissions that were found. In contrast, methane uptake was not influenced by precrop choice. Statistically, ribwort plantain had the same precrop effect on winter wheat as ryegrass in mixed swards with clover.