An interdisciplinary research team has made a significant discovery: willow leaves can drastically reduce ammonia (NH₃) and nitrous oxide (N₂O) emissions from cattle farming. This groundbreaking study, published in Agriculture, Ecosystems & Environment, suggests that a natural feed additive could make pasture farming more environmentally friendly, giving a new application to a traditional medicinal product.
Scientists from the Research Institute of Farm Animal Biology (FBN) in Dummerstorf, along with researchers from the Universities of Rostock, Munich, and Vienna, collaborated on this project. Their tests at FBN demonstrated that certain compounds in willow leaves can significantly cut environmentally and climate-damaging nitrogen emissions from cattle urine by up to 81%.
Nitrogen emissions pose a major challenge for global agriculture, contributing about 80% of ammonia and 81% of nitrous oxide emissions. Ammonia acidifies soils and over-fertilizes ecosystems, while nitrous oxide is a potent greenhouse gas, approximately 300 times more impactful than CO₂, persisting in the atmosphere for around 150 years. A significant portion of these emissions originates directly from ruminant urine on pastures, a source previously considered difficult to control with conventional methods.
“If we want to preserve pasture farming as an animal-friendly and sustainable form of livestock farming, we must also get a grip on its environmental impact,” stated PD Dr. Björn Kuhla, head of “Farming animals in sustainable resource cycles” at FBN.
Inspired by prior research on plant ingredients’ effects on metabolism, Kuhla and his team investigated whether salicin, a precursor to salicylic acid found in willow leaves, could influence nitrogen conversion in cattle. Their experiments revealed that feeding cattle salicylate-containing willow leaves dramatically reduced the formation of ammonia and nitrous oxide from urine excretions. Over 48 hours, they measured 14% less ammonia and an impressive 81% less nitrous oxide compared to a control group. The researchers believe these effects stem from both salicylic acid and other bioactive compounds in willow leaves.
Willows (genus Salix) are fast-growing woody plants traditionally used as medicinal and fodder plants in various parts of the world. In Germany, they’ve primarily served as energy crops or in agroforestry systems. Their newly discovered efficacy against nitrogen loss opens up new avenues for sustainable animal nutrition. “Willow foliage is a locally available, renewable raw material that is particularly suitable as a natural feed supplement for pasture farming—where other solutions fail,” Kuhla explained.
The next steps involve field trials to confirm these positive effects under real farming conditions, considering factors like feed intake, soil type, climate, and microbial activity. Scientists are also investigating potential effects on nitrate formation in the soil and exploring other deciduous species like poplar, which share similar properties with willows.
In the long term, researchers envision silvopastoral systems—combined pasture and wooded areas—where woody plants like willows could directly provide feed, improve the microclimate, and naturally reduce emissions. The use of willow leaf extracts as an additive in stable manure or slurry is also being explored, though further research is needed.
