Schmidhalter (2024) 15N mass balance technique for measuring ammonia losses from soil surface-applied slurries containing various additives. Journal of Plant Nutrition and Soil Science. DOI: 10.1002/jpln.202400235

Anthropogenic ammonia emissions, primarily from agriculture, contribute significantly to air pollution, soil acidification, and water eutrophication. These emissions, mostly from livestock and biogas slurry, need effective mitigation to protect human health and ecosystems. Traditional slurry treatments often overlook the potential of additives to reduce these emissions. In this context, a new study led by Urs Schmidhalter from the Technical University of Munich presents a novel 15N mass balance technique to measure ammonia losses from soil surface-applied slurries containing various additives.

The study experimented with 18 different additives, including inorganic and organic adsorbents, sulfuric acid, molasses with and without effective microorganisms, and water dilutions. These were applied to soil-filled containers under outdoor conditions to measure their effectiveness in reducing ammonia emissions. The results showed that adsorbents had minimal impact on ammonia reduction. However, acidification with sulfuric acid significantly reduced emissions, especially at lower pHpH is a measure of how acidic or alkaline a substance is. A pH of 7 is neutral, while lower pH values indicate acidity and higher values indicate alkalinity. Biochars are normally alkaline and can influence soil pH, often increasing it, which can be beneficial More levels. Molasses, both alone and with microorganisms, also effectively reduced ammonia losses, though adding microorganisms provided no additional benefit. Water dilution reduced emissions significantly, though this method increases the volume of slurry that needs to be managed.

The 15N mass balance technique demonstrated high precision in quantifying ammonia losses, suggesting it as a reliable method for evaluating the effectiveness of different additives. This method could serve as a standard for future studies and practical applications in reducing agricultural ammonia emissions. The study highlights the importance of testing locally available additives to find practical and effective solutions for farmers.