Ammonia emissions and nitrogen use efficiency of untreated and plasma treated liquid organic materials

Abstract Manure management is a significant source of ammonia emissions in the EU. Ammonia emissions can damage sensitive habitats, pose a risk to human health and reduce crop available nitrogen supply from organic materials and manufactured fertilizers. Total ammoniacal‐nitrogen in liquid organic materials consists of both un‐ionized ammonia gas and ammonium in solution which are at an equilibrium that is pH and temperature dependant. At pH <6 the proportion of ammonia gas is very low, and acidification is recognized as a technique for reducing ammonia emissions from liquid organic materials. Air plasma treatment, which fixes nitrogen from air using a strong electric current, lowers the pH of liquid organic materials to around 5.5, from pH 7–8 for untreated materials. A series of seven replicated field experiments were used to compare the effects of plasma treated and untreated liquid organic materials on ammonia emissions, crop yield and nitrogen use efficiency following application to winter wheat. Results from the field experiments showed that ammonia emissions following the application of plasma treated liquid organic materials were 28%–83% lower than from the untreated materials and similar to emissions from mineral ammonium nitrate in the same experiments. The lower ammonia emissions increased the fertilizer value of the plasma treated liquid organic materials (compared with the untreated materials) by 45%. The increased crop available nitrogen supply from the plasma treated materials reduced the requirement for purchased nitrogen fertilizer applications to meet optimum crop demand.