Nitrogen-Enriched Organic fertilizer (NEO) elevates nitrification rates shortly after application but has no lasting effect on nitrification in agricultural soils

Abstract

In times of growing population, scarcity of arable land, and increasing use of synthetic nitrogen, new sustainable fertilizers are needed to enhance the resilience of global agri-food systems. Nitrogen-Enriched Organic fertilizer (NEO) is an example of a potentially sustainable fertilizer. Dinitrogen (N2) is captured from the air by a plasma process and mixed as nitrate (NO3−) and nitrite (NO2−) with animal slurries or other liquid organic fertilizers. This process strongly acidifies the slurry, which, together with the resulting high NO2− content, may result in toxic inorganic or organic N compounds. Here we test the effect of NEO produced from cattle slurry and biogas digestate on soil nitrification, i.e., the conversion of NH4+ to NO2− and NO3− mediated by aerobic autotrophic bacteria and archaea. We compared potential nitrification rates by laboratory incubation in soil samples from two trials (cereal and grass) fertilized with NEO and other fertilizers for two consecutive years. We also studied the immediate nitrification response to NEO in 73-hour bottle incubations. In agitated soil slurries, NEO strongly stimulated nitrification rates irrespective of feedstock (more than 2-fold), exceeding rates in ammonium controls. In loosely placed soil, a similar pattern was found, but this time ammonium chloride also resulted in high nitrification rates. By contrast, differences in nitrification rates between field-fertilized soil samples were minimal and negligible. Therefore, we conclude that despite the intense stimulation of nitrification by NEO right after application to soil, NEO has no long-lasting effects on nitrification under field conditions. This implies that NEO does not impose adverse effects on soil nitrifier communities.

Nitrous oxide and methane fluxes from plasma-treated pig slurry applied to winter wheat

“…We found that the plasma induction process increased the nitrate-N content of the pig slurry; the higher content of inorganic N combined with the C in the pig slurry is likely to be responsible for the higher N 2 O emissions (Shurpali et al 2016;Li et al 2022) from TPS compared to PS. Mousavi et al (2023) found that the nitrification potential of plasma-treated pig slurry was higher than that of other fertilisers due to its higher volatile organic C content, which reduces ammonia immobilisation, and so may also explain the higher N 2 O emissions from TPS. Denitrification is highly influenced by pH, with denitrification being slowed or even inhibited at lower pH levels (Liu et al 2010;Olaya-Abril et al 2021).…”

Plasma Treated Cattle Slurry Moderately Increases Cereal Yields

“…This difference in nitrogen absorption timing may help explain why MiNEO120 consistently resulted in higher wheat yields than barley in most of our trials. Another contributing factor could be the high nitrification potential of NEO, which leads to greater availability of plant-accessible nitrate over a concentrated period of 3-4 days following application [18]. This rapid release of nitrate may particularly benefit wheat [31,32].…”

“…Since NEO is a novel product, assessing its impact on plant yield and its effectiveness compared to conventional fertilizers, e.g., mineral fertilizers, cattle slurry, etc., is essential before considering its commercialization. Thus, to accomplish this, we at Inland Norway University of Applied Sciences (INN) conducted comprehensive trials to document and compare the effects of NEO on soil health [17,18] and plant yields in the growing chamber [19] and cereal and grass fields at different locations in Norway over three years (2020 to 2022).…”