The effect of dicyandiamide addition to cattle slurry on soil gross nitrogen transformations at a grassland site in Northern Ireland

Abstract

Many studies have shown the efficacy of the nitrification inhibitor dicyandiamide (DCD) in reducing nitrous oxide (N 2 O) emissions and nitrate (NO 3 − ) leaching. However, there is no information on the effect of DCD on gross soil N transformations under field conditions, which is key information if it is to be used as a mitigation strategy to reduce N losses. The current field study was conducted to determine the effect of DCD on ten gross nitrogen (N) transformations in soil following cattle slurry (CS) application to grassland in Northern Ireland on three occasions (respectively. The lower inhibition level in October 2010 was thought to be due to the higher rainfall and soil moisture content in that month compared to the other application times. As DCD strongly inhibited NH 4 + oxidation following CS application, it also decreased the rate of total NO 3 − consumption, since less NO 3 − was formed. The rates of mineralization from recalcitrant organic-N (M Nrec ) were higher than from labile organic-N (M Nlab ) on all occasions. The DCD significantly increased total mineralization (M Nrec + M Nlab ) following CS application in June 2010 and March 2011, but had no significant effect in October 2010. In contrast, the rate of immobilization of labile organic-N (I NH4_Nlab ) was higher than from recalcitrant organic-N (I NH4_Nrec ) on all occasions, accounting for 0·878-0·976 of total NH 4 + immobilization from CS. The DCD significantly increased total immobilization (I NH4_Nrec + I NH4_Nlab ) when CS was applied in June 2010, but had no significant effect at other times of the year.Dicyandiamide was shown to be a highly effective inhibitor of ammonium oxidation at this grassland site. Although there was evidence that it increased both NH 4 + mineralization and immobilization following CS application, its effect on these processes was inconsistent. Further work is required to understand the reason for these inconsistent effects: future improvements in 15 N tracer models may help.

Ammonia emissions from urea, stabilized urea and calcium ammonium nitrate: insights into loss abatement in temperate grassland

“…In a field study at HB, McGeough et al . () observed significant but inconsistent effects of DCD on MIT including net immobilization of N. Furthermore, Ernfors et al . () in a laboratory study with slurry found that the effects of DCD on MIT varied between soils.…”

Nitrogen use efficiency and nitrous oxide emissions from five UK fertilised grasslands

“…More information related to these experiments is found in www.ghgplatform.org.uk. Archived data sources are: Bell et al (2017); Cardenas et al (2017); McGeough et al (2017); Thorman et al, 2017a, Thorman et al, 2017b.…”

Soil recalcitrant but not labile organic nitrogen mineralization contributes to microbial nitrogen immobilization and plant nitrogen uptake

“…However, M Nrec was the main N mineralization process in grassland (McGeough et al, 2014) and paddy soil (Chen, Zhang, et al, 2016).…”

“…(2016) also found that M Nlab was 2.5 times higher than M Nrec in subtropical forests. However, M Nrec was the main N mineralization process in grassland (McGeough et al., 2014) and paddy soil (Chen, Zhang, et al., 2016). Previous investigators reported that POM is typically considered a more temperature‐sensitive indicator (Benbi et al., 2014; Georgiou et al., 2024), but such studies do not consider the rhizosphere.…”