Fertiliser and seasonal urine effects on N₂O emissions from the urine-fertiliser interface of a grazed pasture

Abstract

Significant areas of ruminant-grazed pastures are simultaneously covered by excreted urine and fertiliser nitrogen (N). However, the effect of overlapping N inputs on nitrous oxide (N 2 O) emission factors has not been studied. Three rates of 15 N-labelled urea fertiliser were applied with either no urine, an autumn-urine or a spring-urine application. These treatments were applied to perennial ryegrass pasture (Lolium perenne L.) and N 2 O fluxes were determined over 373 days using standard static closed chamber techniques. Cumulative N 2 ON fluxes ranged from 766 to 4332 g N 2 ON ha-1 (0.36%-0.74% of total N applied) and were lowest in the absence of urine; however, no fertiliser rate effect occurred regardless of urine presence or season of application. Urine-elevated N 2 ON fluxes followed urine applications for up to 40 days, resulting in lower fertiliser contributions to the N 2 ON fluxes at these times. Total 15 N recoveries as N 2 ON were ≤0.04% and did not differ with fertiliser rate.

Sources and priming of nitrous oxide production across a range of moisture contents in a soil with high organic matter

“…Similar to our study, Müller, Laughlin, Spott, and Rütting (2014) found that more than half of the total N 2 O came from the SOM, according to experimental and modeling work in an old grassland soil enriched with organic C (i.e., 66 g C kg −1 ) (Figure 3). This is also in line with Buckthought, Clough, Cameron, Di, and Shepherd (2015), who studied a grazed pasture with a high soil organic C (i.e., 55 g C kg −1 ), that had received double the urea addition rate of our study, in which the SOM contribution still made up the majority of the N 2 O produced. As for our soil, it is reasonable to assume that a major contribution of SOM mineralization to both the total and the primed N 2 O can emerge only when an abundant SOM substrate exists.…”

“…For Buckthought et al. (2015), we only included their 200 kg urea‐N ha −1 rate because this N rate is closer to that in our study. The other two studies used ammonium nitrate at 180 kg N ha −1…”

Fourfold Increase in Pumpkin Yield in Response to Low-Dosage Root Zone Application of Urine-Enhanced Biochar to a Fertile Tropical Soil

“…Field applications of nutrient-enhanced biochars can potentially reduce the necessity to apply mineral fertilizers, can benefit organic farmers, or farmers from low-income regions, and can improve biochar related cost-benefit ratios. Moreover, it is very likely that combining urine and biochar would reduce adverse excess nutrient effects of sole urine applications, such as nitrogen leaching or N2O greenhouse gas emissions [31].…”

Nitrogen fertiliser interactions with urine deposit affect nitrous oxide emissions from grazed grasslands

“…By contrast, Buckthought et al (2015b) found no significant difference between urine applied alone and combined to N fertiliser (urea) with an application at high soil moisture content due to the soil being wetted with 800 mm of water before application of the treatment.…”

“…Due to the use of control plots in these studies including the current study, and the subtraction of 'background' emissions from the treated plots, the reported EFs are unlikely to vary from those calculated from annual studies. For most reported results, the vast majority of annual N 2 O emissions are emitted within 40 days after application (Buckthought et al, 2015b;Cowan et al, 2019;Skiba et al, 2013). In this study, small fluxes near the natural variability in emissions from the control treatment (after 40 days) were not considered.…”