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In rotational grazing systems, it is common practice to apply nitrogen (N) fertiliser within 24 h of grazing thus resulting in addition of N fertiliser to urine patches. However, there is a lack of information on what the potential is, if any, to use this common practice to deliver N stabilisers to urine patches via N fertiliser formulations to reduce N losses to the environment. The objective of this study was to investigate the effect of applying urea fertiliser (with and without N stabilisers) 24 h after urine patch deposition on NH emissions. Treatments included (1) urine, (2) urea, (3) urine + urea, (4) urine + urea with N-(butyl)thiophosphoric triamide (NBPT), (5) urine + urea with dicyandiamide (DCD) and (6) urine + urea with both NBPT and DCD. Treatments were applied on two occasions, May and June, under contrasting soil moisture and meteorological conditions to a temperate grassland site. Urine (569-883 kg N ha) was applied 24 h prior to urea fertiliser application (40 kg N ha). There was no significant reduction or increase in NH emission factors from treatments receiving the two N stabilisers (NBPT and DCD) in the May and June application timings compared to the other treatments. The results of this study suggest that common farm practice of applying N fertiliser the day after grazing in rotational grazing systems offers no reduction in NH emission rates from urine patches where the N stabiliser inclusion rate is designed to reduce the fertiliser-based N losses only. [ABSTRACT FROM AUTHOR]

Deposition of urine and dung in pasture-based livestock production systems is a major source of ammonia ( NH3) volatilization, contributing to the eutrophication and acidification of water bodies and to indirect nitrous oxide emissions. The objectives of this study were to (i) measure NH3 volatilization from dung and urine in three seasons, (ii) test the effect of spiking urine with the nitrification inhibitor dicyandiamide ( DCD) on NH3 volatilization and (iii) generate NH3 emission factors ( EFs) for dung, urine and urine + DCD in temperate maritime grassland. Accordingly, simulated dung, urine and urine spiked with DCD (at 30 kg DCD/ha equivalent rate) patches were applied to temperate grassland. Treatments were applied three times in 2014 with one measurement of NH3 loss being completed in spring, summer and autumn. The NH3-N EF was highest in spring, which was most likely due to the near absence of rainfall throughout the duration of loss measurement. The EFs across the experiments ranged between 2.8 and 5.3% (mean 3.9%) for dung, 8.7 and 14.9% (mean 11.2%) for urine and 9.5 and 19.5% (mean 12.9%) for urine + DCD, showing that ammonia loss from dung was significantly lower than from urine. Aggregating country-specific emission data such as those from the current experiment with data from climatically similar regions (perhaps in a weighted manner which accounts for the relative abundance of certain environmental conditions) along with modelling is a potentially resource-efficient approach for refining national ammonia inventories. [ABSTRACT FROM AUTHOR]

Aims: The objectives of this study were to compare techniques for measuring biological nitrogen fixation (BNF) and to assess how fertiliser N input affects the balance between BNF and sustainable herbage production on perennial ryegrass ( Lolium perenne L.)/white clover ( Trifolium repens L.) grassland. Methods: Biological N fixation and herbage production by white clover based grassland was measured in 2011 and 2012 under four nominal annual fertiliser N inputs: 0 (0N), 86 (86N), 140 (140N) and 280 kg ha (280N). Biological N fixation was measured using the N isotope dilution and N natural abundance techniques under all fertiliser N inputs and also using the nitrogen difference technique under 0N. Results: The two N techniques produced similar annual estimates of above-ground BNF across the range of fertiliser N inputs. Fertiliser N input resulted in higher herbage dry matter yield, but reduced annual BNF which averaged 80, 64, 66 and 47 kg ha on 0N, 86N, 140N and 280N, respectively, across both techniques and years. Conclusions: The two N techniques were comparable in estimating BNF. Intermediate fertiliser N inputs achieved a balance between minimising detrimental impact on BNF and potential N loss while producing more herbage DM yield than clover swards receiving no fertiliser N. [ABSTRACT FROM AUTHOR]

This study investigated changes in soil organic carbon ( SOC) in a poorly drained clay loam soil under (i) permanent grassland ( PG) over 7 years and (ii) after PG renovation over 2·5 years. The experimental area was divided into four blocks with four paddocks per block. Composite soil samples from each PG block were taken to 30-cm depth on five occasions between 2004 and 2011. In June 2008, one paddock per block was renovated by ploughing and reseeding and sampled as above on the latter four occasions. Renovation decreased SOC ( P < 0·05) by 32·2 t ha−1 in the 2·5 years following ploughing; the difference developed almost entirely (86%) in the first four months. Renovation had no effect on above-ground productivity, standing root and stubble phytomass or on dissolved organic matter leaching. Therefore, soil respiration was considered to be a single potential pathway responsible for the SOC loss from renovated grassland. Although a simple linear regression indicated a tendency for PG to accumulate SOC, there was no evidence of recovery in SOC to previous levels following renovation during the study period. These results could have implications for greenhouse gas inventories in countries where PG is an important land-use type. [ABSTRACT FROM AUTHOR]