Can alternative forages substantially reduce N leaching? findings from a review and associated modelling

Nitrogen (N) leaching losses from grazed pasture systems pose a risk to the environment with mitigation strategies urgently required to achieve regulatory limits. There has been increased interest in alternative forages to manipulate excretion of urinary-N of livestock. This review summarises resear...

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Bibliographic Details
Published in:New Zealand journal of agricultural research 2020-01, Vol.63 (1), p.3-28
Main Authors: Bryant, Racheal H., Snow, Val O., Shorten, Paul R., Welten, Brendon G.
Format: Article
Language:English
Subjects:
APSIM
Computer simulation
Diuresis
Economics
Excretion
farm systems
Fertilizers
Leaching
Livestock
Lolium perenne
Metabolites
Microorganisms
Mitigation
modelling
Nitrate leaching
Nitrates
Nitrogen
Pasture
Plantago lanceolata
Profitability
Secondary metabolites
Soil dynamics
Urine
urine patch
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Summary:Nitrogen (N) leaching losses from grazed pasture systems pose a risk to the environment with mitigation strategies urgently required to achieve regulatory limits. There has been increased interest in alternative forages to manipulate excretion of urinary-N of livestock. This review summarises research on key forage attributes which affect the pattern of urine-N excretion. The literature showed an opportunity to alter both N concentration and moisture concentration of forages to reduce urine patch N loading. Complementary mitigations of extending the grazing rotation and reducing fertiliser were tested in simulations in addition to a diuresis effect on nitrate leaching in pastoral dairy systems. Findings suggested that forage species alone could not substantially reduce (by more than 20%) nitrate leaching. Combining all forage, management and systems-based solutions led to the greatest reductions in nitrate leaching, 59 and 31% for Waikato and Canterbury. Nonetheless, reductions in N loss came at the expense of pasture productivity which will likely affect profitability and farmer adoption of this suite of solutions in the absence of other drivers. The role of plant secondary metabolites in microbial dynamics has implications on N recycling in soil and rumen environments and this was identified as an area for further research.
ISSN:0028-8233
1175-8775
DOI:10.1080/00288233.2019.1680395