Helping farmers make better use of recyclable resources on farm

24 July 2019

Dairy farming systems in New Zealand have intensified over the past decade. This has increased the production of nutrient-rich dairy effluents, which are managed primarily through land application. This is cost-effective, as it avoids waste water treatment and/or landfill, and it also ensures that nutrients from effluent are recycled to grow pasture or crops. 

An important consideration in cropping situations relates to the pattern and magnitude of nitrogen supply from dairy effluents applied to cropping land. This is because sustainable economic and environmental outcomes are closely linked to maintaining a balance between soil nitrogen supply and crop nitrogen demand. 

The ability to predict effluent nitrogen supply would enable growers to make better use of dairy effluent as a resource to grow crops. 

This study looked at whether a measurable effluent attribute, or combination of attributes, could be used to predict nitrogen supply from dairy effluents applied to different soils. 

The study found that nitrogen supply from dairy effluents are highly variable, highlighting the importance of testing individual effluents. It also found that most of the short term nitrogen supply (0 – 6 months) comes from the inorganic nitrogen (immediately available to crops) present in the effluent at the time of application. Finally, the study identified some potentially useful measures to predict nitrogen supply.

The research conducted under this programme has contributed to a set of industry guidelines on using effluents to grow crops. 

This study was conducted in collaboration with AgResearch, as part of the DairyNZ-led Forages for Reduced Nitrate Leaching (FRNL) MBIE programme to help farmers create ‘closed-loop’ nutrient management systems, reducing the need for synthetic fertiliser while making better use of recyclable resources on farm. 


Journal Reference:

Norris, M, Johnstone, P, Dexter, M, Selbie, D, Houlbrooke, D, Sharp,J, Hedderley, D. Predicting nitrogen supply from dairy effluent applied to contrasting soil types. New Zealand Journal of Agricultural Research 62 (4). DOI:10.1080/00288233.2018.1508478

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