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ARS Home » Midwest Area » Madison, Wisconsin » U.S. Dairy Forage Research Center » Dairy Forage Research » Research » Publications at this Location » Publication #331790
Title: Nitrogen use efficiency goals in dairy production systems: -a review and case study examples

Author
item DEKLEIN, C. A. M. - Agresearch
item MONAGHAN, R. M. - Agresearch
item ALFARO, M. - Inia Carillanca
item GOURLEY, C. - Department Of Primary Industries
item OENNEMA, O. - Wageningen University
item Powell, Joseph

Submitted to: International Nitrogen Conference
Publication Type: Proceedings
Publication Acceptance Date: 9/9/2016
Publication Date: N/A
Citation: N/A

Interpretive Summary:

Technical Abstract: Nitrogen use efficiency (NUE), the ratio between N outputs in products over N inputs, is often used to evaluate N use outcomes of an agricultural system and the risk of environmental N loss. In this paper we address the question what realistic NUE goals can be targeted for dairy production systems? We use the following definitions of NUE: Crop NUE, defined as the percentage of the total N inputs taken up by crops or pasture; Animal NUE, defined as the percentage of total feed N intake incorporated into milk; and Whole farm NUE, defined as N exported in animal products and/or exported feed, as a percentage of total N inputs to the farm. Nitrogen surpluses (i.e. N inputs minus N outputs) are also reviewed. Published values of Crop NUE and N surplus generally ranged between 55-90% and 25-230 kg N/ha/year, respectively, while commonly reported Animal NUE and N surplus values ranged between 15-35% and 110-450 kg N/ha/year. Whole farm NUE and N surplus values ranged between 10-65% and 40-700 kg N/ha/year. In NZ Whole farm NUE was affected more strongly by differences between catchments (e.g. soil and climatic conditions) than by differences in management. In contrast, N surplus values differed both between-catchment and within-catchment and were good indicators of N losses to water. Realistic goals for NUE will therefore depend on the agro-climatic context in which a dairy production system operates and the impacts the goals are aiming to manage. Crop and Animal NUE values can be valuable indicators for optimizing fertilizer and feed use and minimizing N losses. However, global or even national Whole-farm NUE values appear to be of limited value if the ultimate goal for setting NUE targets is to reduce the environmental impact of N use. Whole-farm level targets based on N surplus would be a more useful indicator for this. Regardless of the metric used, all metrics are calculated based on estimates of N inputs and N outputs, so it is critically important that all inputs and outputs are measured or adequately estimated. Any NUE goals should be set in the context of other agro-environmental indicators such as losses of phosphorus and fecal organisms to water, carbon footprints, and energy and water use efficiencies.