ARS | Publication request: Nitrogen Use Efficiency in Dairy Production

Submitted to: Nitrogen Workshop Proceedings
Publication Type: Proceedings
Publication Acceptance Date: May 22, 2009
Publication Date: June 29, 2009
Citation: Powell, J.M., Rotz, C.A., Weaver, D.M. 2009. Nitrogen Use Efficiency in Dairy Production. In: Grignani, C., Acutis, M., Zavattaro, L., Bechini L., Bertora, C., Marino Gallina, P., Sacco, P., editors. Proceedings of the 16th Nitrogen Workshop - Connecting different scales of nitrogen use in agriculture, June 28 - July 1, 2009, Turin, Italy. p. 241-242.

Interpretive Summary: Nitrogen use efficiency is a general term used to describe the relative amount of nitrogen input, such as feed, fertilizer, and manure that is converted into products, such as milk, crops or pasture. Dairy cows and crops/pastures have limited capacities to utilize nitrogen inputs. Most feed nitrogen is excreted in manure and fertilizer/manure nitrogen is stored in soil or lost to the environment. We describe the factors and processes that impact nitrogen use efficiency on dairy farms and practices that farmers may adopt to simultaneously enhance nitrogen use efficiency, profitability and the environmental outcomes of their farms.

Technical Abstract: Escalating prices of feed and fertilizer, and increasing regulations to reduce environmental contamination due to nitrogen (N) loss have created new pressures to improve N use efficiency (NUE) on dairy farms. The purpose of this paper is to provide an overview of relative NUE for (1) feed conversion into milk, (2) fertilizer and manure incorporation into crops and pastures, and (3) the whole farm. Feed NUEs are generally higher on confinement dairy farms (26% to 33%) than on grazing-based dairy farms (16% to 24%). Fertilizer+manure NUEs (16% to 78%) depend on dairy herd management, amount and method of manure application, timing of application, and nutrient demands of the subsequent crop/pasture. The highest NUE is generally obtained when manure N is applied with fertilizer N at agronomic rates. Whole-farm NUEs range from 14% to 55%. A common feature of all NUEs is that the highest values are associated with the lowest N inputs, and vice-versa. Surplus N in dairy production can be divided into three components: (1) inherent biological inefficiency of N incorporation into products, (2) N application to avoid risk, and (3) N application wastage. Dairy farmers can do little about the inherent biological inefficiency in which feed N is incorporated into milk, and fertilizer and manure N are incorporated into crops and pasture. Following recommendations can enhance NUEs and profits, and reduce the negative environmental impacts of dairy farms.