Nitrogen And Phosphorus Balances And Efficiencies On Contrasting Dairy Farms In Australia

Document Type

Conference Proceeding

Publication Date


Conference Title

In: Adding to the knowledge base for the nutrient manager. (Eds L.D. Currie and C L. Christensen). http://flrc.massey.ac.nz/publications.html. Occasional Report No. 24. Fertilizer and Lime Research Centre, Massey University, Palmerston North, New Zealand. 16 pages.


nitrogen, phosphorus, nutrient balance, nutrient efficiency, dairy


Nitrogen (N) and phosphorus (P) imports, exports and within-farm flows were measured during a standardised production year on 41 contrasting Australian dairy farms, representing a broad range of geographic locations, productivity, herd and farm size, reliance on irrigation, and soil types. The amount of N and P imported varied markedly, with feed and fertiliser generally the most significant contributors and principally determined by stocking rate and type of imported feed. Whole-farm N surplus ranged from 47 to 600 kg N/ha/year and was strongly (P < 0.01) and linearly related to the level of milk production. Whole-farm N use efficiency ranged from 14 to 50%, with a median of 26%. Whole-farm P surplus ranged from -7 to + 133 kg P/ha/year, with a median of 28 kg/ha. Phosphorus use efficiencies ranged from 6 to 158%, with a median of 35%. The poor relationship between P fertiliser inputs and milk production from home-grown pasture and crops reflected the high soil P levels measured on these farms. The N and P intakes of each dairy herd, the locations the cows visited and the time they spent there, were also determined during five visits throughout the year. As N and P intakes increased so did excreted N and P, with use efficiencies generally less than 20%. On average 432 g N and 61 g P were excreted by each lactating dairy cow/day. Overall, cows spent a small proportion of their time in the milking parlour (2%) and yards (9%) where dung and urine were generally collected; however, greater time was spent on feedpads (11%) and holding areas (26%) where manure was not routinely collected. The largest amounts of excreted N and P were deposited by cows in grazed paddocks but particularly those closest to the milking parlour. Key opportunities to improve N and P use efficiency within grazed dairy systems include reducing unnecessary nutrient intake; improved spatial and temporal movement of animals within dairy farms to reduce heterogeneous N and P deposition; increasing the capture, storage and redistribution of excreted N and P in non-productive areas, and more strategic fertiliser and effluent applications.