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

Document Type

Conference Proceeding

Publication Date

2011

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.

Keywords

nitrogen, phosphorus, nutrient balance, nutrient efficiency, dairy

Disciplines

Agriculture | Dairy Science | Natural Resources and Conservation | Natural Resources Management and Policy | Other Nutrition | Soil Science | Water Resource Management

Abstract

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.

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