Improving the nutrient status of a commercial dairy farm: An integrated approach

D. H. Lynch^1*, R. W. Jannasch³, A. H. Fredeen² and R. C. Martin¹

Abstract
Minimizing nutrient surpluses and improving efficiency of nutrient use is a key challenge for all dairy farming production systems, driven by economic, environmental and increasing regulatory constraints. Our study examined the efficiency of N, P and K use on a commercial dairy farm through an integrated approach that evaluated the nutrient status of all aspects of the production system of the case study farm, a 75 lactating Holstein cow dairy in Kings County, Nova Scotia, Canada.

During the decade after 1988, the farm owner implemented a series of changes in production practices, including diversification of the crop rotation, implementation of a management intensive grazing (MIG) regime and adoption of a systematic approach to soil and nutrient management. Milk production, and associated farm exports of N, P and K, increased 666 kg per cow between 1990 and 2000. Purchases of N-P-K fertilizers were eliminated in 1990 and feed nutrient imports were dramatically reduced. Feed costs per litre of milk declined from 14.3 cents (CDN)/litre in 1990-92 to 11.6 cents/litre in 1998-2000 even as feed prices increased regionally by 10-20% over the same period.

Modelling of current whole farm mass N, P and K balance indicated 25.0% of all N inputs are recovered in farm products, milk and meat. Non-legume derived field N input (67 kg N ha-1 before losses) was close to optimum for the predominantly legume/grass based forage cropping system. Model determined annual farm nutrient surpluses (outputs-inputs) for P (9.0 kg ha-1 yr-1) and K (8.2 kg ha-1 yr-1) were significantly lower than those previously reported for regional confinement-based dairy farms which were more reliant on corn production.

However, data from 16 years of soil analysis (1985-2001) indicated an increase in soil test P levels of approximately 2 mg kg-1 per year. Recent refinements in dairy animal dietary P levels have further reduced the farm P surplus (2.6 kg ha-1 in year 2001) and are shown as key to a strategy for reversal of the trend in soil test P levels.

In summary, the combined approach of whole-farm system nutrient management, crop diversification and MIG increased milk production and minimized costs while reducing farm nutrient inputs. The study demonstrates how an approach to dairy farm nutrient management which integrates livestock and crop nutrient requirements may reduce dairy farm nutrient loading while maintaining productivity.

Source
American Journal of Alternative Agriculture (2003) 18: 137-145


Author Locations and Affiliations
(1) Organic Agriculture Centre of Canada (OACC) located at the Nova Scotia Agricultural College (NSAC), PO Box 550, Truro, Nova Scotia, Canada B2N 5E3
(2) Department of Plant and Animal Science, NSAC, PO Box 550, Truro, Nova Scotia, Canada B2N 5E3
(3) Resource Efficient Agricullural Production (REAP), Box 126, Ste. Anne de Bellevue, Quebec, Canada H9X 3V9
* Corresponding author, E-mail dlynch@nsac.ca


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