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Research article - Peer-reviewed, 2011

Dairy farm nutrient management model. 2. Evaluation of different strategies to mitigate phosphorus surplus

Huhtanen, Pekka; Turtola, Eila; Nousiainen, Juha


To reduce (P) surpluses on dairy farms and thereby the risk of P losses to natural waters we studied different management alternatives by a nutrient balance model described in the companion paper. The strategies evaluated mitigating the P surpluses were: mineral P fertilisation, dietary mineral P supplementation, replacement rate, animal density, production level, feeding intensity, dietary P concentration and nutrient efficiency in crop production. Responses to several interventions (e.g. mineral P fertilisation, purchased feed P, replacement rate) were similar to those observed in Finnish field studies. Reducing or completely giving up the use of purchased mineral P fertilisers was the most efficient measure to reduce P surplus. The slope between the amount of mineral fertilisers and P surplus was 0.98-0.99 (in the field data 1.0). Increased animal density resulted in a greater P surplus, but the slope between P input from purchased feed and surplus was considerably smaller (0.65) than that of P fertilisation. Increasing milk yield with improved genetic potential of the cows would have minimal effects on P surplus per unit of product, but it would increase P surplus per hectare. When the intensity of energy and protein feeding was increased, P surplus rose markedly both per unit of product and hectare. This is (1) due to increased dietary P concentration and (2) due to smaller marginal production responses than those calculated from feeding standards. Reducing dietary P concentration by constraining P excess per kg milk in least-cost ration formulation improved P efficiency in milk production and dairy farming system. However, feed cost increased as low P energy (sugar-beet pulp) and protein (soybean meal) supplements are more expensive than cereal grains or rapeseed feeds. Improving the nutrient use efficiency in crop production had a strong influence in the whole-farm efficiency and P surplus. The modelling results showed that Finnish dairy farms have a great potential to improve P efficiency and reduce P losses to the environment, even by increasing production intensity (milk/ha). It is concluded that the most cost-effective scenario to mitigate P surpluses at a dairy farm would be to reduce or give up the use of mineral P as fertilisers and supplements, and to improve the use of present soil P reserves. (C) 2011 Elsevier Ltd. All rights reserved.

Published in

Agricultural Systems
2011, Volume: 104, number: 5, pages: 383-391

    SLU Authors

    • Huhtanen, Pekka

      • Department of Agricultural Research for Northern Sweden, Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Animal and Dairy Science
    Environmental Sciences related to Agriculture and Land-use
    Veterinary Science

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