FARMFLOW—A dynamic model for phosphorus mass
ﬂow, simulating conventional and organic management
of a Swedish dairy farm
, Ingrid O
born, Harald Sverdrup
Department of Chemical Engineering, Lund Institute of Technology, P.O. Box 124, SE-221 00 Lund, Sweden
Received 24 August 2005; received in revised form 16 October 2006; accepted 10 November 2006
A farm systems mass-balance calculation model, FARMFLOW, was applied to a case study comparing organic and conventional
management of a Swedish experimental dairy farm, O
jebyn. Parameterisation of the model is implemented using detailed ﬁeld data from
jebyn farm where the two management systems have been run parallel for more than 11 years. Simulations were made to compare
the stocks, ﬂows and resulting balances of phosphorus (P) in the two systems during six crop rotations (36 years). In addition, a maxi-
mum animal density scenario was tested, in order to analyse the eﬀects of increased production intensity. Results show that FARM-
FLOW can be a useful tool for analysing the impact of management on internal farm P dynamics, as well as imports and exports.
The organic management results in a higher proportion of internal P ﬂows whereas the conventional system relies more on imports
of P in feed and mineral fertilisers. In both management systems, the crop rotation cause large temporal and spatial variation in the
application of manure P to the soil system. The resulting ﬁeld speciﬁc soil P accumulation can indicate which ﬁelds to target with changed
fertilisation management. In the maximum animal density scenario, both management systems led to an application rate of manure P in
excess of crop demands.
Ó 2006 Elsevier Ltd. All rights reserved.
Keywords: Mass-balances; Dairy farming; Phosphorus (P); Management
Nutrient balance calculations are widely used to increase
nutrient eﬃciency and reduce losses from agricultural
born et al., 2003). There are several account-
ing systems for nutrients in Europe, many of which are
computer based (Goodlass et al., 2003). The nutrient
accounting can be compulsory or mandatory. For example,
Swedish organic farmers are required to make nutrient bal-
ance calculations (KRAV, 2004) and many conventional
dairy farms are registered in voluntary environmental
and certiﬁcation programmes with nutrient management
requirements (Swensson, 2003). The wide use of accounting
systems and balance calculation methods can be attributed
to their relative simplicity, as the most common approach
is to make an import–export balance, i.e. to count the
nutrients following the cash ﬂows of the farm that are usu-
ally recorded anyway in the economic book-keeping
(Goodlass et al., 2003). From a farmer perspective, the
farm gate approach can provide a good indication of nutri-
ent imbalances at a reasonable eﬀort. In addition to the
comparative ease by which farm gate balances can be made
and communicated, such indicators can be standardised
and used to compare performance (Halberg et al., 2005).
However, in many nutrient accounting systems the simula-
tion is limited to one year, making the evaluation of the
long-term eﬀects of imbalances on the farm diﬃcult. In
addition, using a farm gate perspective means that the
internal stocks and ﬂows of nutrients are unaccounted
for (Goodlass et al., 2003).
0308-521X/$ - see front matter Ó 2006 Elsevier Ltd. All rights reserved.
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Agricultural Systems 94 (2007) 431–444