Innovative Technology and Sustainable Development of Organic - 1.
Innovative Technology and Sustainable Development of Organic - 1.
Innovative Technology and Sustainable Development of Organic - 1.
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Indicators were expressed per dairy cow, to be able to compare values among farms. Economic data<br />
were derived directly from the farmer’s economic accounts, authorized by a registered public<br />
accountant.<br />
3.2.5 Eutrophication<br />
On-farm eutrophication can be quantified by input–output accounting <strong>of</strong> nitrogen (N) <strong>and</strong> phosphorus<br />
(P), which is reported to be relevant <strong>and</strong> reliable (Mollenhorst et al., 2006). By input–output accounting<br />
<strong>of</strong> nutrients, one can determine the nutrient surplus, which is assumed to be lost to the environment. In<br />
this research, we computed both a farm <strong>and</strong> field nutrient balance. The farm balance determines the<br />
average N <strong>and</strong> P surplus per hectare <strong>of</strong> farmed l<strong>and</strong> (Thomassen <strong>and</strong> De Boer, 2005; Halberg et al.,<br />
2005). In order to quantify the effect <strong>of</strong> overstocking on eutrophication <strong>of</strong> individual fields, we also<br />
computed a nitrogen balance for specific individual fields, representing grazing pasture <strong>and</strong> pasture for<br />
mowing, determining the N surplus in kg per hectare <strong>of</strong> field per year. The P balance <strong>of</strong> individual<br />
fields was not determined, because the estimated P surplus at farm level appeared to be low, which<br />
corresponds to other registrations in Denmark (Hvid et al., 2004).<br />
The NP input at farm level was determined by quantifying input through imported feed (i.e.,<br />
roughage, concentrates, <strong>and</strong> other feeds), mineral supplements, manure, <strong>and</strong> livestock. In addition, the<br />
N fixation <strong>of</strong> fields through pulses <strong>and</strong> grass–clover was computed using empirical data from. We<br />
assumed N fixation in grass–clover ley <strong>of</strong> 18 kg/ha per year for a clover percentage between 1% <strong>and</strong><br />
9%, <strong>of</strong> 78 kg/ha per year for a percentage between 10% <strong>and</strong> 29%, <strong>of</strong> 156 kg/ha per year for a<br />
percentage between 30% <strong>and</strong> 49%, <strong>and</strong> <strong>of</strong> 248 kg/ha per year for a percentage >49% (Kristensen <strong>and</strong><br />
Kristensen, 1992). The percentage <strong>of</strong> clover was estimated visually by one observer. N fixation for<br />
pulses was assumed to be 80 kg N/ha per year. Atmospheric N deposition was assumed to be the same<br />
for AMS <strong>and</strong> CMS farms, 16 kg N/ha per year (Ellermann et al., 2005). The NP output was determined<br />
by quantifying the amounts <strong>of</strong> sales <strong>of</strong> milk <strong>and</strong> livestock, manure, feedstuffs, <strong>and</strong> crops. St<strong>and</strong>ard<br />
concentrations <strong>of</strong> N <strong>and</strong> P were used (Poulsen et al., 2001). The N content <strong>of</strong> milk, as well as the<br />
amount <strong>of</strong> milk, was taken from the milk delivery registration. A st<strong>and</strong>ard P content <strong>of</strong> milk was<br />
assumed. The difference between the NP input <strong>and</strong> NP output determined the NP surplus, <strong>and</strong> was<br />
expressed per hectare <strong>of</strong> farmed l<strong>and</strong>.<br />
The field balance was determined only for fields that were fully used for mowing or grazing. The N<br />
surplus per hectare <strong>of</strong> field balance was computed as the difference between the N input <strong>and</strong> N output.<br />
The N input for each hectare was estimated by computing the amount <strong>of</strong> N applied by manure, the<br />
amount <strong>of</strong> N deposited via feces <strong>and</strong> urine during grazing, <strong>and</strong> the N fixation <strong>and</strong> deposition. The<br />
amount <strong>of</strong> manure applied was registered in the farmers’ obligatory mineral account for each hectare <strong>of</strong><br />
l<strong>and</strong>. In order to estimate the amount <strong>of</strong> N deposited via feces <strong>and</strong> urine during grazing, information<br />
about the grazing time (hours per day <strong>and</strong> days per year) <strong>and</strong> stocking rate was acquired from the<br />
farmer. Using empirical data for excretion <strong>of</strong> N per cow based on measured milk yield on yearly basis<br />
<strong>and</strong> milk urea content (Jonker et al., 1998) <strong>and</strong> deposition related to grazing time (Oudshoorn et al.,<br />
2008), the amounts were calculated as shown in Equation <strong>1.</strong><br />
Used timeoutside(h/day)<br />
� Totalexcretion<br />
in kg N/cowday<br />
�stockingrate�<br />
daysgrazing<br />
[1]<br />
24 h<br />
N-fixation <strong>and</strong> N deposition were computed in a similar way as for the farm gate balance.<br />
Thesis Frank W. Oudshoorn 43