Nitrogen Turnover on Organic and Conventional Mixed Farms

Separate focus on crop fertilization or feeding practices inadequately describes nitrogen (N) loss from mixed dairy farms because of (1) interaction between animal and crop production and between the production system and the manager, and (2) uncertainties of herd N production and crop N utilization. Therefore a systems approach was used to study N turnover and N efficiency on 16 conventional and 14 organic private Danish farms with mixed animal (dairy) and crop production. There were significant differences in N surplus at the farm level (242 kg. N/ha. vs. 124 kg. N/ha. on conventional and organic dairy farms respectively) with a correlation between stocking rate and N surplus. N efficiency was calculated as the output of N in animal products divided by the net N import in fodder, manure and fertilizer. N turnover in herd and individual crops calculated on selected farms showed differences in organic and conventional crop N utilization. This is explained via a discussion of the rationality behind the current way of planning the optimum fertilizer application in conventional agriculture. The concept of marginal N efficiency is insufficient for correcting problems of N loss from dairy farms. Substantial reductions in N loss from conventional mixed dairy farms is probably unlikely without lower production intensity. The concept of mean farm unit N efficiency might be a way to describe the relation between production and N loss to facilitate regulation. This concept is linked to differing goals of agricultural development — i.e. intensification and separation vs. extensification and integration. It is discussed how studies in private farms — using organic farms as selected critical cases — can demonstrate possibilities for balancing production and environmental concern

Malkekvæg som dynamo for en alsidig udvikling af økologisk jordbrug

I kapitlet beskrives tre produktionssystemer, som har kørt på Den Økologiske Forsøgsstation Rugballegård gennem tre år: 1) Mælkeproduktion, 2) Svineproduktion samt 3) Kombineret produktion af svin og kvæg, hvor køerne tildeles et reduceret niveau af tilskudsfoder. Kvægbesætningen blev således delt i to hold: N på normalt foderniveau, som afspejlede det rene mælkeproduktionssystem; og L på lavt foderniveau, som afspejlede kombinationssystemet, hvor det energirige foder blev brugt til svineproduktionen. Systemerne er beskrevet gennem modelberegninger og gennem resultater fra Rugballegård. Modelberegningerne viser den højeste gennemsnitlige afgrødeproduktion på 5650 kg ts per ha i kvægsædskiftet (tilhørende malkekvæg på normalt foderniveau) mod 3250 kg ts per ha i svinesædskiftet (tilhørende produktionen af søer og slagtesvin) og 5150 kg ts per ha i det kombinerede kvæg-svinesædskifte (Malkekvæg lavt foderniveau, søer og slagtesvin). Modelberegningen viser, at forskellene primært er knyttet til sammensætningen af sædskiftet og niveauet af plantetilgængeligt kvælstof, samt at kombinationssystemet (kvæg/svin integreret) indebærer synergieffekter omkring især sædskiftet og næringsstofudnyttelsen. Den observerede produktion i systemerne afveg ikke betydende fra det forventede. Når malkekøerne blev fodret med grovfoder alene, blev intervallet mellem 1. og 2. kælvning øget og mælkens teknologiske kvalitet generelt forringet, mens der ikke var indikationer af sygdomsproblemer forbundet med det reducerede foderniveau

Estimated N leaching losses for organic and conventional farming in Denmark

The impact of organic compared to conventional farming practices on N leaching loss was studied for Danish mixed dairy and arable farms using an N balance approach based on representative data. On mixed dairy farms a simple N balance method was used to estimate N surplus and N leaching loss. On arable farms the simple N balance method was unreliable due to changes in the soil N pool. Consequently, the FASSET simulation model was used to estimate N surplus, N leaching loss and the changes in the soil N pool. The study found a lower N leaching loss from organic than conventional mixed dairy farms, primarily due to lower N inputs. On organic arable farms the soil N pool was increasing over years but the N leaching loss was comparable to conventional arable farms. The soil N pool was primarily increased by organic farming practices and incorporation of straw. The highest increase in the soil N pool was seen on soils with a low level of soil organic matter. The level of N leaching loss was dependent on soil type, the use of catch crops and the level of soil organic matter, whereas incorporation of straw had a minor effect. N leaching was highest on sandy soils with a high level of soil organic matter and no catch crops. The study stresses the importance of using representative data of organic and conventional farming practices in comparative studies of N leaching loss

Potentialet for omlægning til økologisk jordbrug i Danmark

Potentialet for omlægning til økologisk jordbrug i Danmark

Comparative environmental assessment of three systems for organic pig production in Denmark

Organic pig production has emerged as an alternative to the intensive conventional pig production in Europe with the animals confined indoors and often an imbalance between livestock and land for feed production and manure utilisation. The organic systems aim at improving animal welfare by supporting the pig’s natural behaviour (Hermansen et al., 2003), and improving soil fertility by better linking crop and livestock production from an agro-ecological point of view. The differences between organic and conventional pig production is more fundamental than for example differences between dairy production systems, which may be why the share of pig herds within the organic holdings is considerably lower than the percentage of pig herds in conventional agriculture in both the UK (ADAS, 2001), Germany (Willer, et al., 2002) and Denmark (Plant Directorate, 2004b). However, the recent development has seen a dramatic increase in demand for organic pig meat in Denmark, Germany and the UK and present production cannot meet demand. Besides regulation on use of feedstuffs, the organic pig production has a main challenge in the regulation for housing. The sows need access to grazing in the summer time, and growing pigs need as a minimum requirement access to an outdoor run. In addition, the area requirements for indoor housing are higher than for conventional production. These requirements have a major impact on what systems to consider, both from economical and agro-ecological points of view. And therefore, efforts to improve organic pig production should focus on the integration of livestock production and land use, but considering environmental impacts on local and global scales. The most commonly used system in Denmark is to combine an outdoor sow production all year round with rearing growing pigs in barns with an outdoor run (Hermansen & Jakobsen, 2004). The type of stable most commonly used by full time producers in Denmark is a system with deep litter in the entire indoor area or deep litter/straw bed in half the area while the outdoor area consists of a concrete area. The use of a concrete covered area, from which the manure can be collected, is a way to comply with the environmental regulations stating that the outdoor run should be constructed in a way that prevents leaching. Research shows that very good production results can be obtained in such systems in terms of litter size, daily gain, feed consumption and health (Hermansen et al., 2003). However, two possible drawbacks exist. First, the space requirement per growing pig in housing facilities is considerable and, thus, capital demanding. For fattening pigs of 85-100 kg live weight, the indoor space required is equivalent to 1.3 m2/pig (of which at least 0.65 m2 must consists of a solid floor) and 1.0 m2 outdoors run (Council Regulation, 1999). In addition, each lying zone, i.e. straw bedding area, must be able to accommodate all pigs at a time. This put a heavy burden on costs of buildings (money and resource use) and at the same time it can be questioned if such rearing systems comply with the consumer expectations. Second, the outdoor sow production has been connected with high environmental burden in the form of N losses (Larsen et al., 2000; Eriksen et al., 2002). This made us to consider two alternatives to the organic pic system most often used presently. A system where all pigs were reared outdoors on grassland (and saving buildings) and a system where sows and growing pigs were kept in a tent system placed upon a deep litter area in order to reduce risk for N leaching. Both have been used under commercial conditions. In order to assess the possible trade-offs between environmental impacts on the one hand and the assumed advantages of these alternative systems (animal welfare, low investment) on the other hand an Environmental Impact Assessment was needed. Environmental assessment of livestock farming systems can be done on an area basis (e.g. nutrient losses per ha) or on a product basis (e.g. Green House Gas emission per kg meat or milk; Haas et al., 2001; van der Werf & Petit, 2002; De Boer, 2003; Halberg et al., 2005). The area based assessment is relevant for locally important emissions such as nitrate leaching but a product based assessment is more relevant for emissions, which have a less localised impact (acidification) or even a global character (Green House Gasses). Moreover, since the organic production is often considered a more sustainable alternative to conventional intensive pig production, from a consumer point of view it might be interesting to compare the eutrophication per kg meat produced from different organic and compared to conventional systems. The objective of this paper is to compare the environmental impact and green house gas emission of organic pig production systems with different levels of integration of livestock and land use

Impact of organic pig production systems on CO2 emission, C sequestration and nitrate pollution

Organic rules for grazing and access to outdoor area in pig production may be met in different ways, which express compromises between considerations for animal welfare, feed self-reliance and negative environmental impact such as greeehouse gas emissions and nitrate pollution. This article compares environmental impact of the main organic pig systems in Denmark. Normally sows are kept in huts on grassland and finishing pigs are being raised in stables with access to an outdoor run. One alternative practised is rearing also the fattening pigs on grassland all year round. The third method investigated was a one-unit pen system mainly consisting of a deep litter area under a climate tent and with restricted access to a grazing area. Using life cycle assessment (LCA) methodology, the emissions of greenhouse gasses of the all free range system was estimated to be 3.3 kg CO2-equivalents kg-1 liveweight pig, which was significantly higher than the indoor fattening system and the tent system yeilding 2.9 and 2.8 kg CO2-eq. kg-1 pig respectively. This was 7-22% higher compared with Danish conventional pig production but, due to the integration of grass-clover in the organic crop rotations these had an estimated net soil carbon sequestration. When carbon sequestration was included in the LCA then the organic systems had lower green house gas emissions compared with the conventional pig production. Eutrophication in nitrate equivalents per kg pig was 21-65% higher in the organic pig systems and acidification was 35-45% higher per kg organic pig compared with the conventional system. We conclude that even though the all free range system theoretically has agro-ecological advantages over the indoor fattening system and the tent system due to a larger grass-clover area this potential is difficult to implement in practice due to problems with leaching on sandy soil. Only if forage can contribute a larger proportion of the pigfeed-uptake may the free range system be economically and environmentally competitive. Improvement of nitrogen cycling and efficiency is the most important factor for reducing the overall environmental load from organic pig meat. Presently a system with pig fattening in stables and concrete covered outdoor runs seems to be the best solution from an environmental point of view

Kvælstofregnskaber på husdyrbrug

At begrænse tabet af nærringsstoffer til det omgivende miljø indgår som en del af mange landmænds mål for god driftledelse. Det er vanskeligt at måle eller beregne det faktiske tab af kvælstof fra husdyrbedrifter, og der findes endnu ingen modeller, som kan beregne de enkelte tabsposter rimeligt præcist og samtidigt redegør for den samlede omsætning af kvælstof (N) på bedriften. Separate opgørelser af udnyttelse og tab af N fra enten besætning eller marker giver et mangelfuldt billede af bedriftens reelle udnyttelse af N. Derimod kan en beregning af en husdyrbedrifts samlede omsætning og overskud af N give et godt udtryk for det potentielle N-tab til det omgivende miljø. Ved DJF er der i flere år udført analyser af N-omsætningen og N-udnyttelse i forskellige typer husdyrbrug gennem en kombination af studier i private bedrifter og modellering. Det er også undersøgt hvilke muligheder, driftslederen har for at påvirke bedriftens N-overskud, og hvordan sådanne N-regnskaber kan indgå i styringen af bedriften. Denne Grøn Viden beskriver N-regnskaber for 3 bedrifter som eksempler på metodens anvendelse og diskuterer resultater fra samarbejde med 20 bedrifter

Græs i sædskiftet - effekt af afstande og belægning

Udviklingen inden for den økologiske kvægproduktion resulterer i større bedrifter. En ofte afledt effekt af udviklingen er, at afgræsning med malkekøer ikke er mulig på en del bedriftens arealer pga. store afstande og eller fysiske forhindringer i form af veje mellem mark og stald-faciliteter, hvorfor det er en særlig udfordring at udnytte græsmarken via afgræsning og at sikre en hensigtsmæssig placering af græsmarkerne i sædskiftet til sikring af bedriftens produktion, økonomi og næringsstofomsætning. Til understøttelse af den strategiske rådgivning og beslutningstagen er der derfor udarbejdet et modelværktøj med fokus på denne problemstilling. I det følgende er beskrevet model forudsætninger og vist enkelte resultater af udvalgte scenarier. Modellen er stadigvæk under udvikling og test, så de endelige beregninger kan afvige lidt fra de viste

Indirekte beregning af N-fiksering

Indirekte beregning af N-fiksering dels ud fra målt udbytte af bælgplantetørstof, dels ud fra bedømt kløverdækning og dels ud fra ukendt kløverandel