Researching Sustainable Agricultural Systems, ISOFAR 2005
Editorial
Editorial: Exploring organic agriculture's place within the agricultural revolution
- Martin H. Entz, Daniel Neuhoff, William Lockeretz
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- 25 February 2008, pp. 1-2
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Research Papers
Grain legume–cereal intercropping: The practical application of diversity, competition and facilitation in arable and organic cropping systems
- Henrik Hauggaard-Nielsen, Bjarne Jørnsgaard, Julia Kinane, Erik Steen Jensen
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- 25 February 2008, pp. 3-12
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Intercropping is the simultaneous cultivation of more than one crop species on the same piece of land and is regarded as the practical application of basic ecological principles such as diversity, competition and facilitation. Field experiments were carried out on a sandy loam soil and a sandy soil in Denmark over three consecutive cropping seasons including dual grain legume (pea, faba bean and lupin)–barley intercropping as compared to the respective sole crops (SC). Yield stability of intercrops (IC) was not greater than that of grain legume SC, with the exception of the IC containing faba bean. Faba bean and lupin had lower yield stability than pea and fertilized barley. However, the different IC used environmental resources for plant growth up to 50% (LER=0.91–1.51) more effectively as compared to the respective SC, but with considerable variation over location, years and crops. The SC performance supported the interspecific interactions within the IC stand. On the sandy loam 13% greater grain yield of pea cv. Agadir (520 g m−2) was observed as compared to cv. Bohatyr. Faba bean and lupin yielded similarly (340 g m−2) in the sandy loam soil, with decreasing yields on the sandy soil (320–270 g m−2). Nitrogen fixation was very constant in grain legume SC over species and location, varying from 13.2 to 15.8 g N m−2, being lowest in peas and highest in faba bean and lupin. The intercropped grain legumes increased the proportion of plant N derived from N2-fixation by on average 10–15% compared to the corresponding SC. However, especially lupin was suppressed when intercropping, with a reduced N2-fixation from 15 to 5–6 g N m−2. The IC were particularly effective at suppressing weeds, capturing a greater share of available resources than SC. Weed infestation in the different crops was comparable; however, it tended to be the highest in sole cropped faba bean, lupin and unfertilized barley, where the application of urea to barley reduced the weed infestation by around 50%. Reduction in disease was observed in all IC systems compared to the corresponding SC, with a general disease reduction in the range of 20–40%. For one disease in particular (brown spot on lupin) disease reduction was almost 80% in the IC. Intercropping practices offer many advantages but improved understanding of the ecological mechanisms associated with planned spatial diversity, including additional benefits with associated diversity, is needed to enhance the benefits achieved.
Strategies to control Canada thistle (Cirsium arvense) under organic farming conditions
- Pavel Lukashyk, Martin Berg, Ulrich Köpke
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- 25 February 2008, pp. 13-18
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Three strategies for controlling Cirsium arvense including (i) repeated stubble tillage with subsequent forage crop cultivation, (ii) repeated mowing of a ryegrass–clover ley and (iii) forage crop cultivation following a ryegrass–clover ley ploughed in May/June were investigated in field experiments over 3 years at the Experimental Farm for Organic Agriculture ‘Wiesengut’ in North-Rhine Westphalia, Germany. The development of C. arvense (shoot density, shoot size and ground cover) was regularly assessed on fixed standardized subplots. In the medium-term (9 months), repeated stubble tillage (i) decreased shoot density and regrowth capacity of C. arvense more effectively than a mowed ryegrass–clover ley (ii and iii). However, after 22 months, strategies (i) and (ii) resulted in a similar strong reduction of C. arvense shoot density of 95 and 97%, respectively. At this time, the efficacy of strategy (iii) (89%) was not significantly different to that of strategies (i) and (ii). After 26 months, the effect of all strategies was still apparent; however, the efficacy of strategy (iii) was significantly lower than that of strategy (ii). Generally, the different strategies showed only minor differences, thus delivering options for optimal strategies of thistle control under given specific conditions of sites and cropping systems.
Tanniferous forage plants: Agronomic performance, palatability and efficacy against parasitic nematodes in sheep
- D.A. Häring, A. Scharenberg, F. Heckendorn, F. Dohme, A. Lüscher, V. Maurer, D. Suter, H. Hertzberg
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- 25 February 2008, pp. 19-29
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Tanniferous forage plants can have beneficial effects on ruminant productivity and health (improved protein supply, bloat safety and antiparasitic properties). However, condensed tannins can also lower palatability, voluntary feed intake and digestibility. The aim of our interdisciplinary project was to generate basic knowledge on plant management, feed palatability and the antiparasitic properties of tanniferous forage plants for their practical application in agronomy, focusing on their usefulness in controlling gastrointestinal nematodes in organic farming. We found that Onobrychis viciifolia (sainfoin), Lotus corniculatus (birdsfoot trefoil) and Cichorium intybus (chicory) were suitable for cultivation under the given temperate climatic conditions, whereas Lotus pedunculatus (big trefoil) was soon outcompeted by unsown species. Growing the tanniferous plant species in a mixture with Festuca pratensis (meadow fescue) rather than in a monoculture had the advantage of increasing total dry matter (DM) yield (especially in the case of tanniferous legumes) and of reducing the DM proportions of unsown species. However, due to dilution by non-tanniferous F. pratensis, the tannin concentrations of mixtures were clearly lower and the seasonal fluctuations in tannin concentrations greater than that of monocultures. Across species, tannin concentrations were highest for O. viciifolia, followed by L. corniculatus and very low for C. intybus. Palatability of all tanniferous forages was comparable to that of a ryegrass/clover mixture when fed as dried forage and, when offered as silage, palatability of O. viciifolia was clearly superior to that of the respective ryegrass/clover control. Administration of dried or ensiled O. viciifolia reduced parasite egg counts in feces of lambs co-infected with the gastrointestinal nematode species Haemonchus contortus and Cooperia curticei. We conclude that O. viciifolia is the most promising among the tested tanniferous forage plant species due to its suitability for cultivation, its high tannin concentration, its high palatability and its antiparasitic activity even in dried or ensiled form.
Energy self-reliance, net-energy production and GHG emissions in Danish organic cash crop farms
- N. Halberg, R. Dalgaard, J.E. Olesen, T. Dalgaard
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- 25 February 2008, pp. 30-37
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Organic farming (OF) principles include the idea of reducing dependence of fossil fuels, but little has been achieved on this objective so far in Danish OF. Energy use and greenhouse gas (GHG) emissions from an average 39 ha cash crop farm were calculated and alternative crop rotations for bio-energy production were modeled. Growing rapeseed on 10% of the land could produce bio-diesel to replace 50–60% of the tractor diesel used on the farm. Increasing grass-clover area to 20% of the land and using half of this yield for biogas production could change the cash crop farm to a net energy producer, and reduce GHG emissions while reducing the overall output of products only marginally. Increasing grass-clover area would improve the nutrient management on the farm and eliminate dependence on conventional pig slurry if the biogas residues were returned to cash crop fields.
Modeling carbon cycles and estimation of greenhouse gas emissions from organic and conventional farming systems
- Björn Küstermann, Maximilian Kainz, Kurt-Jürgen Hülsbergen
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- 25 February 2008, pp. 38-52
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The paper describes the model software REPRO (REPROduction of soil fertility) designed for analyzing interlinked carbon (C) and nitrogen (N) fluxes in the system soil–plant–animal–environment. The model couples the balancing of C, N and energy fluxes with the target to estimate the climate-relevant CO2, CH4 and N2O sources and sinks of farming systems. For the determination of the net greenhouse effect, calculations of C sequestration in the soil, CO2 emissions from the use of fossil energy, CH4 emissions from livestock keeping and N2O emissions from the soil have been made. The results were converted into CO2 equivalents using its specific global warming potential (GWP). The model has been applied in the experimental farm Scheyern in southern Germany, which had been divided into an organic (org) and a conventional (con) farming system in 1992. Rather detailed series of long-term measuring data are available for the farm in Scheyern, which have been used for validating the software for its efficiency and applicability under very different management yet nearly equal site conditions.
The organic farm is multi-structured with a legume-based crop rotation (N2 fixation: 83 kg ha−1 yr−1). The livestock density (LSU=Livestock Unit according to FAO) is 1.4 LSU ha−1. The farm is oriented on closed mass cycles; from the energetic point of view it represents a low-input system (energy input 4.5 GJ ha−1 yr−1). The conventional farm is a simple-structured cash crop system, based on mineral N (N input 145 kg ha−1 yr−1). Regarding the energy consumption, the system is run on high inputs (energy input 14.0 GJ ha−1 yr−1). The organic crop rotation reaches about 57% (8.3 Mg ha−1 yr−1) of the DM yield, about 66% (163 kg ha−1 yr−1) of the N removal and roughly 56% (3741 kg ha−1 yr−1) of the C fixation of the conventional crop rotation. In the organic rotation, 18 GJ per GJ of fossil energy input are bound in the harvested biomass vis-à-vis 11.1 GJ in the conventional rotation. The strongest influence on the greenhouse effect is exerted by C sequestration and N2O emissions. In Scheyern, C sequestration has set in under organic management (+0.37 Mg ha−1 yr−1), while humus depletion has been recorded in the conventional system (−0.25 Mg ha−1 yr−1).
Greenhouse gas emissions (GGEs) due to fuel consumption and the use of machines are nearly on the same level in both crop rotations. However, the conventional system emits an additional 637 kg CO2 eq ha−1 yr−1, which had been consumed in the manufacture of mineral N and pesticides in the upstream industry.
Besides the analyses in the experimental farm Scheyern, the model has been applied in 28 commercial farms (18 org and 10 con) with comparable soil and climate conditions in the surroundings of Scheyern (mean distance 60 km). The program calculations are aimed at benchmarking the results obtained in the farming systems Scheyern; they are expected to disclose management-specific variations in the emission of climate-relevant gases and to rate the suitability of the model for describing such management-specific effects. In order to make the situation in the farms comparable, only the emissions from cropping systems were analyzed. Livestock keeping remained unconsidered. Due to lower N and energy inputs, clearly lower N2O and CO2 emissions were obtained for the organic farms than for the conventional systems.
The analyses have shown possibilities for the optimization of management and the mitigation of GGE. Our findings underline that organic farming includes a high potential for C sequestration and the reduction of GGEs. Currently, the model REPRO is tested by 90 farms in the Federal Republic of Germany with the aim to apply it in the future not only in the field of research but also in the management of commercial farms.
Financial relevance of organic farming payments for Western and Eastern European organic farms
- K. Zander, H. Nieberg, F. Offermann
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- 25 February 2008, pp. 53-61
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Organic farming in the European Union has been supported widely since 1994. Against the background of discussions concerning the design and level of organic farming support, and the relevance of organic payments for the economic success of organic farms, the question emerges as to the impact of support payments on the sustainable development of organic farming in Europe. Different databases and methodological approaches have been chosen to demonstrate the role of organic farming payments for the viability of organic farms for selected Western and Eastern European study countries. Economic analyses are based on national Farm Accountancy Data Network (FADN) in the Western European countries and on ‘typical farms’ in the Eastern European group. As a supplement to the modeling analyses, a detailed survey of 50 organic farms was carried out in each of the study countries. Organic farming payments were assessed to be ‘important’ or ‘very important’ to the economic situation on farms by the majority of the farmers surveyed. The outcome of the economic analyses shows that organic farming payments contribute on average 4–6% of gross output in the Western European countries and 4–19% in the Eastern European countries studied. The results put the level of specific support for organic farming into perspective, as other support payments and market returns contribute larger shares of total farm revenue in all the countries analyzed. Organic farming payments account for 10–30% of family farm income plus wages in Western European study countries and—after EU accession—up to three-quarters in some of the Eastern European countries, thus highlighting the considerable vulnerability of organic farms to changes in organic farming policy. As a general trend in both the West and the East, it can be observed that the policy dependency of farms has increased over recent years. Changes in organic area support, which are actually under discussion in some countries, must be carried out with a sense of proportion, since support payments will continue to play an important role in the profitability of organic farms. Nevertheless, in order to reduce dependency on area payments, organic farming support should follow an integrated approach, using a mix of support measures including, e.g., the improvement of processing and marketing facilities, support for farm cooperation and activities designed to enhance demand.
Value in the values: pasture-raised livestock products offer opportunities for reconnecting producers and consumers
- David S. Conner, Victoria Campbell-Arvai, Michael W. Hamm
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- 25 February 2008, pp. 62-69
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Pasture-based livestock production holds promise in helping to reinvigorate small and mid-scale farming, as well as farm communities, across the United States. In this study, in-depth interviews of pasture-based livestock producers, meat processors and buyers were conducted to determine behaviors, attitudes and expectations with regard to pasture-based livestock production. In addition, consumers were polled to determine their attitudes with respect to how food animals are raised and treated. Results revealed many shared values between those involved in raising, processing and distributing animal products, as well as consumers, indicating an opportunity for a ‘re-embedding’ of livestock production based on these shared values. The concurrent development of both direct and extended markets, e.g. values-based value chains, is suggested as one way of addressing the difficulties faced by individual farmers in processing and distributing animal products with their provenance and underlying values intact.
Soil property indices for assessing short-term changes in soil quality
- M.C. Bell, C.W. Raczkowski
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- 25 February 2008, pp. 70-79
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Soil quality has been proposed as a prime indicator for characterizing and defining management factors contributing to soil degradation. In this study, biological (soil respiration, fluorescent Pseudomonas bacteria and entomopathogenic nematode populations), chemical (pH, inorganic N, and total C & N), and physical (bulk density and infiltration) indicators were used to determine soil quality. The specific research objective was to determine the capacity of this specific set of indicators to assess soil quality and determine its ability to detect short-term changes in soil conditions and processes. The assessment was comparative because of the lack of specific criteria or guidelines available in the literature for interpretation of most soil property indices measured. The following treatments were chosen from an ongoing farming systems study to achieve a preplanned set of comparisons that would make this type of assessment possible: (1) best management practices/conventional tillage (BMP/CT), (2) BMP/no-tillage (BMP/NT), (3) an organic system, and (4) a successional fallow system. Assessments were made multiple times between 1999 and 2000. Statistical differences between systems were found for all soil quality indicators except for entomopathogenic nematodes. Differences between systems varied across dates, a result that supports other research stating the need to consider the temporal variability of these indices for an unbiased overall soil quality assessment. Differences in total carbon and total nitrogen between systems were most evident in the 2000 sampling dates with BMP/NT showing greater contents on the last sampling date. The soil pH and inorganic N results did not suggest a possible difference in soil function status between any of the three agricultural systems studied. All three agricultural systems, BMP/NT, BMP/CT and organic, had similar pH values and overall low soil inorganic N levels. The non-agricultural successional system had a slightly more acidic soil condition than the three agricultural systems. Soil bulk density increased with time in the untilled BMP/NT and successional systems but the resulting values were not considered detrimental to either productivity or environmental quality. Infiltration was lower in the BMP/NT and successional systems than in the BMP/CT and organic systems. In conclusion, all soil quality indicators except for entomopathogenic nematodes proved to be sensitive to the detection of rapid changes in soil conditions that occur by the influence of soil management. The importance of using soil bulk density to express soil results on a volume basis, as the soil exists in the field before sampling, prevented an average interpretation error of 7–14% as compared to treatment comparisons on a soil weight basis only. This also demonstrates the need to carefully consider field sampling locations (row, between row, or wheel traffic areas) which dramatically influence soil density, physical characteristics, organic matter concentrations, and biological activity. Failure to consider these factors can invalidate even the most careful approaches to establishing baseline soil quality levels in the field as affected by various tillage and residue management practices and associated comparisons in time.
Review Article
Integrated crop/livestock systems research: Practical research considerations
- D.L. Tanaka, J.F. Karn, E.J. Scholljegerdes
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- 25 February 2008, pp. 80-86
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There are many reasons for the paucity of integrated crop/livestock research and associated publications. Integrated/crop livestock experiments that involve adequate treatments and replications, as perceived by both crop and animal scientists, require large numbers of hectares, many animals, considerable labor to conduct the research, substantial financial resources, and a commitment by Federal and State Research Agencies to fund such long-term research projects. To be truly integrated, crop/livestock research must be multidisciplinary, involving scientists of diverse training and experience with expertise to address various aspects of the research problem, and scientists must function as a cohesive unit or team. The prevailing attitude that all experimental data must be statistically analyzed to be of any value is also a detriment to integrated research. Statistical analyses of these projects may be quite challenging and require new or unusual approaches. Related to the prevailing need for statistical analysis is also the need for scientists to publish senior authored publications for career advancement. Conducting integrated research may not facilitate scientists' publishing the number and quality of publications required for them to meet these criteria. A further obstacle to integrated research alluded to above, involves the many experimental design compromises that must be made by cooperating scientists. Crop and soil scientists for example, use many treatments and replications with small plots, while animal scientists, by necessity, have experiments that involve relatively large numbers of hectares and animal numbers with relatively few treatments and replications. It is therefore extremely difficult to initiate such projects given these inherent differences in crop versus livestock research protocol, as well as to design effective experiments that will provide publishable data. Making compromises on the many factors relevant to integrated crop/livestock research while designing experiments that will provide solutions to pertinent producer problems as well as useful data that can be statistically analyzed and published is, therefore, extremely difficult.
Book Review
Long-term Field Experiments in Organic Farming. Edited by Joachim Raupp, Carola Pekrun, Meike Oltmanns and Ulrich Köpke. 2006. International Society of Organic Agriculture Research (ISOFAR), ISOFAR Scientific Series 1, Verlag Dr Köster, Berlin, Germany. 204 p. 25 Euros, ISBN 3-89574-590-1.
- Catherine Greene
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- 25 February 2008, pp. 87-88
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