Development of weeds in organic crop rotation experiments

Weeds are a major problem in organic farming. Preventive as well as curative measures must be utilised to manage the weeds and avoid proliferation. Besides direct weed control measures, many different aspects of planning and management in the cropping system affect the proliferation of weeds. However, it has rarely been investigated how the whole system affects weed populations

Organic farming effects on clay dispersion in carbon-exhausted soils

Many Danish soils are depleted in organic matter (OM) after decades of intensive cereal cultivation (Schjønning et al., 2009). In this paper we show that clay particles (colloids) in soils that are low in OM content are easily dispersed in the soil water, which in turn has important effects on soil ecosystem functions and services. Organic farming systems generally tend to increase soil OM contents and may thus mitigate the negative effects

Improved weed management in organic crop production

Weed problems can constrain organic crop production resulting in significant losses in yield and quality. Especially perennial weed species such as Elytrigia repens, Cirsium arvense and Tussilago farfara are posing problems as arable cropping systems do not hamper their vegetative proliferation sufficiently. Annual weeds may also reach unacceptable infestation levels leaving the growers with poor yielding crops and severe future weed problems owing to the shedding and spread of weed seeds. Effective weed management is a key component for successful organic crop production and a prerequisite to increase the yielding potential of many organic crop production systems. Weed problems are most severe on stockless arable farms because the supply of nutrients can be limited and may not suffice to produce competitive crop stands. Crop rotations in arable cropping systems often have fewer grass-clovers leys or other perennial crops known to disrupt weed proliferation more effectively than cash crops such as cereals and pulses. The higher nutritional status of soils on dairy farms and the more frequent use of perennial crops for mowing are major causes for less severe weed problems on those farms

Barriers for developing more robust organic arable farming systems in practice

There is a gap between the scientific idea of robust and economically viable organic arable farming systems with optimized crop rotations for nutrient and pest management and how these systems look like in practice. In order to explore this gap, we visited and interviewed ten organic arable farms in Denmark. Our main findings are: 1) Organic arable farming operates in a very dynamic and changing environment in terms of prizing and market opportunities, and the main focus of the farm managements was the coping strategy within this changing environment; 2) The farming systems were continuously changing and developing, buying and renting more land, changing manure agreements and other forms of cooperation and arrangements; 3) Short term profit was paid much more attention than more theoretical expectation on long term profit or opportunities in relation to optimizing the production system. This again seems logical in relation to the very dynamic world that the farmers have to operate within; 4) Most of the farmers do not see their farm as a coherent system but as a coordination of a series of separate operations, which means that most decisions are taken with specific reference to the individual field in at the present situation without considering the long-term effects. Management focus is thus much more on solving problems as they are occurring, by adjusting their practice, than it is on developing a robust system preventing problems to occur. This partial focus is also strongly supported by the way in which extension services mostly operate

Searching the critical soil organic carbon threshold for satisfactory tilth conditions – test of the Dexter clay:carbon hypothesis

The concern for deteriorating soil structure at low soil organic matter (SOM) contents calls for better knowledge of SOM interaction with soil minerals as well as guidelines for soil conservation. We measured clay dispersibility in a field with a textural gradient. Our results support the concept of differentiating soil content of clay in a complexed and non-complexed part although our data did not point out an exact clay/OC ratio threshold. Our results also indicated that labile fractions of SOM may play an important role in soil physical behavior. We revisited literature data and found evidence that soil content of fines (<2 or <20 μm) is a major determinant of soil specific surface area (SA). We noted that soil SA coverage with SOM changed dramatically at a specific ratio of either clay (<2 μm) or clay+silt (<20 μm) with soil OC. This is an indirect support of the recently suggested quantification of the soil mineral ‘saturation’ hypothesis. More studies are needed on the causal relationships. We conclude that clay/OC~10 or (clay+silt20μm)/OC~20 are corresponding indices reflecting shift in soil physical behavior

Økologiske sædskifter til korn - kan produktionen øges?

Hvordan kan sædskiftet indrettes så den økologiske kornproduktion øges uden at bæredygtigheden mindskes? Dette centrale spørgsmål belyses med nye resultater fra det økologiske sædskifteforsøg, der i 1996/97 blev anlagt på tre lokaliteter i Danmark og som nu har kørt to rotationer

Can on-farm bioenergy production make organic farming more sustainable? - A model for energy balance, nitrogen losses, and green house gas emissions in a 1000 ha energy catchment with organic dairy farming and integrated bioenergy production

Can biogas and bioethanol production make organic farming more sustainable? - Results from a model for the fossil energy balance, Nitrogen losses, and greenhouse gas emissions in a 1000 ha energy catchment with organic dairy farming and integrated biogas and bioethanol production. Dalgaard T1, Pugesgaard S1, Jørgensen U1, Olesen JE1, Møller HB1 and Jensen ES2 1) Dept. Agroecology and Environment. Faculty of Agricultural Sciences (DJF), University of Aarhus. DK-8830 Tjele. Denmark. Contact: [email protected] 2) Biosystems Department, Risø DTU, The National Laboratory for Sustainable Energy, The Technical University of Denmark DK-4000 Roskilde, Denmark The vision of organic farming systems, independent of fossil energy resources, with significantly lower nutrient losses, and no net contribution to the greenhouse gas emissions might be fulfilled via the integration of biogas production. This is an important hypothesis investigated in the www.bioconcens.elr.dk/uk/ research project. This poster illustrates preliminary results from a model for the fossil energy balance, Nitrogen losses, and greenhouse gas emissions in a 1000 ha energy catchment with organic dairy farming and integrated biogas production in Denmark. The model will draw on results from previous models (e.g the farmGHG model), and includes a number of organic dairy farm type components, including information on livestock production, housing, manure storage, manure and fodder import/export, crop rotations, yield levels, and soil types. In addition, a biogas plant model component evaluates effects of the inclusion of variable amounts of manures and crop residues from the specified farm types, into the biogas energy production. The model is intended to result in an overall catchment balance for the following three types of indicators: 1) the fossil energy use – i.e. the net fossil energy use minus the bioenergy production, 2) losses of Nitrogen in the form of nitrates, ammonia and nitrous oxide, and 3) the emission of the three main greenhouse gasses from agriculture: carbon dioxide, nitrous oxide and methane, measured in carbon dioxide equivalents. Moreover, these indicator values are specified for each of the farm types included in the model, and for the biogas plant component. Finally, selected model results are discussed in relation to the overall hypothesis of the research project, and it is discussed how the integration of biogas production in organic farming, can help to improve the self-sufficiency in Nitrogen, and thereby reduce the import of nutrients to the organic farming systems

Management of perennial weeds and nitrogen leaching in arable cropping systems

A crop rotation experiment was established in 1997 at three locations representing different soil types and climates. Three factors were tested: crop rotation, catch crop and manure. Catch crop reduced nitrate leaching, but prohibited stubble cultivation. The use of catch crops resulted in increased levels of perennial weeds (E. repens) at one location, while at another; the level of C. arvense was not affected by catch crops, when compared with the use of stubble cultivation. Management of perennial weeds should include considerations of where in a crop rotation to use stubble cultivation, and this should preferably not be after a pulse crop. Catch crops are a more profitable way to manage C. arvense than stubble cultivations

HighCrop

Højere produktivet i dansk økologisk planteproduktio

Nitratudvaskning fra økologiske og konventionelle planteavlsbedrifter - simuleringer med FASSET bedriftsmodellen

Med udgangspunkt i regnskabsdata fra Fødevareøkonomisk Institut (FØI) og data fra Centrale Registre (CR) blev importen af kvælstof (N) i gødning til marken til konventionelle og økologiske planteavlere estimeret til hhv. 129 og 51 kg N ha-1 år-1. Desuden blev der med udgangspunkt i den aktuelle afgrødefordeling opstillet et generelt sædskifte for hver af de to systemer. Det opstillede sædskifte for den økologiske planteavl havde en høj andel af vårsæd og desuden 20% kløvergræs, mens den konventionelle planteavl var domineret af kornafgrøder primært i form af vintersæd. Med baggrund i disse model-sædskifter blev N-balancen på markniveau beregnet ved anvendelse af FASSET modellen. Dette inkluderede også N-udvaskning og ændring i jordens N-pulje. Alle beregninger blev foretaget for tre jordtyper, der repræsenterer variationen i danske jordtyper. Disse tre jordtyper blev ydermere delt op i lav og høj frugtbarhed, repræsenteret ved et lavt og højt indhold af organisk N i jorden. Modelresultaterne viste, at den økologiske planteavl havde en højere markbalance end den konventionelle planteavl (61 mod 40 kg N ha-1 år-1). Men da indbygningen i jordens N-pulje samtidig var højere for de økologiske brug, gav dette ikke anledning til forskelle i niveauet for udvaskning. De økologiske bedrifter øgede deres jordfrugtbarhed ved årligt i gennemsnit at indbygge 13 kg N ha-1 i jorden, mens de konventionelle reducerede frugtbarheden ved i gennemsnit at tære 6 kg N ha-1 år-1 på jordens indhold af organisk N. Dette kan primært tillægges forskelle i afgrødevalg. Desuden blev en række driftsmæssige tiltag analyseret, herunder efterafgrøder, halmnedmuldning, reduceret gødningstilførsel og ændringer i sædskiftet. Disse analyser viste, at etablering af efterafgrøder er det klart mest effektive virkemiddel til at reducere N-udvaskningen, med en effekt på sædskifteniveau på ca. 9 kg N ha-1 år-1. Det fulde potentiale ved dyrkning af efterafgrøder vil dog ikke kunne udnyttes i praksis, da der af hensyn til bekæmpelse af især rodukrudt, er nødvendigt med en jordbearbejdning i efteråret, der kan give anledning til en betydelig øget N-udvaskning. Andre tiltag, som f.eks. halmnedmuldning, havde mindre effekt på N-udvaskningen, men en markant effekt på jordens indhold af organisk N. Således øgede halmnedmuldningen ved den økologiske planteavl jordens indhold af organisk N med 14 kg N ha-1 år-1 mere end i basis-scenariet. På basis af simuleringerne blev det konkluderet at der ikke er nogen forskel i udvaskningsniveauet mellem økologisk og konventionel planteavl. Da N-udvaskningen fra konventionel planteavl blev simuleret at være faldet 4 kg N ha-1 år-1 som følge af implementeringen af VMP II blev det vurderet, at der har været ca. 4 kg N ha-1 år-1 mere N-udvaskning fra konventionel planteproduktion i forhold til niveauet for økologisk planteavl før VMP II