Papers by Erik Kristensen
Weed Research, Aug 29, 2013
Mechanical weed control of perennial weeds in organic crop production over long post-harvest peri... more Mechanical weed control of perennial weeds in organic crop production over long post-harvest periods is incompatible with the establishment of cover crops for improving soil quality and preventing nutrient leaching. We suggest a new concept that comprises uprooting and immediate removal of vegetative propagules located within the plough layer to allow for quick re-establishment of a plant cover. A field experiment comparing the effects of conventional practices (stubble cultivation) with different combinations of rotary cultivation (One, Two or four passes) and cover crops (none vs. rye-vetch-mustard mixture) on Elytrigia repens rhizome removal, shoot growth and suppression of a subsequent barley crop was examined in two growing seasons. Four passes with a modified rotary cultivator, where each pass was followed by rhizome removal, reduced E. repens shoot growth in barley by 84% and 97%. In general, the cover crop developed poorly and did not affect barley or E. repens. Barley yield was only affected by treatments in the first season, where yield was negatively correlated with E. repens shoot biomass. The concept has potential for the control of severe E. repens infestations, but future research aimed at identifying more effective smother crops and less intensive methods of rhizome removal is needed.
European Biomass Conference and Exhibition Proceedings, 2019
Straw combustion generates a high concentration of particle emission. Particulate matter in ambie... more Straw combustion generates a high concentration of particle emission. Particulate matter in ambient air is associated with health problems. Therefore, there is a need for a filter technology to clean the flue gas and achieve an effective reduction of dust emission from biomass boilers. The aim of this work has been to develop and optimize electrostatic precipitators for small biomass boilers. Focus has been on a filter connected to a 150 kW manually stoked batch straw boiler. In order to ensure low emissions, a high flexibility of the ESP is required, ie. an accurate regulated ratio between the heating time of the ESP and the boiler operation must be guaranteed inclusive operation at partial load and especially during start-up. Control automation as well as effective mechanical systems for removing dust deposits on discharge electrodes and plate collectors have been developed and tested. For a set-up with the 150 kW manual batch stoked straw boiler results show a filter efficiency of about 95 percent. The PM in the cleaned flue gas is 6-16 mg Nm-3. The technology will contribute to increase the use of biomass and help in reducing in overall CO2 emissions by substitution of fossil energy with renewable biomass.
International Conference on Agricultural Engineering - AgEng 2010: towards environmental technologies, Clermont-Ferrand, France, 6-8 September 2010., Sep 6, 2010
Elymus repens (coach grass) is traditionally controlled by repeated and prolonged stubble cultiva... more Elymus repens (coach grass) is traditionally controlled by repeated and prolonged stubble cultivation. However, the efficacy is strongly depending on weather and secondly on the exposure of rhizomes. The shorter the required period of cultivation stays the more compliance with the objective in organic farming where farmers aim at minimizing leaching of nutrients by keeping the soil plant-covered during autumn and winter. Effective technique and strategies for uprooting, exposing and destroying Elymus repens are needed. In a Danish organic research project the focus is on technological solutions for uprooting, exposing and destroying of the rhizomes within a short time span. Machines of standard type, modified machines and machines constructed for other purposes have been studied. The results show that it is difficult to achieve a high percentage of uprooting when using machines giving a high area capacity, e.g. spring loaded tine cultivator and rigid tine cultivator with modified spike discs at the rear.
European Biomass Conference and Exhibition Proceedings, 2016
Small straw and wood fired boilers may be a significant source of air pollution as the combustion... more Small straw and wood fired boilers may be a significant source of air pollution as the combustion generates a high amount of particle emission in the flue gas. This paper describes flue gas cleaning by electrostatic precipitators developed for small wood and straw boilers with heating capacity from 4kW up to 500kW. Fulfilling the European standard EN 303-5 for small boilers demands a cleaning system for the flue gas. Especially for straw fired boilers the challenges are high. There are no suitable filters in the market. Cleaning by means of cyclones is insufficient, fabric filters are not suitable and traditional precipitator technology does not work. Different filter sizes and types for the actual boiler size and biomass types (straw, wood chips and wood pellets) have been developed and tested. Control automation as well as effective mechanical systems for removing dust deposits from the discharge electrodes and the colleting plats has been developed and tested. Total collection efficiency of 95-99 % has been achieved. The project is collaboration between two commercial companies and a university.
Biosystems Engineering, Oct 1, 2005
Mycotoxin producing fungi are naturally occurring components in cereals. When produced, some of t... more Mycotoxin producing fungi are naturally occurring components in cereals. When produced, some of the mycotoxins are toxic to humans and animals. Heat treatment is a method to reduce fungal abundance on cereals. The objectives of this work have been to provide more knowledge on this topic, and specifically to optimise the drum drying technique with reference to reducing the dissemination and proliferation of fungi on organically grown rye without reducing the baking quality of the grain. The results show that drum drying can be a very efficient method in reducing fungi colonising on grain. For rye it is possible to achieve high effects on fungi without reducing the baking abilities. When drying at a constant maximum grain temperature of 64°C, the treatment resulted in less than 1% of the yeast propagules and less than 2% of the filamentous fungi, compared to what was found in the reference grain. As drying temperatures and time for the grain to be treated are essential, the drum drier must be equipped with an effective control unit. The experiments show that a control system using fixed constant maximum grain temperature is most suitable.
Introduktion Bekaempelse af ukrudt i raekkeafgrøder er vanskeligt i selve raekken-mellem raekkern... more Introduktion Bekaempelse af ukrudt i raekkeafgrøder er vanskeligt i selve raekken-mellem raekkerne kan radrensning klare problemet. Ved at dampe jorden inden såning kan man fjerne eller i hvert fald mindske problemet, simpelthen ved at udsaette kimplanter og ukrudtsfrø for så staerk varme, at de ødelaegges.
... Uffe Jørgensen, Department of Crop Physiology and Soil Science Tommy Dalgaard Department of A... more ... Uffe Jørgensen, Department of Crop Physiology and Soil Science Tommy Dalgaard Department of Agricultural Systems ... Can be established without weed treatment lower yield Annual N-fixing of 30 185 kg N/ha Frost hardy and resistant to pests Page 12. DIAS ...
Vedrørende "Notat om god praksis for høst af brødkorn under vanskelige forhold" Naervaerende nota... more Vedrørende "Notat om god praksis for høst af brødkorn under vanskelige forhold" Naervaerende notat er udarbejdet som led i "Aftale mellem Aarhus Universitet og Fødevareministeriet om udførelse af forskningsbaseret myndighedsbetjening m.v. på Det Jordbrugsvidenskabelige Fakultet 2011-2014" (Punkt 4.7 i aftalens Bilag 2). Notatet er udarbejdet af lektor Johannes Ravn Jørgensen, Institut for Agroøkologi, akademisk medarbejder Erik Fløjgaard Kristensen, Institut for Ingeniørvidenskab, seniorforsker Susanne Elmholt, DCA-Nationalt Center for Fødevarer og Jordbrug og seniorforsker Finn Pilgaard Vinther, Institut for Agroøkologi.
Temperatur og fugtighed i korn og frø skal kendes for at sikre optimal styring af et tørringsanla... more Temperatur og fugtighed i korn og frø skal kendes for at sikre optimal styring af et tørringsanlaeg og for at kontrollere, at lagringen sker uden kvalitetsforringelse. Resultaterne har vist, at trådløse sensorbolde kan anvendes til sikker måling af temperatur og fugtighed via måling af den relative luftfugtighed. På grundlag af det kendte ligevaegtsforhold mellem vandindhold i korn og frø og den omgivende lufts relative fugtighed og temperatur omregnes måleresultatet for de traditionelle kornarter og en raekke frøarter til afgrødens vandprocent. Måleresultaterne vedrørende vandprocent kan kun anvendes, når der ikke blaeses i afgrøden. For at opnå brugbare resultater kraeves minimum 3 timers stilstand. En temperaturstigning i et parti korn eller frø skyldes ofte nedbrydning af varen og vaekst af skadelige svampe. Hvis temperaturen eller fugtigheden stiger, registreres det via sensorboldene. Måleresultaterne kan direkte anvendes til at styre den nødvendige tørring og køling af afgrøden. Registreringerne vil ligeledes kunne anvendes til at dokumentere lagringsbetingelserne, eksempelvis ved krav om sporbarhed. Der er i forsøgene anvendt et totrins datatransmission setup , hvor en raekke sensorer enten direkte eller gennem en nabosensor sender data til en basestation, hvorfra data trådløst videresendes til en internetserver, således at resultaterne kan ses på brugerens computer. Systemet har fungeret uden problemer. Trådløse sensorbolde kan således vaere et godt alternativ til traditionelle systemer med faste målesensorer placeret i lageret og forbundet med kabler til en kontrolboks.
2006 Portland, Oregon, July 9-12, 2006, 2006
ABSTRACT authors are solely responsible for the content of this technical presentation. The techn... more ABSTRACT authors are solely responsible for the content of this technical presentation. The technical presentation does not necessarily reflect the official position of the American Society of Agricultural and Biological Engineers (ASABE), and its printing and distribution does not constitute an endorsement of views which may be expressed. Technical presentations are not subject to the formal peer review process by ASABE editorial committees; therefore, they are not to be presented as refereed publications. Citation of this work should state that it is from an ASABE meeting paper. EXAMPLE: Author Abstract. : Ridge tillage may improve organic row crop production in terms of higher yields and lower impacts on the environment. Ridge tillage is hardly ever used in Europe. In Denmark, growing of row crops in a ridge tillage system has been tested. In particular, organic grown maize has shown very promising results. In some of the test plots, yields increased with up to 50 percent as compared with conventional flat seedbeds. On average, year 2005 results for organic maize grown on sandy soil showed increased yields of about 20 percent. Prior to putting the ridge tillage method into practice, a number of technical questions have to be solved. The project presented in this paper takes focus on these technical matters. Especially, the establishment of a uniform ridge at varying soil types and conditions is important. The goal is to develop a machine able to ridge up the soil, perform precision drilling and make a seedbed with optimal germinating conditions for the seeds. Another important practical aspect is the machine capacity and operational performance. In the ongoing project, a four rowed machine for putting up the ridge and sowing in one operation have been constructed and tested. This machine has a width of 3 m and a working speed of 4 km per hour resulting in a labour requirement of 1.23 h ha -1 and a field capacity of 0.90 ha h -1 . In practice, a machine with a width of 6 m and a speed of 5 km per hour
ABSTRACT ISBN 978 974 8257 70 9
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Papers by Erik Kristensen