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Ukrudt i økologiske kornsædskifteforsøg

Rasmussen, Ilse A.; Askegaard, Margrethe and Olesen, Jørgen E. (1999) Ukrudt i økologiske kornsædskifteforsøg. In: 16. Danske Planteværnskonference, Plantebeskyttelse i økologisk jordbrug, Sygdomme og skadedyr. DJF-rapport, Markbrug, no. 10. Danmarks JordbrugsForskning, pp. 17-28.

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Summary

Der er igangsat forsøg med økologiske sædskifter på fire forskellige steder i Danmark, afspejlende forskellige klima- og jordbundsforhold. De fire sædskifter har forskellig andel af kvælstoffikserende afgrøder hhv. korn til modenhed, med og uden fangafgrøder og med og uden husdyrgødning. Forsøgene har været gennemført i 1997 og 1998. I forsøgene er bl.a. registreret ukrudt. Det er for tidligt at sige noget om ukrudtets udvikling i de forskellige sædskifter. Der er mest ukrudt i vintersæden begge forsøgsår alle steder. I 1997 er der i de vårsåede afgrøder mest ukrudt i byg/ært. Der er signifikant mest ukrudt i de gødede led af vinterhveden i forhold til de ugødede i Flakkebjerg 1997 og Foulum 1998. Ukrudtsbekæmpelsen har kun haft signifikant effekt på ukrudtets biomasse i vinterhveden i Foulum, hvor der i 1997 er mest ukrudt i de ubehandlede led, i 1998 er mest ukrudt i det børsterensede led, men næstmest i det ubehandlede. I Flakkebjerg var der i 1997 signifikant færrest ukrudtsplanter i havren i de ukrudtsharvede led. Der forekom i 1998 alm. kvik alle steder bortset fra i Foulum, og agertidsler i Flakkebjerg. Efter høst var der signifikant færre tidsler i parceller med efterafgrøde end uden.

Summary translation

A long-term crop rotation experiment is carried out in Denmark. The experiment focuses on possibilities for a short and a long-term increase in grain production in organic farming. The effects of different crop rotation elements on yield, nutrient leaching, weed infestation and soil nutrient availability are investigated (Olesen et al., 1998).
Four different four-year crop rotations are compared at four sites in Denmark, representing different soil types and climatic conditions. The first year of the experiment was 1997. All crops in all rotations are represented each year, but not all rotations are represented at each site. There are two replicates. Three factors are included in the experiment in a factorial design: crop rotation (fraction of grass-clover and pulses in the rotation), catch crop (without or with catch crop or by-cropped clover) and fertilizer (without or with animal manure as slurry).
The fraction of grass-clover and pulses in the rotation represents a decreasing input of nitrogen through N2-fixation. The fertilized plots are supplied with animal manure (slurry) at rates corresponding to 40% of the nitrogen demand. Weeds in cereals and pulses without undersown catch crops are controlled by weed harrowing with spring tine weeders. On the lighter soil types the wheat is sown at double normal row distance and the rows are hoed mechanically. Large perennial weed plants (i.e. creeping thistle (Cirsium arvense) or mugwort (Artemisia vulgaris)) are removed by hand weeding. Couch grass (Elymus repens) is controlled if present by repeated harrowing after harvest in plots without catch crops. If a threshold is exceeded the couch grass is also controlled in the plots with catch crops, even though this destroys the catch crop. The sugarbeets are kept weed-free by a combination of pre-emergence flaming, mechanical and manual hoeing and hand weeding of large weeds.
In the first two years of the experiment, it is not possible to draw conclusions about differences in weed flora (species, numbers and biomass) within sites pertaining to crop rotation. There was generally more weed biomass in the winter wheat than in the other crops. In 1997, there were most weeds in the pea/barley-mixture of the spring-sown crops. In the winter wheat at the lightest soil, there was more weed biomass in the unfertilized plots, but at the other locations there was more weeds (numbers and biomass) in the fertilized plots. Weed control only had significant effect in winter wheat in Foulum on biomass and oats in 1998 in Flakkebjerg on numbers.
Couch grass was found at three locations in 1998. Creeping thistle occurred at one location in 1998. After harvest it had disappeared from half of the plots where it was found during the growing season, and was almost only found in plots, where there had not the previous year been a catch crop.

EPrint Type:Report chapter
Keywords:ukrudt, korn, sædskifte,
Subjects: Crop husbandry > Production systems
Crop husbandry > Weed management
Crop husbandry > Production systems > Cereals, pulses and oilseeds
Research affiliation: Denmark > DARCOF I (1996-2001) > III Development of organic plant production systems
Deposited By: Rasmussen, Researcher Ilse A.
ID Code:245
Deposited On:25 Nov 2002
Last Modified:12 Apr 2010 07:27
Document Language:Danish - Dansk
Status:Published
Refereed:Not peer-reviewed
Additional Publishing Information:With English summary and text for figures and tables
only a pre-print version is shown

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