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Couch grass studies: 1. reaction on burial depth and nitrogen availability and placement in competition with a crop : 2. reduced use of glyfosat on fallow

Forsberg, Sam


In this trial it was investigated how couch grass (Elymus repens) changes its ability to compete in stands ofwheat and barley with different burial depth and different amounts and placement of nitrogen. More knowledge in this area can be valuable in the attempt to decrease the use of herbicides and still keep the weeds under control. The trial was carried out in the summer of 2004 as an outdoor pot experiment. The pots contained 15 litres of soil with a surface of 0,06 m2 . Couch grass was planted at two different depths, 2 cm and 6 cm under the soil surface. At the same time tree different stands of cereals were established in the pots. Spring wheat was planted with 12 or 36 kernels in each pot or spring barley with 28 kernels in each poL The cereals were seeded at a depth of 2 cm. The different stands of cereals and couch grass were grown at two different levels of nitrogen supplay, a high level, corresponding to 150 kg/ha N, and a low level, corresponding to 40 kg/ha N. The nitrogen was supplied in fonn of calcium nitrate and was either placed 3-5 cm or 7-9 cm under the soil surface. Af ter harvest the plant material was dried, and the biomass measured by weight. Both for couch grass and cereals the biomass produced above ground was measured. For couch grass the biomass of the underground plant parts (horizontal rhizomes and vertical shoot bases) were also measured. The results indicated that couch grass was favoured by a high availability of nitrogen. When the supplied amount of nitrogen increased from about 40 kg/ha to about 150 kg/ha, the biomass production of couch grass increased propOliionally as much as it did for barley and more than it did for wheat. This means that the high er level of nitrogen did not favour the cereals in their competition with couch grass. The results also suggest that couch grass was favoured when nitrogen was placed c10ser to the planted rhizomes. Thus, when couch grass was planted at a depth of2 cm and nitrogen (150 kg/ha N) 5-7 cm below the planting depth, the biomass production was about 20 % lower than when the nitrogen was placed 1-3 cm below the planting depth. The difference between the two nitrogen placements was small er at the lower nitrogen level than at the higher. The biomass production of wheat and barley was not measurably affected by the placement of nitrogen. Couch grass planted at the 6-cm depth produced almost the same amount ofbiomass either the nitrogen was placed 1-3 cm above or 1-3 cm below the planting depth. But the result may have been affected by heavy rainfall during a period shOlily after planting. Most nitrogen was added as nitrate which is easily transpOlied downwards in the soil. At the higher nitrogen level couch grass planted at a depth of 6 cm produced 20 % less biomass than couch grass planted at a depth of 2 cm. The difference between the two nitrogen placements was small er at the lower nitrogen level. The result also indicated that spring wheat, when compared to barley and couch grass, was a stronger competitor at the lower nitrogen availability than at the higher


jordbearbetning; kvickrot; konkurrenskraft; planteringsdjup; kvävetillgång; myllningsdjup; reducerad glyfosatanvändning; trädad åkermark

Published in

Meddelanden från Jordbearbetningsavdelningen
2005, number: 49
Publisher: Institutionen för markvetenskap, Avdelningen för jordbearbetning

      SLU Authors

    • Forsberg, Sam

      • Department of Soil Sciences, Swedish University of Agricultural Sciences

    UKÄ Subject classification

    Agricultural Science

    Permanent link to this page (URI)