Konkurrence mellem afgrøde og ukrudt om tilført husdyrgødningskvælstof

Summary

The experiment was performed in the two spring barley fields in the organic six-course crop rotation at Foulumgaard, Denmark (56º 30’ N, 9º 35’ E). The preceding crops were a 2nd year clover-grass and cereal/beets and the weed density in the spring barley was 300 and 1800 plants/m2, respectively. Pig slurry was applied by hand in micro plots (3040 cm) by four methods: broadspreading (incorporated with good slurry-soil contact) or injected in bands to depths of 5, 10 or 15 cm (reduced slurry-soil contact). Immediately after application, the slurry was covered by at least 1-2 cm soil to prevent ammonia volatilisation.
During the tillering and elongation phase, the spring barley and weeds were sampled six times at intervals of 5-6 days. The last sampling corresponds to about ear emergence. The effect of application method on dry matter production and nitrogen uptake in the spring barley and the weeds was reported. In addition, the ammonia fraction of the pig slurry was enriched with isotopic labelled nitrogen. Thus, also the plant recovery of applied ammonia nitrogen in the pig slurry was calculated for the crop as well as the weeds.
Direct injection combined with placement of the slurry band in relation to the crop row influences the competition between crop and weed for applied nitrogen. The results show that the weed is a significant competitor for applied nitrogen when the slurry is broadspread and incorporated. Banding by direct injection reduces the slurry-soil contact and the competition balance moves in favour of the crop. Thus, the crop recovery of applied nitrogen may be increased and simultaneously the weed recovery may be reduced.