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Effects of Nitrogen Fertilization on Spotted Knapweed and Competing Vegetation in Western Montana

1989; University of Arizona; Volume: 42; Issue: 3 Linguagem: Inglês

10.2307/3899477

2162-2728

Jim M. Story, Keith W. Boggs, Donald R. Graham,

Weed Control and Herbicide Applications

The effects of N fertilization on spotted knrpweed (Cmtourccr umcuforu Lamarck) and competing vegetation were studied at 2 site-s in western Montana during 1981 through 1984.The N was applied 1 time at each site at rates of 56,112,224, and 448 kg/ha.Spotted ltnapweed biomass showed a significant, positive yield response to N at all rates at both sites during the year of applieation.The only response by spotted knapweed to N In succeeding years was in the second year at Site 1 where a significant response was detected at the 448 kg N/ha rate.Competing vegetation at Site 1 (primarily quackgrass, Agropyron repens (L.) Bauv.) in the first year showed a significant, positive response to N, while competing vegetation at Site 2 (primarily crested wheatgrass, Agropyron crisLotum (L.) Gaertu.)did not respond to N in the first year.No response by competing vegetation to N in succeeding years at either site was detected.There was a significant relationship between percent knrpweed and N rate at both sites in the year of N application, but not in succeeding years.These results suggest that N fertilization, by i&If, as a cultural control approach to knapweed may be impractical, and could contribute toward the increase of knapweed when used in some of the plant communities normally assodrtedwithspotted~pweedon~ge~dinw~~Monhna.