Weed population dynamics for contrasting organic pasture establishment techniques

Abstract

A trial was conducted on an organic dairy farm in Manawatu, New Zealand, to determine how well perennial weeds are controlled during pasture renewal. Changes in weed populations were monitored following three different non-chemical methods of regrassing. Regrassing by planting pasture 4 weeks after ploughing the old pasture ("grassto- grass") was compared for spring and autumn cultivation. The third method involved ploughing in spring, growing turnips over summer then regrassing in autumn. All three techniques caused signiicant increases in broad-leaved dock (Rumex obtusifolius) and creeping buttercup (Ranunculus repens) populations. Although both these species regrew from vegetative organs, it was the establishment of new seedlings following cultivation that appeared to increase populations most. This build-up of dock seedlings occurred more when using a crop than just grass-to-grass systems. A 2-week fallow after ploughing gave better control of perennial weeds than having no fallow, but a 4-week fallow gave little further improvement. © 2013 New Zealand Plant Protection Society.