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 nonchemical 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 significant increases in broadleaved 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 buildup of dock seedlings occurred more when using a crop than just grasstograss systems A 2week fallow after ploughing gave better control of perennial weeds than having no fallow but a 4week fallow gave little further improvement

Can differences in <i>Cirsium arvense</i> and <i>Rumex obtusifolius</i> densities within pastures be explained by soil parameters

“…Earlier work on this farm showed that the soil has large numbers of broad-leaved dock seeds that germinate readily when the soil is free of competition during establishment of new pastures (Harrington et al 2013). Given that the soil parameters measured did not assist with explaining why dock plants were at higher densities in some areas than others, a logical explanation is probably that the species had established whenever the pasture cover has been disturbed sufficiently in the past to allow seeds to germinate and establish successfully.…”

“…Their presence can probably be more logically explained by disturbance of the patches in the past that have allowed seedlings to establish. Or perhaps the establishment of these perennial species in the various patches dated back to when the pastures were first sown, at which time perennial weeds can establish readily (Harrington et al 2013).…”

Effects of renewal time, taproot cutting, ploughing practice, false seedbed and companion crop on docks (Rumex spp.) when renewing grassland

“…A major aspect of grassland management is grassland renewal; representing both a great opportunity and great risk to dock management (Harrington et al, 2013). Grassland renewal is generally performed by re-sowing after ploughing.…”

“…While ploughing can bury seeds deeper in the soil where they will not germinate, it can also bring up seeds to the surface. Moreover, only a brief exposure to light is needed for dock seeds to germinate, therefore soil disturbance can result in a large increase in germinating dock seeds (Pye and Andersson, 2009;Harrington et al, 2013). Thus, the challenge lies in finding techniques that are potent enough to destroy the established dock plants, without using too many resources, and without allowing re-establishment from root or seed.…”

Weed Management in New Zealand Pastures

“…Consumer preferences for food produced without pesticides or minimal pesticides have created market forces that encourage a move to farming systems that use less or no herbicides. Research in New Zealand has shown that in the absence of herbicides on organic dairy farms, high pasture production can still be achieved by managing weeds using pasture and grazing management [118][119][120]. However, within such systems, there needs to be more tolerance by farmers of low weed densities within pastures, many of which are eaten by livestock and have some benefits [121].…”