Lars Olav Brandsæter
Senior Research Scientist
(+47) 901 09 435
lars.olav.brandsaeter@nibio.no
Place
Ås H7
Visiting address
Høgskoleveien 7, 1433 Ås
Abstract
Fast regrowth from deep roots and rhizomes makes it difficult to mechanically control the perennials Cirsium arvense and Tussilago farfara respectively. It is, however, not clear whether new shoots originate mainly from fragments of roots/rhizomes in upper soil layers or from an intact system below depth of soil cultivation. Here we present results from three experiments with natural infestations of C. arvense, and two with both C. arvense and T. farfara. Plots of 1 m2 were excavated to different depths (13–25 cm), all below-ground plant parts in the topsoil were collected and thereafter fragments were either returned to or removed from the plots. Regrowth from disturbed plots with removed or returned fragments was compared. The origin of regrown shoots, that is, whether they originated from seeds, intact below-ground root/rhizome systems or returned fragments, was examined. More C. arvense shoots originated from the intact root system (48%–84%) than from root fragments (16%–52%). The final aboveground biomass was not affected by removal of the top-soil fragments. For T. farfara, a small proportion (3%) of new shoots originated from the intact rhizome system, and the rest from fragments. We conclude that the intact root system of C. arvense contributes at least as much as root fragments to regrowth after soil cultivation, which might imply that time of treatment and depth of cultivation are crucial for the effect of mechanical control. For T. farfara, the results suggest that tillage equipment with high capacity to fragment the rhizome system will contribute to efficient control.
Authors
Marian Malte Weigel Therese With Berge Jukka Salonen Timo Lötjönen Bärbel Gerowitt Lars Olav BrandsæterAbstract
Controlling creeping perennial weeds is challenging throughout all farming systems. The present study distinguished and explored three different methods to control them non-chemically: disturbance with inversion, disturbance without inversion, and competition. Focusing on Cirsium arvense, Elymus repens, and Sonchus arvensis, we conducted a field study (2019–2021) at three northern European sites in Germany, Finland, and Norway. We investigated the effects of the control methods ploughing (inversion disturbance), root cutting (non-inversion disturbance), and cover crops (competition) alone. Root cutting was conducted using a prototype machine developed by “Kverneland”. Eight treatments were tested in factorial designs adapted for each site. Control methods were applied solely and combined. Response variables after treatments were aboveground weed biomass and grain yield of spring cereals. The control method of ploughing was most effective in reducing weed biomass compared to root cutting or cover crops. However, compared to the untreated control, a pronounced additive effect of root cutting and cover crops occurred, reducing weed biomass (−57.5%) similar to ploughing (−66%). Pooled over sites, the response was species-specific, with each species showing a distinct reaction to both control methods. C. arvense was most susceptible to root cutting, followed by E. repens, while S. arvensis showed no susceptibility. Crop yield losses were prevented compared to untreated plots by ploughing (+60.57%) and root cutting (+30%), but not by cover crops. We conclude that the combination of non-inversion disturbance and competition is a promising strategy to reduce the reliance on herbicides or inversion tillage in the management of perennial weeds.
Abstract
Elymus repens is a problematic perennial weed in annual crops, grasslands and leys. Rhizome fragmentation by vertical disking can potentially reduce E. repens abundance with minimal tillage, but data are lacking on its efficiency in forage production. In a two-year study (2017–2018, 2018–2019) conducted in two forage grass-clover leys that were mostly weed-free except for large E. repens populations, this study examined effects on forage yield, botanical composition, and E. repens rhizome biomass of rhizome fragmentation at significant growth initiation in spring (early rhizome fragmentation, ERF) and/or when conditions allowed after the first forage cut (late rhizome fragmentation, LRF). Cold, wet springs and hard, dry soil in summer delayed treatment in both treatment years, to late spring (ERF) and late summer/early autumn (LRF). In the treatment year, ERF reduced first-cut forage yield by 44% compared with no rhizome fragmentation, while LRF decreased second- and third-cut yield by 24% and 53%, respectively. In the year after treatment, ERF increased total forage yield by on average 10%, while LRF had no effect. Over both years, combined forage yield was reduced by 11% by ERF and 4% by LRF. Both treatments reduced E. repens rhizome biomass, but inconsistently (ERF by 25% in one year only, LRF by 24% at one of two sites). ERF reduced E. repens incidence in forage by 10% in the treatment year, but had no effect in the following year. Thus, rhizome fragmentation by vertical disking can reduce E. repens abundance in grass-clover leys, but the effect is inconsistent and forage yield can be impaired, especially in swards with much E. repens. Moreover, disking is hampered by hard, dry soil conditions.
