ERA-NET SusCrop ACDC - Applying and Combining Disturbance and Competition for an agro-ecological management of creeping perennial weeds

The project "AC/DC-weeds" aims to develop sustainable weed control methods leading to reduced need of intensive soil tillage and glyphosate to control creeping perennial weeds such as couch grass (Elymus repens), perennial sow-thistle (Sonchus arvensis) and creeping thistle (Cirsium arvense). New methods for sustainable control of creeping perennial weeds in agriculture require combining both preventive and direct control measures. Field and growth chamber experiments, method development, literature studies and modelling were conducted in cooperation between NMBU, NIBIO, LUKE (FI), University of Copenhagen (DK), INRAE (FR) and the project coordinator Rostock University (DE). NMBU coordinated work package (WP) Disturbance. A comprehensive joint multi-year field trial (Germany, Finland, Norway) was performed in spring cereals. The experiment included three factors (each with two levels: with and without): Subsidiary crops (in Norway: ryegrass + clover), Kverneland root cutter (a below-ground horizontal cutter that gives minimal soil disturbance), and mouldboard ploughing in spring. Other promising tools such as the Kvick-Finn harrow, alone or in combination with root cutting or glyphosate, were also included as additional treatments at two of the sites. For creeping thistle in Norway, root cutting gave very good (86% reduction) and about the same effect as ploughing (89%). Ploughing also reduced coach grass significantly (82%), while the relatively strong reduction by root cutting was not significant. The combination of root cutting and ploughing, reduced the perennial sow-thistle by 78% from 2020 to 2021. Among the three tested factors, ploughing gave the best weed control, followed by root cutting and subsidiary crops with least effect. Our results show that root cutting has the potential to control creeping thistle to similar level as ploughing. To control couch grass and perennial sow-thistle, root cutting can be an alternative to traditional mechanical stubble harrowing. The results confirm the possibility of combining root cutting and subsidiary crops, and that it preferably can be combined with Kvick-Finn harrow in spring. NIBIO was responsible for WP Species which included studying weak time points, revealing knowledge gaps on the biology of the three weed species, and special experiments for couch grass, perennial sow-thistle and creeping thistle. For couch grass, one joint experiment was performed (Finland and Norway) and results showed that mowing and pelargonic acid needed to be combined with enhanced crop competition to be effective. For perennial sow-thistle, a joint outdoor pot experiment was done (Germany, Finland and Norway) with cutting the above ground plant parts at four different times, as well as two field experiments (Norway) with mowing, root cutting or harrowing at two times in the autumn, i.e. before and after the perennial sow-thistle roots entered the dormant period. Early measures tended to give less sow-thistle the subsequent year than late measures. Students in Norway and Germany contributed in the experiments on perennial sow-thistle and creeping thistle. These species have different biological and ecological characteristics and we reviewed and systematized published and other literature on biology, ecology and the effect of competition and disturbance of above-ground and below-ground plant parts of the weeds. In WP Monitoring, led by Copenhagen University, NIBIO/NMBU sampled drone images above the field trials in Norway. During 2019-2021, images were taken in seven trials. The RGB drone images were acquired at the same time as manual field assessments and ground-based images were collected. Since creeping perennials spread by sprouting from the creeping roots or rhizomes, creeping perennials often appear in patches. The goal is machine vision algorithms to detect and map distribution of creeping perennials in cereal fields. Such algorithms are crucial both as research tools in weed research and as part of integrated site-specific weed control. In several work packages of the project, literature studies were conducted. This was used to study the effect of competition on creeping perennials and this knowledge will be systematized in a meta-analysis (led by INRAE in France). A qualitative model for effect of weeding measures and factors (INRAE) was created, and two animation films about creeping thistle and perennial sow-thistle, resp., were made (Rostock University). Films have English sound, and sub-titles in Norwegian, Finnish, French and German. Knowledge from the project is communicated to advisors, farmers and other stakeholders.

Prosjektet har studert nye metoder for ugrasbekjempelse både for å redusere behovet for intensiv jordarbeiding, og bruken av ugrasmiddelet glyfosat. I utviklingen av nye metoder for bærekraftig kontroll av rotugras i landbruket er det et ønske at forebyggende tiltak, f.eks. fangvekster som konkurrerer med ugraset, har en mest mulig sentral rolle og at det suppleres/kombineres med direktetiltak, eksempelvis stubbharving eller sprøyting, ved behov. Tilfredsstillende avlingsnivå og ugraskontroll er selvfølgelig sentrale krav til metodene. Andre viktige elementer i bærekraftige dyrking er så lite klimaavtrykk som mulig og velfungerende økosystemtjenester som hindrer erosjon og utvasking av matjorda og ivaretar biologisk mangfold. Vi tror at våre forsøk, og kunnskapen fra dette prosjektet, i stor grad sammenfaller med målsetningene beskrevet over., i alle fall gir viktige bidrag. I prosjektet har vi studert nye bekjempelsesmetoder som har potensiale til å ivareta mange sentrale økosystemtjenester. I forhold til ulike målgrupper/brukere tror vi dette prosjektet eksempelvis kan ha følgende betydning: 1. Gjennom aktive formidling i prosjektet med fagmøter og feltdager har vi overført kunnskap til mange gårdbrukere. Vi tror at flere elementer av våre bekjempelsesmetoder vil tas i bruk i praksis. 2. Gjennom vitenskapelig publisering på kongresser og i journaler er kunnskap fra prosjektet spredt i akademia, vi tror mange vil ha stor interesse for dette. Dette har også betydning i forhold til nettverksbygging og internasjonalt forskningssamarbeid. Dette vil ytterligere forsterkes når vi har ferdigpublisert alle artikler. 3. Resultatene fra prosjektet vil ha betydning for næringslivet, for eksempel for kommersialisering av prototyper vi har brukt i forsøkene. 4. Kunnskap fra prosjektet er også relevant i forvaltning av landbruksareal, f.eks. knyttet til jordarbeiding og forskrift om regionale miljøtilskudd. 5. Kunnskap fra prosjektet vil vi bruke i nye prosjekt, f.eks. det nye prosjektet «SUSWECO - Sustainable weed control in cereals by combining subsidiary crops and minimal soil disturbance» (2023-2026).

The objective of AC/DC-weeds is to implement more and better agro-ecological management for creeping perennials in arable farming. Overall aim is to reduce plough-tillage in organic and conventional farming – and to replace glyphosate use in the latter also. Novel approaches for agro-ecological management of perennial weeds demand to exploit, combine and evaluate cultural and physical control and bio-based herbicides. Creeping perennials are suppressed by disturbance or through competition hence, an agro-ecological management must activate these processes in a suitable and rational way. New ways of applying disturbance subterranean without turning the soil will be examined in joint field experiments together with defoliation strategies via cutting or biocompatible herbicides. The effects of enhanced competition on creeping perennials will be systematized in a meta-analysis. The excerpting knowledge will feed a trait-based joint database. Specific data for Elymus repens, Cirsium arvense and Sonchus arvense will be pooled, knowledge gaps identified and close through specific semi-field experiments. Due to their clonal life-style resulting in patches monitoring whole fields is vital for perennials. We follow new approaches to spatially explicit monitor perennials with available technical tools like cameras or sensor installed in drones or vehicles. Reliable algorithms will be developed to monitor perennials. Qualitative models to analyse the impact of cropping practices, soil, weather and field environment on perennial infestations will be designed. With the help of a novel interactive graphical web tool spatial visualization for different scenarios of applying disturbance and competition will be developed. Communication and dissemination will target advisors and farmers in conventional and organic farming and other stakeholder like land owner and nature conservation.