There are 9 metadata records describing the research data generated during the investment “Improving weed management in high break crop intensity farming systems”. Each record has a numbered Dataset in the title.

Experimental data was collected from trials where IMI herbicides were applied in the break crop phase or cereal phase of a farming system, at different frequencies in the crop rotation, and measured the carryover effect on the following cereal or break crops with respect to impact on broadleaf weeds.

A canola-wheat-barley-lentil system-based trial was established at the Hart field site (Mid-North, South Australia) in 2017. Vetch/tares and bedstraw seeds were sown in 2017 to build up the weed population at the trial site, with treatments initiated from 2018.

Another lentil-wheat-lentil-wheat system-based trial was established in 2018 in Bute (Yorke Peninsula, South Australia) having a background population of bifora.

The trials were sown by using a no-till plot seeder fitted with knife-point tines and press wheels. Plots were 10 m long and contained 12 crop rows spaced 22.5 cm apart. The experiments were laid out in a split plot design at Hart and split-split plot design at Bute with four replications.

Sowing was done with the first break of the season in moist conditions at Hart on June 5, 2018 and May 30, 2019, and at Bute on June 19, 2018 and May 8, 2019. Wheat (variety Clearfield^® Chief), barley (variety Clearfield^® Spartacus) and lentil (variety PBA Hurricane XT) were sown at a depth of 4-5 cm for a target of 200, 150 and 120 plants m^-2, respectively, whereas canola (variety Clearfield^® canola 44Y90) sown at a depth of 2-3 cm for a target of 45 plants m^-2.

Fertilizer rate was consistent with the local grower practice of 80 kg ha^-1 of monoammonium phosphate (10 kg N ha^-1 and 20 kg P ha^-1) in lentil, and 80 kg ha^-1 of diammonium phosphate (18 kg N ha^-1 and 20 kg P ha^-1) in cereals and canola banded below the seed at sowing. A pre-seeding application of glyphosate at 1200 g ha^-1 and carfentrazone at 30 g ha^-1 was made to control existing weeds in the field.

Herbicide treatments included combinations of non-IMI and IMI herbicides applied in combination and rotation in different years as summarised below:

Herbicides used at Hart in 2018 and 2019:

• Canola: Lontrel (Group 4) post sowing (POST) ± OnDuty (Group 2) POST
• Wheat: Eclipse (Group 2) POST + LVE MCPA (Group 4) POST + Clopyralid (Group 4) POST ± OnDuty (Group 2) POST
• Barley: Bromoxynil + Dicamba (Group 5 and 4) POST ± Imazamox + imazapyr (Group 2) POST
• Lentil: Metribuzin (Group 5) post sowing, post emergence (PSPE) + Broadstrike (Group 2) or Imazamox + imazapyr (Group 2) POST

Herbicides used at Bute in 2018:

• Wheat: {MCPA Amine (4) POST + Affinity (14) POST} ± {Paradigm (4 + 2) + LVE-MCPA (4)} ± OnDuty (2) POST
• Lentil: Metribuzin (5) PSPE + Broadstrike (2) or Imazamox + imazapyr (2) POST ± chlorsulfuron incorporated by sowing (IBS)

Herbicides used at Bute in 2019:

• Wheat: {MCPA Amine (4) POST + Affinity (14) POST} ± chlorsulfuron ± OnDuty (2) POST
• Lentil: Metribuzin (5) PSPE + Broadstrike (2) or Imazamox + imazapyr (2) POST ± chlorsulfuron (IBS)

All herbicide treatments were applied with a spray boom delivering 100 L ha^-1 water volume at a pressure of 200 kPa. As per label recommendations, 1% (v/v) paraffinic oil mixed with non-ionic surfactant Hasten (Crop Care Australasia Pty. Ltd., Queensland, Australia) was added to IMI herbicide in tank mix as per the product labels.

IMI herbicide residue testing in the soil: Soil samples were taken from three random spots in each plot before sowing of the second-year crop and bulked depth wise at 0-10 cm, 10-30 cm, and 30-50 cm of the soil layer to study the residues of imazapyr, imazamox and imazapic from the previous season.

Tares, bedstraw and bifora density were assessed with a 0.25-m² quadrat placed at three random locations in each plot. Assessment of broadleaf weed plant density was taken before and after POST herbicide application. Broadleaf weeds’ seed/pod set assessments were made 14 to 16 weeks after planting (WAP) in October before seed shed from three spots in each plot with a 0.25-m² quadrat.

Lentil, wheat, barley and canola seed yield was determined by harvesting plots with a small-plot harvester. Seeds were cleaned in the laboratory to remove weed seeds, and yield was determined. A seed subsample of 500 g of the all crops was used to determine the 100-seed weight.

We would like to acknowledge the statistical designs provided by Helena Oakey and Annie Conway. We thank all the SARDI Clare team for their support in the research work in this project.

Requested data must reference the Objective ID to request the dataset. Requests will be assessed and may not be released due to confidentiality arrangements and specific licencing agreements.

Objective ID: fA3156100