Dataset: Broadbalk Weed Survey Data 1991-2021

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Summary

This dataset consists of the relative annual frequencies of all non-crop plant species ('weeds') recorded in all eighteen plots of section 8 of the Broadbalk wheat experiment, 1991-2021. Section 8 has not received any herbicides in its history - in contrast to the other sections of Broadbalk which have received herbicides since 1964. Broadbalk section 8 is one of the few arable sites in the country where herbicides have never been applied. Consequently it is populated by a rich diversity of arable species, some very rare elsewhere in England. Broadbalk continues to act as a valuable resource for weed investigations 180 years after it was established, for example Moss et al. (2004).

There have been various surveys of weeds on Broadbalk wheat experiment since its conception in 1843, but not a consistent methodology in these. The first plot-by-plot surveys of weed species were done in 1869 recording the presence of species. The first phase of annual surveys was between 1933-1979 prior to the current layout of sections. The current weed survey was started on section 8 in 1991 and has continued annually ever since - although not on years when that section is in fallow: 1994, 2001, 2008, 2015, 2016 and 2022. Section 8 (called section VA 1958-1967) was created in 1968 when the experiment was divided into its present layout (Broadbalk plan today).

The current assessment method records the presence of individual weed species in 25 random quadrats (0.1m²) per plot. The plots receive differing types and rates of fertilizer treatments and the weed species reflect these. Each year all 18 plots are surveyed meaning 450 quadrats are assessed per year, usually in June. Frequencies refer to the total number of quadrats in which a weed is recorded, the maximum being 25 per plot and 450 across all plots in the section. This method is more appropriate for detecting long-term trends in weed frequencies and population differences between plots than the earlier surveys and provides a comprehensive set of 20 years of data for weed studies.

There have been 60 different species identified over the 30-year duration of this current survey, but many of these only occur sporadically and around 30 of these are currently recorded annually. This site also provides an invaluable reserve for seven nationally rare or uncommon species including corn cleavers (Galium tricornutum), corn buttercup (Ranunculus arvensis), shepherds needle (Scandix pecten-veneris) and prickly poppy (Papaver argemone). This is now the only location in the UK where corn cleavers is known to occur naturally.

This valuable resource, and associated data, allows the study of long-term interactions between plant species, an opportunity to test current controversies in population and community ecology such as equilibrium theories which require data on resource requirements and loss rates. The long time series enables the detection of cycles in the abundance of individual species; to determine to stability of weed communities; it enables various weed investigations including weed population ecology; studies on the effects of fallowing on the weed seed bank; seed dormancy and persistence; agroecology and population dynamics of individual weed species. Recently, molecular approaches have been used to study the genetic diversity of weeds found on Section 8, this rare herbicide-free arable plot. On plots where inorganic nitrogen fertiliser has been applied, potential yield losses from weeds have consistently increased since 1969. This was explained by a warming climate, measured as air temperature averaged over the growing season for the weeds, and a shift towards shorter crop cultivars (Storkey et al 2021). Weeds on Broadbalk may genetically more competitive now due to selection for more competitive individuals

This dataset also provides the yields of the plots both with and without the weight of the weed seeds. The percentage of weed seeds in the total grain varies between greatly, between 1-71.8% of the total grain yield. The year 2012 was a particularly high weed year followed by 2007 and 2013.

Herbicide Resistance Studies: This section 8 of Broadbalk is an important source of susceptible seed of the weed Alopecurus myosuroides, blackgrass. It provides an excellent standard susceptible strain for use in herbicide-resistance assays, as having never received herbicides the grass-weed has never evolved herbicide resistance. See "Herbicide resistance in Alopecurus myosuroides: The value of routine testing of seed samples submitted by farmers since 1985", Cook et al. Weed Research (2023).

Methods

The assessment method records the presence of individual weed species in 25 random quadrats (0.1m2) per plot. Each year all 18 plots were surveyed meaning 450 quadrats are assessed per year, usually in June. Frequencies refer to the total number of quadrats in which the species is recorded, the maximum being 25 per plot and 450 across all plots in the section.

The weed survey generally takes place in June, precise dates are indicated in the dataset.

The yield correction for weed seed contamination, from 1992: Two samples (1kg each) were taken from the grain samples harvested from each plot. These samples were cleaned with a Petcus seed cleaner fitted with a 3.3mm round hole top sieve and a 2.0mm slot type bottom sieve. The sample was tipped directly onto the top sieve, not via the air stream separator. Four fractions were collected and weighed: a. >3.5mm retained on top sieve, mainly threshed heads, b. <2.0mm passed through bottom sieve, mainly weed seeds (black-grass, black-medick, shepherds needle) and some small grains, c. retained on bottom sieve, first fraction from rotary separator, mainly wheat grain with a small amount of weed seed contamination (mainly vetch), d. retained on bottom sieve, second fraction from rotary separator, a variable mixture of wheat and vetch. Sample d was sub-sampled to determine grain content. Two sub-samples (each ~5g) were taken, the grain & weed seeds separated manually, and the two fractions weighed. This determined the d grain is each sub-sample and the mean of the two samples calculated. This value was used to calculate the weight of cleaned grain in the entire d fraction. Cleaned grain weight was then calculated from fraction c plus grain weight of fraction d for each of the two samples collected per plot. Total cleaned weight was then expressed as a % of the total sample weight, and the mean of these two samples calculated. Thus a single % correction factor was derived. The combine yields (t/ha corrected to 15%moisture content / 85% dry matter) were then adjusted using this correction factor to derive a clean 'weed free' grain yield (t/ha) for each plot.

Technical Information

No weeds present in fallow years, due to frequent cultivation which kills emerging weed plants.

Broadbalk Section 8 Yield of grain from combine, yield of clean grain, 1992-2022: Clean grain excludes grain <2mm and >3.5mm. This excludes the weed seeds.

Section 8 is fallowed frequently to control weeds (i.e no crop is grown).

Related Documents

• Broadbalk Fertilizer and Manure Treatments 1852-2021 :
• Broadbalk Today revised 2018 :
• Broadbalk Weeds :
• Cook et. al. (2023) Weed Research. Herbicide resistance in Alopecurus myosuroides: :
• Storkey et al. (2021). Agricultural Intensification and climate change... Global Change Biology :
• Moss et al. (2004). The Broadbalk long-term experiment at Rothamsted: ...about weeds. Weed Science :

Contributors

• Sarah Perryman: Data curator
• Sarah Perryman: Data collector
• Richard Hull: Data collector
• Margaret Glendining: Data curator
• Nathalie Castells: Data manager
• Stephen Moss: Data collector
• Steve Freeman: Data collector
• Jonathan Storkey: Data collector
• Shona Merten: Data collector
• Caroline Archer: Data collector
• Dave Frearson: Data collector
• John Cussans: Data collector
• Anna Swain: Data collector
• Esther Trevis: Data collector
• Emma Browne: Data collector
• Dale Kirsop: Data collector
• Thomas Baldwin: Data collector
• Caroline Elliott: Data collector
• Susan Hughes: Data collector
• Veronique Potier: Data collector
• Joanna Banks: Data collector
• Ian Wynne: Data collector
• Katherine Berry: Data collector
• Sara Day: Data collector
• Zoe Hughes: Data collector
• Angiolina Albertini: Data collector
• Peter Lutman: Data collector

Dataset Access and Conditions

Rights Holder

Rothamsted Research

License

This dataset is available under a Creative Commons Attribution Licence (4.0).

Cite this Dataset

YOU MUST CITE AS: Richard Hull, Stephen Moss, Sarah Perryman (2023). Dataset: Broadbalk Weed Survey Data 1991-2021 Electronic Rothamsted Archive, Rothamsted Research https://doi.org/10.23637/rbk1-weeds_1991-2021_01

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