herbicide

Seedbanks of arable east Scotland 2007

The lack of a baseline on which to assess differences between farming preferences and soil types necessitated this extensive study of seedbanks in representative fields in the east of Scotland from Moray, through Aberdeenshire, Angus, Fife and the Lothians to the Borders. Soil samples were collected in 2007 from more than 100 fields. The aims were to see whether seedbanks differed in relation to soil, latitude, crop rotation and management inputs. The information will contribute as a reference and baseline along with data on soil physical and microbiological properties, vegetation, agronomy and yield as part of the RERAD workpackage on Sustainable Crop Systems.

The methodology, using the emergence method,  was similar to that used in the FSEs. Soil samples were taken by field teams from SCRI and SAC and laid out in trays in the glasshouses at SCRI in Dundee. The first flush of seedlings, mainly of spring-germinators and generalist species was measured for several months after sampling. In the autumn of 2007, the soil in each tray was remixed and emergence was again measured, this time capturing the autumn-germinators. The advantage of this substantive database is the wide range of associated measurements, much more than in the FSEs, that should enable us to quantify the seedbank's dual role of weed burden and base of the arable food web.

Set aside experiments 1989-1997

Field experiments on set aside were funded by the UK government and managed by ADAS at Boxworth, Drayton, Gleadthorpe, and High Mowthorpe between 1989 and 1997. Each site consisted of replicated small plots on which a range of set aside treatments, including natural regeneration and various sown covers, were established for five years, after which most of the plots returned to arable cropping. Several plots remained in arable cropping throughout the period as a comparator.

SCRI's contribution was initiated by Harry Lawson, now retired, and consisted of measuring the seedbank by the extraction method at the beginning, after the five years of set aside and after two further years following return to arable cropping. The experiment demonstrated the strong effect of local conditions on the arable seedbank, notably that the seedbank can be amplified or suppressed by the management imposed largely irrespective of the species present. The results contributed to the understanding of the seedbank's role as both the weed burden and the arable plant biodiversity.

Contact: Geoff Squire

The FSEs (the UK's GM crops trials) 1999-2005

All seedbank measurements in the FSEs were carried out by SCRI using the emergence method applied to soil sampled from the 250 or so sites used in the experiment by field staff from CEH, Rothamsted Research and SCRI.

The method was developed in 1999 on three spring and four winter oilseed rape sites. On the basis of these initial measurements, the group estimated that differences of 1.5- to 2- fold in seedbank density between treatments would be detected from around ten samples of each one litre of soil from each treatment (half field). In the event, the estimates proved correct.

From 2000 onwards, a baseline sample was taken before the treatments were applied at each of the 250 sites, and repeat samples from the same locations 12 and 24 months later. At the height of activity in 2001, thousands of trays containing soil were spread throughout several large cubicles in glasshouses equipped with temperature control and shading. In all, SCRI's seedbank records in the FSE comprise the largest arable seedbank survey in the UK.

The Talisman low input experiments 1990-1996

TALISMAN was series of experiments funded by the UK government and managed by ADAS at High Mowthorpe, Drayton and Boxworth between 1990 and 1996. Each site consisted of replicated small plots in which crops of cereals and breaks were grown at full and half doses of herbicides, fungicides, insect pesticides and fertiliser.

SCRI's contribution was initiated by Harry Lawson, now retired, and consisted of measuring the seedbank in high and reduced herbicide plots. The seedbank was measured by the extraction method from cores of soil taken before the treatments were applied and after three and six years. In some reduced herbicide treatments, the seedbank increased more than 100-fold after the six years. Treatments and sites were compared in terms of seedbank community parameters derived from species-accumulation and similar devices. The results contributed to the understanding of the seedbank's role as both the weed burden and the arable plant biodiversity.

Papers and reports

Squire, G.R., Roger, S., Wright, G. 2000. Community-scale seedbank responses to less intense rotation and reduced herbicide input. Annals of Applied Biology 136, 47-57. doi: 10.1111/j.1744-7348.2000.tb00008.x

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