seedbank

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

Wild arable plants - diversity and function

The ecology and biology of wild arable plants are poorly understood. Of the more than 250 plant species to be found on arable farmland, typically five to 10, among which are wild oat, blackgrass, barren brome and cleavers, constitute the main weed burden of arable cropping. Many of the rest, particularly the broadleaf (dicotyledonous) species, support an arable food web that includes insect groups, mammals and birds. Despite the economic, ecological and aesthetic importance of wild arable plants, embarrassingly little is known about their ecology and genetic diversity.

Our first research paper in this new topic demonstrated the lack of basic information for even the common species (Hawes et al., 2005). If arable cropping systems are to be sustainable, then co-existence between crops and weeds must be managed with minimum or no herbicide application. To achieve this, fundamental and strategic research is necessary into the way wild arable plants respond to crops, weather and field management.

The seedbank

Seeds from the arable seedbank - photograph by Gladys Wright/Stewart MaleckiBuried living seed - the seedbank - is central to the composition and succession of disturbed vegetation, allowing regeneration after agricultural or natural clearing of the existing plant cover. In arable-grass systems, the seedbank is the source of both the weed burden and the vegetation that supports the arable food web. Of around 250 species typically found in arable regions, only five to 10 are economically important as competitors to crops. Few of the poisonous species that were once a concern now remain in fields. Most of the other seedbank species have been reduced, in particular the broadleaf or dicotyledonous species that provide food and habitat for detritus feeders, herbivores, parasitoids, predators and pollinators. Knowing the seedbank is therefore essential for balancing the weed burden and biodiversity.

Plant population and community modelling

The objective of plant population and community modelling in the Agroecology group is to understand, and where necessary anticipate, the effects on arable vegetation of technical innovations and global change, and thereby to understand the role of the vegetation in the sustainability of the arable system as a whole.  System-level responses, such as primary production, nutrient retention and biodiversity, emerge over time, often unpredictably, from complex ecological and evolutionary processes. By developing models of plant populations and communities, we are able to assess the response of arable vegetation in a way that can't be addressed by experiment or observation alone.

Our current focus is the influence of the genetic and functional characteristics (life-history traits or their physiological determinants) of plants on system-level properties. A common thread is the definition of populations and communities in terms of the genetic and functional variation of individuals. Using the individual enables intra- and inter-specific variation to be presented on a common scale and both ecological and evolutionary processes to be combined in a single model framework.

Trait characterisation in crops

Photograph of growing-tubes in SCRI glasshousesCrop productivity has increased dramatically in recent decades through a combination of improved arable management and breeding of higher yielding crop genotypes.

Further increases in productivity are needed to cope with growing demands for food. The price, availability and high energy costs (carbon footprint) of inorganic fertiliser mean that food production will need to be achieved with fewer chemical inputs and with greater emphasis on a sustainable approach to arable cropping. 

New crop genotypes that require less chemical fertiliser and pesticide for a given level of yield could be developed by characterising plant traits associated with reduced nutrient requirements and high pest tolerance.

Contact: Alison Karley

Plants and plant communities

Photograph of happy field workers sampling plantsResearch in Plants and Plant Communities aims to define those properties of crops and arable plants that would maintain yield and the purity of yield while reducing the environmental footprint of cropping. The work includes basic studies of plant processes such as germination, flowering and nutrition, genetic and physiological variation in model crops and arable plants, the ecology of plant (seedbank) communities, plants as the base of the arable food web and models of geneflow, selection and evolution. The practical output will be combinations of plant traits that can be targeted in crop improvement or encouraged by agronomy. Disciplines and methods include plant physiology, genetics, statistics, modelling, microscopy and field survey.

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