Action: Plant crops in spring rather than autumn
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- A total of nine studies from Denmark, Sweden and the UK looked at the effects of sowing crops in spring or autumn on farmland wildlife. Five studies (including one replicated controlled trial, and a review) found that planting crops in spring rather than autumn resulted in higher numbers of farmland birds, weed diversity or weed density and one arable weed species produced more fruit on spring-sown crops.
- A review found one study from the UK showing that four out of five species of arable weed produced more fruits on autumn-sown crops. A second review found one study showing that there were more invertebrates in winter wheat than spring wheat.
- A replicated study from the UK found that winter and spring sown crops were used for different broods by Eurasian skylarks. A replicated site comparison found arthropod abundance was higher in autumn barley in early summer and spring barley in late summer. A replicated, controlled study in Sweden, found that northern lapwings nested on spring-sown crops more than expected based on their availability, but hatching success on spring crops was lower than on autumn crops.
This intervention involves planting crops in spring rather than autumn. Changes in farming practice in northern Europe have included a shift from sowing crops in spring to sowing them the preceding autumn/winter. This change is considered to have adversely affected farmland biodiversity including invertebrates and farmland birds (see, for example, Donald & Vickery, 2000).
Donald P. F. & Vickery J. A. (2000) The importance of cereal fields to breeding and wintering skylarks Alauda arvensis in the UK. Pages 140-150 in: N. J. Aebischer, A. D. Evans, P. V. Grice and J. A. Vickery (eds) Ecology and Conservation of Lowland Farmland Birds, British Ornithologists Union, Tring.
Supporting evidence from individual studies
A replicated study in 1992 and 1993 within the South Downs Environmentally Sensitive Area, Sussex, UK (Wakeham-Dawson 1995) found that winter and spring-sown crops were used for different broods by Eurasian skylark Alauda arvensis. Winter-sown crops tended to be used more for first brood nesting skylarks (first brood period: 8-15 males/km², second: 4-9), whereas spring-sown crops were used more for the second brood (first brood period: 3-4 males/km², second: 7-14). Four arable, 10 mixed and three pastoral farms were studied. Skylarks were sampled by mapping breeding males during two counts along transects on 12-17 farms from April to June.
A replicated, controlled study of arable fields at three sites within the TALISMAN MAFF-funded experiment in England (Jones et al. 1997) found that weed density tended to be higher in plots with increased spring cropping compared to those with winter dominated cropping. Seed bank density depended on site. At Boxworth, seed bank density was higher on increased spring cropping rotations (8,780-25,824/m²) compared to winter dominated cropping (2,172-2,209/m²). In contrast, at High Mowthorpe, seed densities were higher with winter cropping (11,300-16,231/m² vs 1,764-3,181/m²). Total plant density tended to be higher in plots with increased spring cropping than with winter dominated cropping (4-18 vs 3-9/m²). There were differences between species, and at High Mowthorpe, some had significantly higher populations on plots with winter cropping. At Boxworth there were two replicates in two blocks, at the other two sites, there was one replicate in three blocks. Seed banks were sampled at Boxworth and High Mowthorpe after harvest from three sub-samples (60 combined soil cores) in each plot. Weed density was sampled in 15 quadrats/plot at the three sites after harvest (August-September) and in October-November.
A 1998 literature review (Sotherton 1998) looked at the effect of agricultural intensification and the role of set-aside on the conservation of farmland wildlife, particularly endangered annual arable wildflowers and gamebirds. It found one UK study comparing arable weeds in spring and autumn-sown cereals showing that rough poppy Papaver hybridum, shepherd's-needle Scandix pecten-veneris, corn buttercup Ranunculus arvensis and common corncockle Agrostemma githago produced significantly more fruits/plot in autumn-sown than spring-sown cereals. In contrast broad-fruited cornsalad Valerianella rimosa produced significantly more fruits in spring-sown crops (Wilson 1994).
Wilson P. J. (1994) Botanical diversity in arable field margins. Pages 53-58 in: N. D. Boatman (ed) Field Margins-Integrating Agriculture and Conservation, BCPC Monographs, 58.
A replicated site comparison study in 1988-1992 in 19 arable fields in Denmark (Hald 1999) found that weed diversity in unsprayed crop margins was over 25% lower in winter cereals than in spring cereals. Of the 114 weed species found, 97 were present in spring cereals compared to 87 in winter cereals. Of the species with known germination seasons, 94% were able to germinate in spring cereals whilst 64% were able to germinate in winter cereals. In addition, important food plants for arthropod herbivores occurred at greater densities and higher relative abundance in spring cereals. Experimental plots were 6 x 20 m, with crop rotation determined by the farmer. Each plot was sampled in spring each year, using 10 permanent 0.1 m circles/plot. Only data from permanently unsprayed plots in fields that supported at least one winter and one spring cereal sample were used in the analysis (72 plots).
A replicated, site comparison study between 1984 and 1994 in Västmanland, Sweden (Berg et al. 2002), found that northern lapwing Vanellus vanellus nested on spring-sown crops more than expected based on their availability, and on autumn sown crops less than expected. However, hatching success on spring crops was lower than on autumn crops (29-50% for 1,236 nests on spring crops vs approximately 85% for 27 nests on autumn crops).
A 2003 literature review in Europe (Bat Conservation Trust 2003) found one study that reported that winter wheat supported higher numbers of invertebrates than spring wheat (Green 1984).
Green R.E. (1984) The feeding ecology and survival of partridge chicks (Alectoris rufa and Perdix perdix) on arable farmland in East Anglia. Journal of Applied Ecology, 21, 817-830.
A before-and-after site-comparison study in 2000-2005 in Bedfordshire, England (Henderson et al. 2009), found that fields sown with wheat in spring held significantly more Eurasian skylark Alauda arvensis, seed-eating songbirds and insect-eating birds than winter-sown wheat. In addition, 20 bird species showed significant population increases on a 61 ha site where the area of spring-sown wheat and naturally regenerated set-aside was increased over the study period. Increases were lower or absent on an 80 ha area of farmland adjacent to the experimental area and without the land use change. Five species were recorded breeding for the first time after management started. Ten species showed no significant increase on the study site, whilst none decreased significantly. The biggest increases occurred in the first three years of management and were higher for farmland birds than for woodland birds.
A replicated site comparison study in 2004 of autumn-sown and spring-sown barley on four farms in Scotland (Douglas et al. 2010) found that arthropod abundance was higher in autumn barley in early summer and in spring barley in late summer. Arthropod abundance was significantly higher in autumn barley from April to June (autumn barley: 8-21/sample; spring: 3-14), consistent with earlier crop development. The reverse was true in July and August (autumn barley: 15-23; spring: 20-26/sample). Abundances of individual arthropod orders varied slightly between the two sowing regimes. A total of five spring and five autumn barley fields were selected from four farms (two of each crop type). No insecticides were applied, but fields received one or two herbicide applications. Arthropods were sampled on five occasions in each field (April-August 2004) using a leaf vacuum (15 cm diameter). Sampling was undertaken at intervals (5 or 30 m) along 2-5 parallel transects (100 m apart) across the width of each field.
A replicated paired site comparison study in 2004 of autumn-sown wheat and spring-sown barley in Sweden (Eggers et al. 2011) found that there were significantly greater numbers of ground-foraging breeding birds in spring-sown cereals. There were 0.8 species/ha in spring-sown compared to 0.5 species/ha in autumn-sown cereal plots. Territory densities of northern lapwing Vanellus vanellus and northern wheatear Oenanthe oenanthe were also higher in spring-sown (lapwing: 0.08 territories/ha, wheatear: 0.12) compared to autumn-sown cereal plots (lapwing: 0.02; wheatear: 0.05). There was no effect of sowing time on Eurasian skylark Alauda arvensis or yellowhammer Emberiza citrinella breeding density. In spring-sown plots, numbers of species decreased significantly as the proportion of autumn-sown cereals in the surrounding landscape increased. Forty-one independent pairs of autumn-sown wheat and spring-sown barley plots were selected, each centred on an infield non-crop island. Non-crop islands were surveyed for cover of trees, shrubs and weeds and cereal height was measured on five occasions in each field. All birds were recorded within a radius of 100 m from the centre of each plot during five point counts of seven minutes (mid-May to end of June).
- Wakeham-Dawson A. (1995) Hares and skylarks as indicators of environmentally sensitive farming on the South Downs. PhD thesis. The Open University.
- Jones N.E., Burn A.J. & Clarke J.H. (1997) The effects of herbicide input level and rotation on winter seed availability for birds. 1997 Brighton Crop Protection Conference - Weeds, Conference Proceedings, Brighton, 1-3, 1161.
- Sotherton N. (1998) Land use changes and the decline of farmland wildlife: an appraisal of the set-aside approach. Biological conservation, 83, 259-268
- Hald A.B. (1999) The impact of changing the season in which cereals are sown on the diversity of the weed flora in rotational fields in Denmark. Journal of Applied Ecology, 36, 24-32
- Berg Ã., Jonsson M., Lindberg T. & Källebrink K.G. (2002) Population dynamics and reproduction of northern lapwings Vanellus vanellus in a meadow restoration area in central Sweden. Ibis, 144, 131-140
- Bat Conservation Trust (2003) Agricultural practice and bats: A review of current research literature and management recommendations. Defra report.
- Henderson I.G., Ravenscroft N., Smith G. & Holloway S. (2009) Effects of crop diversification and low pesticide inputs on bird populations on arable land. Agriculture, Ecosystems & Environment, 129, 149-156
- Douglas D.J.T., Vickery J.A. & Benton T.G. (2010) Variation in arthropod abundance in barley under varying sowing regimes. Agriculture, Ecosystems & Environment, 135, 127-131
- Eggers S., Unell M. & Part T. (2011) Autumn-sowing of cereals reduces breeding bird numbers in a heterogeneous agricultural landscape. Biological Conservation, 144, 1137-1144