SOWAP Results - Terrestrial Biodiversity

Conservation tillage techniques (left-hand side) were compared with mouldboard ploughing (right-hand side) where the soil is inverted

The results presented in this section are from farms across the 3 countries. Soil microbiology and earthworms were chosen as indicators of soil health. Above-ground, the responses of soil-surface arthropods and birds to conservation tillage were studied in Hungary and the UK .

For more information about the issues facing farmland biodiversity go to Biodiversity and agriculture and on SOWAP's work SOWAP and biodiversity

SOIL BIODIVERSITY

Conservation tillage benefits soil microbial communities

Microbial biomass increased under conservation tillage compared to mouldboard ploughing.
Microbial communities in conservation tillage soils comprise more soil fungi

Soil micro-organisms have important functions in the soil because of their involvement in carbon and other nutrient cycling and in regulating plant and animal communities. Tillage practices and the management of residue have a strong influence on soil microbiology by modifying the environment below ground and the availability of food.

After three years, conservation tillage soils contained significantly greater microbial biomass than those subjected to mouldboard ploughing (Figure 1). However the response differed between countries. In Belgium , conservation tillage resulted in significantly greater biomass. In Hungary biomass concentrations were stable under conservation tillage but decreased under mouldboard ploughing. At the Loddington site in the UK , biomass increased over the three year period under both tillage types, with the conservation tillage soils containing significantly higher biomass than mouldboard plough soils at the end of the project in 2006. There was no change in biomass at the Tivington site.

Figure 1: Soil microbial biomass concentrations averaged across sites in Belgium, Hungary and UK (Loddington) in relation to tillage treatment at the start of the project in spring 2004 and at the end in spring 2006. MP = mouldboard ploughing and CT = conservation tillage.

Whilst tillage had little impact on overall microbial community structure, the proportion of fungi in the soil increased under conservation tillage when data was averaged across all the sites. Fungi benefit soil structure by producing exudates that bind soil particles together along with their hyphae. Breaking fungal hyphae by mouldboard ploughing is detrimental to soil fungi and increases the soil’s potential to be lost by erosion.

Microbial communities also showed significant variation over time with different structures present in spring and autumn.

Conservation tillage linked to an increase in earthworm numbers

In Belgium and Hungary there were more earthworms in conservation tillage soils than in mouldboard ploughed soils
In the UK the link between earthworm numbers and soil management was inconsistent

Earthworms are very important for maintaining a healthy soil. They help enhance soil structure when they incorporate crop residue; they re-distribute soil nutrients and improve water infiltration. Intensive cultivation systems like those using a mouldboard plough have a negative effect on earthworms. Such machinery directly causes injury and death and indirect effects like changes in soil temperature, soil moisture and decreased availability of food further decrease numbers.

In Belgium conservation tillage consistently provided a better environment for earthworms (Figure 2). This was also true in Hungary .

Numbers of Earthworms

Earthworm Biomass

Figure 2: Numbers and weights of earthworms in mouldboard ploughed (MP) and conservation tilled soils (CT1 + CT2) at the Belgian demonstration site.

In the UK , there was no clear relationship between the different soil management systems and earthworm numbers. This variability is the result of a complex interaction of the weather, crop residue, previous crop, time of drilling and earthworm sampling date.

In all countries, there were more juvenile than adult earthworms. Of the adults found there were higher numbers of those earthworms living in the surface layers of the soil than those typically found lower down the soil profile.

ABOVE-GROUND BIODIVERSITY

Conservation tillage is beneficial for arthropods

In Hungary , conservation tillage encouraged larger numbers of ground beetles, rove beetles, beetle larvae, harvestmen and spiders
In the UK , the number of arthropods was more affected by the previous crop than by soil management

Arthropods are important as a food source for several declining farmland bird species like grey partridge and also as predators of crop pests like aphids and weed seeds. The two families of surface-active beetles most often seen in cereal fields are ground (Carabidae) and rove (Staphylinidae) beetles, and several families of spiders including wolf (Lycosidae) and money (Linyphiidae) spiders.

In two out of three fields in Hungary in May 2005, higher numbers of arthropods were found in conservation tillage areas than in mouldboard ploughed areas (Figure 3). However, in June and July of the same year, there was less difference between the soil management treatments.

The only arthropod group to be found in greater numbers in the ploughed treatment were the Opiliones (harvestmen), but this was only the case in one of the three fields

Figure 3: Mean number of arthropod groups in conservation tillage and mouldboard ploughed areas of a field in Hungary in May 2005. MP = mouldboard plough, CT = conservation tillage

In the UK , the previous crop had the greatest impact on the numbers of arthropods. One of the reasons for this might be the greater diversity of cropping in the UK compared to Hungary . In Hungary , winter wheat and maize were the only crops in the rotation on two of the three fields. Soil management had an impact on only two species of Carabid beetle Notiophilus biguttatus and Bembidion guttula in the UK . Larger populations were found on the conservation tillage fields but the effect was not consistent e.g . higher numbers of Notiophilus biguttatus were found in March and July but not in May.

Conservation tillage benefits farmland birds

Skylarks and other seed-eating songbirds selected fields established by conservation tillage in winter in preference to mouldboard ploughed fields
Invertebrate feeders also showed a preference for conservation tillage fields in winter
Ground-nesting birds responded positively to conservation tillage , especially skylarks

Skylarks and other seed-eating songbirds showed a preference for conservation tillage fields in winter but the benefits are context dependent. In the UK , numbers of birds, even on conservation tillage plots, were very low. The numbers of birds recorded in Hungary were much higher (Figure 4). This was most notable on fields going into maize, which were effectively weedy wheat stubbles.

Figure 4: Use of arable fields in Hungary and the UK by wintering seed-eating birds. MP = mouldboard plough, CT = conservation tillage.

Furthermore, in summer in the UK , there were more pairs of skylarks, nesting began earlier, and the breeding season was longer on conservation tillage fields (Figure 5). Additional crop residues on the soil surface left by conservation tillage (in this particular case, a no-till farm) may allow skylarks to use winter-sown cereal fields at an earlier stage of crop development, and so to breed earlier in the summer. In addition, adult skylarks feeding chicks in conservation tillage fields flew about half as far to get food as those in mouldboard ploughed fields, suggesting greater food availability.

Figure 5: Timing of skylark nesting attempts (in days after 1st April) in relation to tillage treatment, at Rutland, UK, in summer 2005. MP = mouldboard plough, CT = conservation tillage

Studies of captive greenfinches showed no difference in foraging rate with tillage practice, despite there being more seeds on the surface of conservation tillage plots than mouldboard plough plots. However, there was a positive relationship between seed density on the soil surface and foraging rate, indicating that the generally higher seed densities on conservation tilled soils have greater potential than mouldboard ploughed soils to be beneficial, but only if the density of seeds exceeds a threshold.

Invertebrate feeding birds also favoured conservation tillage fields in winter. This preference is also likely to be food-related.

CONSERVATION TILLAGE BENEFITS FARMLAND BIODIVERSITY

SOWAP has demonstrated that both above and below-ground biodiversity can benefit from conservation tillage. Reducing the number and intensity of soil management operations and adding organic matter through crop residue (or cover crops) practice improved the conditions under which important soil-living creatures like earthworms and microbes thrive.

Fields under conservation tillage benefited farmland birds due to the provision of more food resources and better camouflage for nests. However, to supply the year-round needs of all farmland species, conservation tillage needs to be complemented by other land management options e.g. the retention of weedy stubbles. With its other resource-protection benefits, conservation tillage could be an option for inclusion in agri-environment schemes and widespread application may provide birds with resources that are otherwise being lost through management of cropped land.

On the farm, the farmer benefits from the enhanced soil biodiversity community working to improve the health of the soil. This is the basis of a productive cropping system. More beetles and spiders can help the farmer protect his crops from pests and diseases. Birds, at the top of the food chain, provide the farmer and the rest of society with a visible demonstration of the health of the agricultural ecosystem.

This report is based on the work of Krisztina Bádonyi, Szabolcs Benke , Dr. János Farkas and Prof. András Zicsi in Hungary; Heidi Cunningham and Avril Rothwell at Harper Adams and Rob Field and Richard Bradbury of the RSPB, all in the UK.