Benefits of organic fertiliser and crop rotation for beetles and soil-dwelling creatures

The researchers found that cropland treated with organic fertiliser, and which included perennial ley (legumes and grasses for feed or fallow) in the crop rotation, had more soil-dwelling creatures than cropland treated with mineral fertiliser. They suggested that this treatment benefits farmers, since soil-dwelling creatures such as mites help improve soil quality, while some beetles eat crop pests like aphids.

Previous studies have suggested that a return to certain traditional ‘diversifying’ farming practices could help restore ecosystem services without decreasing yield. Specifically, using organic fertilisers and including perennial ley in crop rotations can enhance soil organic carbon pools. In turn, these pools support wildlife that provide ecosystem services including biological pest regulation, soil fertility and nutrient cycling.

However, previous studies have typically been short-term in duration, or only investigated one diversifying practice at a time. This new study from Sweden advances our knowledge of the impact of diversification on biodiversity by looking at the effects of both organic fertilisers and perennial ley on arthropod numbers over time. These include insects and other ‘mini beasts’ such as spiders, mites and millipedes.

The researchers compared the effects of three different diversification practices in 19 conventionally-farmed oat and barley fields in south-west Sweden. These were:

• organic fertiliser (manure and slurry) and including perennial ley in rotations;
• organic fertiliser and annual crop rotation;
• mineral fertiliser and annual crop rotation.

All fields had received these treatments for at least six years. The researchers counted above- and below-ground species found at eight points in each field, on three separate occasions between May and July 2020.

The results reveal much higher numbers of soil-dwelling creatures (specifically, mites and springtails) in the fields which used organic fertiliser and included perennial ley in their rotation. Among above-ground predatory species, rove beetles (staphylinids) were also most abundant in these fields. Fields where mineral fertiliser had been applied had the lowest abundance of mites, springtails and rove beetles.

The researchers point out that combining perennial ley with organic fertiliser helps keep soil moist. This management practice is, therefore, particularly beneficial for soft-bodied creatures in the soil, such as mites which dry out easily.

There were no differences in abundance between the fields for above-ground prey species, such as flies and weevils, and little difference for carabid beetles. The researchers note that the mineral- fertilised fields contained more weeds, the seeds of which are a source of food for carabid beetles.

The researchers conclude that cropping practices which combine organic fertilisation with extended crop rotations that include perennial leys have the potential to boost biodiversity, increase the resilience of below- and above-ground species and support the ecosystem services they provide without decreasing yields.

Source:

Heinen, J., Smith, M.E., Taylor, A., and Bommarco, R. (2023) Combining organic fertilisation and perennial crops in the rotation enhances arthropod communities. Agriculture, Ecosystems & Environment. DOI: 10.1016/j.agee.2023.108461.

To cite this article/service:

“Science for Environment Policy”: European Commission DG Environment News Alert Service, edited by the Science Communication Unit, The University of the West of England, Bristol.

Notes on content:

The contents and views included in Science for Environment Policy are based on independent, peer reviewed research and do not necessarily reflect the position of the European Commission. Please note that this article is a summary of only one study. Other studies may come to other conclusions.