A huge 42 foot Caterpillar Lexion combine harvester in New South Wales. One of only 3 in Australia. Creative Commons - https://commons.wikimedia.org/wiki/File:CAT_combine_harvester.jpg - Attribution 2.0 Generic (CC BY 2.0)
A huge 42 foot Caterpillar Lexion combine harvester in New South Wales. One of only 3 in Australia. Creative Commons - https://commons.wikimedia.org/wiki/File:CAT_combine_harvester.jpg - Attribution 2.0 Generic (CC BY 2.0)

EXPERT REACTION: Farm machines as heavy as dinosaurs could wreck 20% of the world’s croplands

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Peer-reviewed: This work was reviewed and scrutinised by relevant independent experts.

Researchers have shown that, globally, increasingly heavy farm machinery is stressing the deeper layers of soil underneath the surface to the point it's now exceeding the safe limits for soil ecology. Global food production may be affected, as one-fifth of productive land for crops is at risk of subsoil compaction, including Australia. While not in that grouping, parts of NZ were also classed as at relatively high risk. The total weights of modern farm machines are now almost as heavy as the biggest dinosaurs, the sauropods, and the authors call for stricter design of farm machinery to protect deeper soils.

Journal/conference: Proceedings of the National Academy of Sciences

Research: Paper

Organisation/s: Swedish University of Agricultural Sciences (Sweden), Department of Agroecology & Environment, Agroscope, Swiss Federal Institute of Technology (Switzerland), Desert Research Institute (USA)

Funder: We acknowledge funding by the Swiss National Science Foundation (project 406840-143061) that supported the inception of this line of work and funding by the Swedish Farmers’ Foundation for Agricultural Research (Stiftelsen Lantbruksforskning, grant O-17-23-959) and from Swedish Research Council for Sustainable Development (FORMAS) (grant 2020-02726, ICT-AGRI-FOOD project implementation of soil compaction risk assessment system – end-user's evaluation of potentials and barriers [SoCoRisk]) to T.K.

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Expert Reaction

These comments have been collated by the Science Media Centre to provide a variety of expert perspectives on this issue. Feel free to use these quotes in your stories. Views expressed are the personal opinions of the experts named. They do not represent the views of the SMC or any other organisation unless specifically stated.

Dr Wei Hu, Senior Scientist (Soil Physics & Soil hydrology), Plant & Food Research

Farm machinery use has greatly improved the efficiency of crop production. In the last 60 years, both total weight and tyre size of combine harvesters have increased. As a result, surface soil is under almost constant surface contact stress. However, the increase in subsoil stress, and hence subsoil compaction owing to increase in vehicle weight, is usually overlooked.

Compaction of the subsoil destroys soil structure and has a negative impact on soil functions such as infiltration capacity, plant-available water, aeration and root penetration. This, in turn, adversely affects crop yields and the environment (for example, greenhouse gas emissions, soil-borne diseases and runoff losses).

A global distribution map of subsoil compaction susceptibility showed that 20% of arable land is at risk for subsoil compaction. Meanwhile, risk of subsoil compaction has increased over the past six decades. It is advocated that future farm vehicles must be designed to avoid subsoil compaction.

Of interest is the sauropods paradox story. On one hand, sauropods must have compacted the subsoil due to their almost twice-greater weight per leg than the heaviest farm machinery; on the other hand, high productivity must have been maintained to feed these giants. The authors speculate that the patterns of sauropod foraging behaviour were constrained towards minimising subsoil compaction risk to support land productivity and sauropod mobility.

This study identified a relatively high risk of subsoil compaction in New Zealand. This aligns with other New Zealand case studies. However, the extent of subsoil compaction and its adverse impacts on the crop yield and the environment remain an important knowledge gap.

 

Last updated: 17 May 2022 11:22am
Declared conflicts of interest:
None declared.

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