What impact does agricultural animal traction have on soil health? Preliminary experimentation in organic market gardening

Soil health is an important factor in preserving the ecological functions of the agrosystems while ensuring productivity. Organic market gardening systems present technical challenges (weed management) and significant compaction risks (multiple interventions, repeated passes and heavy irrigation). Compaction is one of the most serious forms of soil degradation, and animal traction could limit this phenomenon, which reduces water infiltration into the soil and disrupts biological communities (including micro-organisms), and animal traction could limit this phenomenon. We conducted a study on an organic market-garden farmer's farm to compare the effects of animal traction versus motorized traction operations on soil health over a season of potato cultivation, using various physical (compaction, aggregation), hydrophysical (infiltrability) and biological (biomass and microbial activity) parameters. The results of the three sampling and measurement campaigns carried out on the passage areas (tractor wheel or horse hoof) clearly differentiate the two practices, with the animal traction characterized by a higher microbial biomass, soil aggregation and infiltrability. We have thus observed a negative correlation between the number of passes under motorized traction and soil microbial biomass, while there is no correlation with the passes’ number under animal traction. Moreover, the third campaign results, integrating measurements on passages and ridges, showed effects from the first season of differentiation of the technical itineraries, with a greater difference in penetrometry, bulk density and infiltrability between passages and ridges under motorized traction compared to animal traction operations. Finally, infiltrability was not only faster but more variable on the animal traction passages, whereas it was weaker and more homogeneous along the motorized traction passages. • Measured the effects of animal traction compared with motorized one on soil health. • Selected indicators to assess physical, hydrophysical and biological parameters. • Greater microbial biomass and more cohesive aggregates in animal traction. • Faster and more variable infiltrability in horse’s hooves passage zone. • Systematically slower infiltration in tractor’s wheel passage zone.