Zero and controlled traffic improved soil physical conditions and soybean yield under no-tillage

Soil compaction can negatively affect a range of soil hydraulic, biogeochemical and plant physiological processes. A study conducted in Luj ' an (Argentina) investigated the effect of three traffic treatments (zero, controlled, and random traffic) on soil physical properties and soybean yield over a period of eight years. The soil at the site (Typic Argiudoll) had been managed under continuous no-tillage for nine years. Field-wheeled areas under controlled and random traffic management were 3309 m2 ha- 1 or 33.1% and 4622 m2 ha- 1 or 46.2%, respectively. 'Random', non-controlled traffic farming represented the standard mechanisation management practice. The three traffic treatments relied on commercially available (unmodified) farm equipment. Results showed that soil cone Index (depth range: 0-450 mm) increased in the order: zero (1.90 +/- 0.31 MPa) > controlled (2.46 +/- 0.19 MPa) > random (3.75 +/- 0.21 MPa) traffic, respectively, which therefore explained treatment differences in root biomass. Water infiltration rates decreased significantly with increased traffic footprint (by up to 35% in random traffic), which therefore reduced plant available water and influenced crop performance. Grain yields with zero traffic were fairly consistent between-years, but increased with controlled traffic (which progressively approached the yields achieved with zero traffic) and decreased in random traffic at average rates of 33 and 29 kg ha- 1 per year, respectively. Treatment differences in grain yield widened in drier compared with wetter years when plant growth and yield were less constrained by water availability. An average yield penalty of approximate to 30% was recorded in random traffic relative to the other treatments. Gross income with random traffic was USD787 per ha, which compared to USD1179 and USD1116 per ha with zero and controlled traffic, respectively. The proposed approaches to mitigating adverse effects of compaction on crop productivity, sustainability and profitability appear to be cost-effective options and may be adopted when fully-matched machinery is not available. There is potential for future development of controlled traffic farming in Argentina.