Advantages of the one-wheeled tramline for multiple machinery widths method on sunflower (Helianthus annus L.) and maize (Zea mays L.) responses in the Argentinean Flat Pampas

•The one-wheeled tramline method was useful to reduce the trafficked area•Soil compaction by machinery traffic was measured through relative soil compaction•The effects of agricultural machinery traffic on yields varied with the crop•Crops yield were differently affected by relative soil compaction•Root growth was affected by sampling position and relative soil compaction. The “one-wheeled tramline” for multiple machinery widths (OWTL) method, which implies confining compaction to only one common permanent traffic lane (PTL) without changing wheel tracks of the machinery, has been proposed as first step to adopt the Controlled Traffic Farming system. The objective of this study was to evaluate how far the stress distribution, caused by repeated wheeling, affects maize and sunflower response in Argiudolls. The OWTL method was applied in two experimental sites, one cropped with maize (Aurelia site) and the other one with sunflower (Videla site). At each site, 9 plots were defined and one common PTL was established within each plot. Three compaction treatments were assigned to plots in a randomized complete block design with 3 replicates. The 3 compaction treatments were: T0: control, PTL with initial soil compaction defined for one pass of the planter equipment; T1: PTL compacted until the soil reached 2 MPa; T2: PTL compacted until the soil reached 4 MPa. Thereafter, the machinery traffic was restricted to the PTL. Fixed sampling positions were established in the PTL (from the centre to the outer edge) and in the permanent crop bed (PCB). After 18 months from the experiment begining, relative soil compaction (RSC) at the depth interval 0-100 and 100-200 mm, maize and sunflower yield, and sunflower root biomass (RB) were measured. Critical bulk density was 1.58 ± 0.03 Mg m-3 and 1.62 ± 0.05 at Aurelia and Videla sites. Significant differences of RSC between sampling positions were observed at both sites, whereas significant differences between compaction treatments were observed at Videla site. The higher RSC values were observed at the depth interval 100-200 mm in the PTL. The lower yields were observed in the centre of the PTL in T2. Contrasting the yield of maize and sunflower obtained in the PTL of T0 vs the average of T1 and T2, differences of 2751 and 848 kg ha-1 were observed. No yield differences were found for the same contrast in the PCB. Sunflower RB was reduced by 56% in the PTL, without differences between compaction treatments. The higher RB wa