Effects of soil compaction on grain yield of wheat depend on weather conditions

The use of heavy farm machinery has resulted in widespread soil compaction in many regions of the world. Compacted soil limits the access of crops to soil water and nutrients and is expected to reduce crop productivity, but the influence of weather conditions on the interactions between compacted soil and crop productivity is unclear. Furthermore, early vigor has been regarded as a promising trait for improving the yield of crops grown under edaphic stress such as soil compaction. We aimed to assess the combined effects of soil compaction and contrasting weather conditions on growth and grain yield of spring wheat, and to evaluate the association between early vigor and grain yield under temporal variations of the soil physical conditions. Nine spring wheat genotypes were grown on compacted and non-compacted soils during two cropping seasons with contrasting weather conditions in Central Sweden. Compared to the non-compacted treatment, soil compaction increased the relative growth rate of shoot biomass from sowing to stem elongation, and from stem elongation to flowering in the drier year (2018), but decreased the same traits in the wetter year (2019). The contrasting effects of soil compaction on shoot growth in the two years could be explained by soil moisture and penetration resistance associated with the interactive effects of soil compaction and weather condition. Higher early vigor, here indicated by higher relative growth rate from sowing to stem elongation, was associated with reduced grain yield under the progressively drying and hardening soil conditions during the entire cropping season of both years. We conclude that the interactive effects of soil physical and weather conditions need to be considered when evaluating the impact of soil compaction on crop growth and productivity. The potential of early vigor to increase grain yield is strongly influenced by the temporal dynamics of soil physical conditions.