The influence of soil compaction and conservation tillage on sunflower’s (Helianthus annuus L.) below ground system

Soil compaction represents an important issue in theactual context of agricultural system sustainability. Research on thevarious developments of root systems under tillage has been exploredfor many crops, whether for the biomass area or the underground,but very little concerns Sunflower ( Helianthus annuus L.). The objectivesof the study were to understand the impact of soil tillage andof the induced mechanically compacted soil on: i) sunflower’s rootsystem architecture, ii) biomass area iii) production. Two complementaryexperiments were realized in the south of France (France’smain sunflower production area). In both experiments, increased resistanceof the soil to penetration was observed, characterizing soilcompaction. Under compacted soil, major changes in the sunflower’sroot architecture occurred (-55% of root length, -67% of root surface,and -42% of root diameter) and root system exploration was negativelyimpacted (assessed through the use of semivariogram). Thisresulted in a decrease of deep root exploration and in an increasedlateral growth. Modifications of leaf surface, biomass, yield, and kernelcomponents were also reported. Those modifications were theconsequences of soil compaction, and suggest a compensatory effectunder such constraint.