Trade-off between agronomical and energetical performances during barley sowing varying adjustable parameters in a tractor-tire-tool system

Abstract

Soil compaction on seedbed, resulted from the traffic of a tractor-tire-tool system, alters soil structure and harmfully impacts crop production. Soil conservation during sowing operations and the optimization of energy consumption of tractor-tire-tool system, form the focus of the global agriculture policies and farmers under the energetical and the agroecological transitions. The present study aims to find a trade-off between the agronomical and the energetical performances, during a sowing operation of spring barley (Hordeum vulgare), varying adjustable parameters (controlled factors) in tractor-tire-tool system (i.e. tractor speed, axle load distribution, inflation pressure and soil working depth). The adjustable parameters have been chosen as to be adjustable by a regular tractor operator. The study was carried out on a silty loam soil (with an average soil gravimetric water content of 23.4%) located in Northern-France. The used tractor-tire-tool system consisted of a Four-Wheel Drive tractor (140 HP of power) equipped with 480/70 R28 front tires and 580/70 R38 rear tires, and hitched to an air seeder. Agronomical performance is evaluated via the conservation of soil physical properties, and via the success of the sowing operation. The energetical performance is evaluated via the optimization of energy consumption. The conservation of soil physical properties was assessed via soil bulk density (BD) and air permeability (ka). The success of the sowing operation was assessed via barley seedling, counting the emerged plants at one to two leaves stage, and crop yield. Energy consumption was assessed via the consumption of fuel per hectare. BD and ka were negatively correlated (ρ = −0.56 and p-value<0.001), but ka was significantly more influenced by the controlled factors and their combinations showing higher sensitivity of pore continuity to the structural disturbance than pore space. Crop seedling and yield were slightly influenced by the variation of the controlled factors and their combinations. All these agronomical indicators depended significantly on the combination between the four factors showed as single treatment. Fuel consumption decreased significantly with the equal load distribution and increased with tractor speed and soil working depth solely. Nonetheless, it showed higher dependence on the combinations between the factors. As a conclusion, soil physical properties could be conserved, better barley seedling and yield could be obtained, and energy consumption could be optimized by equally distributing the axle load, accelerating tractor at 14 km/h, working the soil at 10 cm of depth and inflating tires at 140 or 80 kPa of inflation pressure.