Soil Compaction in Alfalfa Fields Ronald T. Schuler, Professor Extension Agricultural Engineer Biological Systems Engineering University of Wisconsin- Madison

Soil Compaction Causes include combinations of:  Wheel Traffic  Tillage  Precipitation Types  Surface  Subsoil

Loam soil by volume Non-compactedCompacted

Compaction Issues Tires  Size  Inflation pressure  Tire design, radial vs. bias Machinery  Avoid wet soil  Wheel alignment  Machine selection  Machine weight

Compaction Issues Tires  Size  Inflation pressure  Tire design, radial vs. bias Machinery  Avoid wet soil  Wheel alignment  Machine selection  Machine weight

Contact Area-Size-Diameter (Firestone) TireSizeTire Dia.Area(in 2 ) Radial Tires Flat3”Sinkage 18.4R R R R Bias Tires

Contact Area-Size-Width (Firestone) TireSizeTire WidthArea(in 2 ) Radial Tires Flat3”Sinkage 16.9R R R Bias Tires

Compaction Issues Tires  Size  Inflation pressure  Tire design, radial vs. bias Machinery  Avoid wet soil  Wheel alignment  Machine selection  Machine weight

6 psi 18 psi Impact of Tire Pressure

Inflation pressure-slight tire bulge with the proper pressure on radial ply tires 18 psi 6 psi Bulge

Top View: Measured soil-tire interface stress (psi) distribution of an 18.4R38 tire

Compaction Issues Tires  Size  Inflation pressure  Tire design, radial vs. bias ply Machinery  Avoid wet soil  Wheel alignment  Machine selection  Machine weight

Radial vs. Bias Ply Tires Contact Area

At Proper Inflation Pressure, Radials have greater Contact Area

Tractor Manufacturer Recommendations Tire Size – Pressures-psi Axle Load (lbs) Radial Bias

Compaction Issues Tires  Size  Inflation pressure  Tire design, radial vs. bias Machinery  Avoid wet soil  Wheel alignment  Machine selection  Machine weight

Impact of soil moisture on compaction (depth and sinkage) Hard dry soilNormal Wet soil Depth, In.

Compaction Issues Tires  Size  Inflation pressure  Tire design, radial vs. bias Machinery  Avoid wet soil  Wheel alignment  Machine selection  Machine weight

Wheels should follow in same track Wheel alignment-harvester and wagon

Wheel alignment- tractor and wagon

Small Square Baler-Bottom Feed Wheels aligned-tractor, baler and wagon

Mid-Size Rectangular Baler Wheels aligned-tractor and baler

Compaction Issues Tires  Size  Inflation pressure  Tire design, radial vs. bias Machinery  Avoid wet soil  Wheel alignment  Machine selection  Machine weight

Sickle Cutterbar-Roll Conditioner 14-foot width

Self-propelled mower-conditioner

Front self unloading wagon

Wheel Alignment –harvester and wagon

Dual rake merging two windrows

Merger - Picks up one windrow and places it on the adjacent one

Merging three windrows into one

1 Mower-conditioner-pull or self-propelled 2 Mower conditioner width, feet 3 Rake-to rake, merge or do not rake two windrows together 4 Area covered by wheel traffic if uniformly distributed 5 T-M/A – ton miles per acre System Comparisons-three cuttings per year Type 1 Width 2 (ft) Rake 3 Area 4 T-M/A 5 Pull13None Pull16None Pull13Rake Pull16Rake Self-Prop16Rake Self-Prop16Merge Pull13Merge Self-Prop13Merge(Dbl) Self-Prop16Merge(Dbl) 2.332

Compaction Issues Tires  Size  Inflation pressure  Tire design, radial vs. bias Machinery  Avoid wet soil  Wheel alignment  Machine selection  Machine weight

Tractor ballasting criteria Towed Load wt. vs.Max.Speed Towing machine wt.mph 1 to to 110 More than 2 to 1Do not tow

Concluding Remarks  Select appropriate tire  Use proper tire pressure  Align wheels  Reduce traffic of large equipment  Use safe towing machine weight

The End