Improving soil structure

Farming can cause clay to physically degrade

The physical properties of clay soils degrade when sodium (Na) and to a lesser extent magnesium (Mg), displace calcium (Ca).  Na and Mg form weaker bonds between the clay platelets (very small, flat minerals) than those formed by calcium.

Good soil structure

Platelets bonded in aggregates with large pore spaces

Poor soil structure

Platelets dispersed with no pore spaces

Cultivation breaks these weakened Na and Mg bonds, causing the clumps of platelets (aggregates) to disintegrate into individual platelets. The loose platelets disperse into a suspension then settle and fill air spaces in the soil.  This results in:

Poor drainage

Reduced aeration

Water logged surface

Slippery boggy conditions

Loss of surface nutrients

Surface crusting

Water stress in the ripening period

Solid, hard surface when dry

Difficult cultivation

Increased fuel usage cultivating

Poor weed control

Greater surface runoff

Physically degraded clays yield less because of

Difficult cultivation leads to less timely sowing

Cloggy sead beds reduce germination

Surface curst prevents emergence

Compaced, waterlogged clay with poor aeration reduces root growth

Weed control is less effective

Less water infiltrates soils, increasing water stress and early burning off

Subclover is unable to bury seed resulting in poor regeneration

Gypsum improves soil structure by providing calcium that displaces some of the sodium and magnesium.  Calcium increases the strength of the bonds between the clay platelets.  This allows platelets to aggregate together into crumbs forming soft, friable, well draining soil.

Gypsum improves yields and profit through

Improved soil structure allows crops to get the best start, growth and finish

Less fuel is used during cultivation

Weeds germinate more evenly with stronger growth making herbicides more effective

Crops are healthier and are able to compete more vigorously against weeds

Better weed control by being able to travel across the paddock to spray at appropriate times