Diagnosing poor seedbed soil structure

Poor seedbed soil structure impedes a seedling's ability to reach the surface and increases the risk of waterlogging. For example; dense hard-setting heavy soils are dense and poorly structured throughout the soil profile; better-structured heavy soils where cultivation has degraded topsoil structure.

 

Poor germination in cloddy dispersive topsoil.
Long term cultivation effect on soil structure.
Gypsum can markedly improve yield in very wet or very dry years
Puddles that are "milky" from dispersed clay.

What to look for

    Paddock

  • Areas of crusted or dispersed soil with poor germination, and worse waterlogging after rain.
  • Puddles that are "milky" from dispersed clay.
  • Soil surface crusts that impede seedling emergence after wet dispersed soil dries.

    Plant

  • Normal germination but reduced emergence due to soil crusting, cloddiness or waterlogged seedbed.
  • Plants in very dense sodic or magnesic soils may have slower root and top growth.
  • Delayed flowering of affected plants.
  • Subsequent growth is normal unless there are subsoil constraints.

What else could it be

Condition Similarities Differences
Waterlogging, deep seeding and silly seedling
Can cause poor emergence and weak seedlings, and can be worsened by poor seedbed soil structure. Poor seedbed soil structure is mainly a problem in heavy soils when the topsoil is crusted or dispersed.

Where does it occur?

  • Naturally sodic or magnesic soils such as moort soil common in the Great Southern, Lakes and Jerramungup districts, wandoo or mallee soils that often occur below breakaways.
  • Many clay soils also have low organic matter levels and are readily degraded by cultivation.
  • Cultivation or trampling of wet soil by livestock before significant pasture growth degrades soil structure.
  • Heavy rain on unprotected soils can create a crust on poorly structured soil surface.

Management strategies

Spreading gypsum
Spreading gypsum
Minimum tillage
Minimum tillage
  • Management practices include: No-till crop establishment and improved stubble retention.
  • Increasing soil organic matter with residue retention, green or brown manuring, or pasture ley.
  • Gypsum and possibly lime application. Note that not all soils are responsive to gypsum and a response test is recommended.
  • Compaction control or prevention.
  • Loosening topsoil and subsoil in association with gypsum application and controlled traffic cropping (with or without raised beds).
  • Avoiding heavy grazing during early winter and maintain sufficient cover during summer.

Where to go for expert help

Page last updated: Friday, 17 April 2015 - 2:07pm