Good Soil Structure

Why organic soil matter is important

In well developed fertiliser grassland soils there is typically 50 to 100 tonnes of organic matter per hectare. It comes from all the organic matter being 'cycled' in the grassland system, that is dead herbage, dung, urine etc. and it accumulates in the soil where it of course has beneficial effects on the moisture holding ability and the biological activity in the soil. The application of fertiliser is absolutely essential for this accumulation of organic matter to occur. Starting with a virgin soil fertiliser applications stimulate plant growth thus ensuring sufficient animals can be grazed. Thus there is plenty of excreta and dead plant material in the system and hence soil organic matter accumulates.

The soil organic matter contains nitrogen, phosphorus and sulphur. Of the 50 to 100 tonne/ha or so of organic matter in a typical developed grassland soil there are approximately 4-20 tonnes of organic N and 1-4 tonnes of organic P and S.

The proportions of these nutrients in the organic form, relative to the amount present (ie. Organic plus inorganic), is about 90%, 95% for N,S and P respectively. In fact most of these ‘organic' nutrients came originally from fertiliser.

A further fraction of the soil organic matter is what is called microbial biomass. It is in effect a measure of the amount of organic matter tied up in the millions of microbes which live in the soil breaking down the organic debris and , so vital for a healthy soil. The size of the microbial biomass can be interpreted as a measure of the biological activity in the soil. (Dr D Edmeades).

Picture a well managed soil under long term pasture - a friable, well structured topsoil with high levels of organic matter, a mass of roots, and lots of earthworms. After cultivation the soil can become less friable. More cloddy, and organic matter and root mass can decline, earthworm numbers decrease, tillage pans can form, and erosion risk increases. Soil structure can decline to a state where crop yields are reduced and production costs increase. Also erosion may significantly reduce topsoil depth.

If you do not replenish nutrients and organic matter, and carefully time your tillage operation you may well be destroying your soil structure. Are you mining, maintaining or building your soil structure?

OSFLO contains 47% organic matter and when applied to crop ground at the recommended rate of 5000 kg per hectare makes a valuble contribution to the soils organic matter content.

Good soil structure is vital for growth

Having good soil structure is vital because it impacts the following:

  • Soil aeration
  • Transmission and storage of water
  • Soil temperature
  • Root penetration and development
  • Nutrient cycling
  • Resistance to structural degradation
  • Susceptibility to soil erosion

Good soil structure promotes:

  • Seed germination and emergence
  • High crop yields
  • Good crop quality

Good soil structure has many benefits including:

  • Increasing the window of opportunity for cultivating
  • Minimising tillage costs (tractor hours, number of passes, size of the tractor and implements required).

Soil organic matter is vital

Having good organic matter in your soil is vital for:

  • Improving soil health
  • Regulating biological, physical and chemical processes
  • Promoting infiltration and water retention
  • Developing and stabilising soil structure
  • Cushioning the impact of wheel traffic and cultivation
  • Reducing the potential for wind and water erosion
  • Containing and supplying plant nutrients and energy for organisms

Unfortunately culitvation reduces organic matter levels.
Pasture and no-till improve or maintain organic matter levels.
Crop residues and compost help build-up organic matter.

Low Organic matter levels can cause damage by:

  • Reducing soil fertility
  • Increasing nitrogen and phosphorus requirements
  • Enhancing leaching losses
  • Increasing dependency on fertiliser inputs
  • Increasing cultivation requirements
  • Increasing susceptibility to erosion