Soil organic matter and cultivation costs

  • Soil “crumbs” are held together by a protein made by soil micro-organisms.
  • Reducing cultivations reduces oxidation of soil organic matter.

Bill Butterworth 10 October 15

Mycorrhiza 1P1000825

Mycorrhiza 1P1000825

Look carefully at the white bit in the center of the picture. Under the right conditins during tillage, mycorrhiza may just be visible to the human eye.

Some years ago there was a breakthrough in identifying soil “glue” and its relationship to soil crumb structure, soil tilth, gas exchange, soil water movement and retention, crop stress and disease. Researchers at the Soil Microbial Systems Laboratory, Beltsville, US Department of Agriculture (USDA), identified a protein which they named “Glomalin” which appears to be the glue which holds soil aggregates together. The protein is made by soil fungi (called mycorrhiza) which feed on organic matter. This breakthrough can be coupled to advancing knowledge on mycorrhiza and can open up the route to lower costs in cultivations, lower costs in crop protection and higher crop yields.

Sara Wright, a microbiologist researcher at the USDA, was part of the team which identified and named “Glomalin” as the protein which appeared to be the binding agent in the formation of soil aggregates and, therefore, the controller of so many practical functions in which the operator in the field is so interested. The team found that tillage tends to lower Glomalin levels.  Some research carried out by myself for what was then ICI Plant Protection showed that conventional cultivations often reduced soil organic matter by 35 per cent per annum but “direct drilling” or zero till reduced this to less than 10 % (Also see “Reversing global warming for profit” by Bill Butterworth, published by MX Publishing.)

 Soil Aggregation

During the 1980’s, quite a bit of academic research was done on soil aggregation and the formation of crumb structure. It was clear then that cultivation increased the oxidation and mineralisation of organic matter which was closely related to the formation of aggregates.  In turn, it was also clear that such loss of aggregation also resulted in reduced gas exchange, reduced water movement, reduced crop growth and increased power requirement for cultivations. As many arable farmers know to their cost, the pressure to get on and do the job by putting power in (such as power harrows to “force” a seedbed) gets the operation onto a descending spiral of declining soil structure, pressure on yields and increased costs.

By the way, more than half of all the field cultivations in the USA are what they call “zero till”.  In the UK, we are a little more sophisticated in crop production and average twice the yield per ha.  However, it is clear that the power used to cultivate is not going to get cheaper and that means that reducing cultivation where sensible and protecting organic matter in the soil is of increasing interest.  Coupled to that, increasing soil organic matter by using composts must be part of the discussion – especially if you can get paid to take the materials to make the composts.