Science of Sustainability- Long Term Effects of Cultivation.

Cultivation has been a tried and true practice for agriculture since its beginnings.  But in recent years we have begun to understand what the long term negative effects it can have on your soil.  The negatives are not little ones either and repairing them will take long term changes in how we conduct agriculture.  While there are many different consequences to much tillage I am just going to quickly gloss over three of the most common ones.      

Soil Compaction

Soil compaction occurs when soil is compressed under weight from either a machine or animal.  Now some compaction is a natural occurrence and it is remedied by natural methods.  But when you introduce tillage into the equation it alters the balance between the soil compacting forces and the   soil loosening forces.  Now if you have ever seen a garden after it is freshly tilled you will notice that the soil is light, fluffy and very loose.  This fluffy top layer however covers up what is happening beneath the tilled layer.  When an area is under constant tillage you can loosen the top part of the soil but beneath it will be forming a plow pan layer.

A plow pan is a layer of soil that gets super compacted from being constantly run over by heavy machinery or organisms, but is never loosened because it forms beyond the reach of the tillage equipment.  While this layer is beyond the reach of tillage equipment it is not beyond the reach of most roots.  Plants put roots down deep in search of water and nutrients and when they hit this layer they can't get through it.  This cuts them off from things that they need and this can really hurt plant success.        

Loss of Organic Matter

Cultivation is the primary driver behind the loss of soil organic matter.  The decay process is hindered in the soil by how much oxygen is available to microorganisms.  When the soil is cultivated oxygen floods into the system and stimulates the microorganisms to do what they do and that is break down organic matter.  What happens is the rapid consumption of the organic matter which then reduces soil health and also releases CO2 back into the atmosphere.  Through continuous cultivation you can destroy even the most fertile of soils and are then forced to supplement the soil with a growing amount of fossil fuels nutrients.      

Reduced Populations of Soil Organisms

How would you like it if a tornado, wildfire, earthquake, and a flood all hit your house at the same time.  It would ruin your day and that is in essence what we do to soil organisms every time we till the soil.  So in a traditional industrial agriculture operation that would be twice a year at the minimum.  You can imagine that this might effect how successful certain organisms are at surviving. The larger the organism the greater the impact that tillage has on them.  But the larger organisms like earthworms are critical in processing decaying organic matter and they also loosen and aerate the soil with their movements.  When you reduce the population of these little guys you are directly impacting how loose, friable and nutrient rich your soil is.

Their is a place for tillage in the garden or farm and should be a tool that you have available.  But by keeping in mind what the long term consequences are you may be able to do something to mitigate them. There are options out there like cover crops and mulching which can accomplish many of the same things that tillage does without the same problems.

Stay tuned for more Science of Sustainability topics.