Monday, March 2, 2015

Chemical Agricuture 202: Monoculture - Limited Crop Rotation

A monoculture is the human agricultural practice of growing a single species crop over a wide area and for many consecutive years. The most common monoculture is field corn, where millions of acres per year are grown and sometimes in the same place for many years.

At face value this would seem very efficient as specialized corn planting and harvesting equipment can allow one farmer to grow thousands of acres per year. However the monoculture has a dark side which we will explore in this post.

In the past major field crops were rotated with hay, legumes or small grains to both fix nitrogen and break the life cycles of insects, weeds and diseases. These were ecologically sound practices that most farmers followed. Today imperatives to diversify have been overwritten by economies of scale. The self-regulating mechanisms of the past such as species rotation and diversification are gone leaving a monoculture, which is a vulnerable agreocosystem dependent on a high level of chemical inputs.

When my father started farming, crop yields were dependent on internal inputs, recycling of crop residue, control mechanisms such as crop, rotation and local rainfall. This gave the farmer modest yields, but they were consistent. Instead of crop insurance, they grew different crops or varieties in a field over a season to protect against pests or anomalous weather. If we looked at what I described above as a system, we would find that the link between agriculture and ecology was good and the current problems of environmental degradation were much less.

In agriculture today, 40 years later, monocultures have expanded significantly on a world wide basis, through increased geographical expansion of farms dedicated to a single crop and production of this same crop year after year on the same land. Data shows that crop diversity is way down and concentration of crops is way up. Political and economic forces have lead to unprecedented levels of monoculture, which are encouraged by the ability to participate in international markets and economies of scale.

Enablers that allow these large monocultures to be possible were mechanization, new crop varieties and agricultural chemicals to fertilize crops, and control weeds and insects. This created a shift over several decades to farms that are larger and more specialized. They are also more capital intensive making it harder for new farmers to get started.

As a small organic farmer, when I register my crop acres at the soil conservation commission. We identify 20-30 different species of crops on 8 acres, which doesn't even take into account the dozens of varieties within each species or the fact that I might have 2-3 crops in a given space in the length of a season. This is annoying for the guy filling out the paper work for me because, no one else would grow more than one crop in this space, or perhaps hundreds or thousands of acres.

Here are some consequences of monoculture specialization:

  1. Large agricultural systems typically have a poor systems design with little thought to how soils, crops and animals interact.
  2. Inputs such as fertilizers, energy, water, residue or manure have become more open as opposed to more closed in a natural ecosystem. Geographical concentration of feedlots and urban usage makes it difficult to return manure to the land because there is too much generated in one area to move it to where it could be recycled.
  3. Pest pressures in monocultures are severe, as habitat for natural pest enemies have decreased and opportunities to break the pest cycle are fewer.
  4. We assume that farmer intervention and high levels of energy inputs that allow monocultures to be grown beyond their "natural ranges" can be sustained.
  5. The ability to sustain production relys on a continuous supply of innovative varieties to fight these issues rather than a rotation of many species on the same farm.
  6. Yields level off or decline because of a steady decline productive potential through unsustainable practices.

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