Climate Change, Agriculture, and Chloropicrin Soil Treatment

Climate change is a politically divisive topic.  However, it is advisable for those with a stake in agriculture to explore the ramifications of potential weather changes on business.  As weather instabilities or weather extremes become more common, farming will need to change. 

One common refrain regarding climate change is that existing agriculture will move to latitudes with favorable growing conditions i.e. the US corn belt moves to Manitoba and Saskatchewan. However, the added heat and water vapor at the heart of climate change is predicted to drive not just a change in temperature but an increase in unstable weather patterns. Agriculture likes stable, predictable weather patterns. 

Weather uncertainties will drive production of higher value crops more and more toward out-of-soil, protected agricultural systems.  The economics of switching to protected agriculture will become increasingly favorable as weather patterns shift or become less predictable. Traditional high-value markets for chloropicrin will be replaced increasingly quickly by out-of-soil production systems. 

The bulk of chloropicrin’s future use lies, therefore, in crops not easily scaled to protected agriculture systems.  These are crops generally recognized as agronomic crops. 

A few broad impacts of chloropicrin on the drivers of climate change – carbon production and removal – associated with agronomic crop production can be envisioned. 

  1. Crop Production Efficiencies. Chloropicrin use increases crop production efficiencies. This means that the use of chloropicrin allows for production of more food on less land.  This occurs through the reduction of pests and because of positive changes in soil microbiology. The former concept is understood well. The role of the latter concept is beginning to be realized. The use of chloropicrin reduces the overall demand on agricultural resources (land, soil, nutrients, water, fuel, etc.) which, in turn, reduces the production of the greenhouse gases associated with agricultural production.  Value of a few of these benefits have been calculated in the potato crop at the farm level but more could be done to understand the impact of improved production efficiencies at the societal level.  An understanding of the impact of chloropicrin on other agronomic, non-traditional use crops needs to be developed.
  2. Land/Soil Use. Where adopted in potato production in colder climates, chloropicrin has improved soil sustainability. For instance, traditionally, the winter prior to planting potatoes, potato fields in the US and Canada are left fallow or bare. Potato fields can easily be planted early in the spring as soon as soil temperatures are appropriate. Bare, unprotected soil, however, has a higher risk of erosion over the winter and spring. Raised row application of chloropicrin in the fall and establishment of an overwintering cover crop to stabilize the application, also stabilizes and protects the soil. The chloropicrin potato production system reduces tillage passes, saving inputs.  Chloropicrin can push potato production into a system with less soil erosion making production more sustainable under more erratic weather conditions.  A healthier soil is a more productive soil.  This is a direct link between chloropicrin use and improved soil sustainability in a major agronomic crop. 
  3. Carbon Storage in the Soil.  In Europe and other parts of the world, the idea that farm fields could act as large carbon sinks is gaining traction. The plan is to grow large amounts of cover crops, turn the crops into the soil, and store the carbon-laden biomass underground in a way that it is slowly digested. This idea is not without some criticism.  

Based on recent chloropicrin soil health studies, a possible method that utilizes chloropicrin may be available to store large amounts of carbon in soil.  Following soil treatment with chloropicrin, total microbial biomass increases relative to non-treated fields.  Could carbon be “stored” in soil in the increased microbe population?  Data suggests that up to half of soil organic matter is made of dead soil microbes. Carbon stored in dead microbes is kept out of the atmosphere longer than some other forms of organic carbon.  It has been suggested that land managers should move to production systems that promote soil microbial growth. The microbes will consequently die and help store carbon in the soil, which could help minimize self-reinforcing cycles under climate change.  Chloropicrin could play an important role in managing storage of carbon in soil through the promotion of growth and death of soil microbes.

The key to thinking about chloropicrin in agriculture as it relates to climate change is to move beyond thinking of chloropicrin solely as a pesticide. Chloropicrin use is a foundational agricultural choice that ripples positive benefits from the farm through the larger society. We need to document both the on-farm and societal benefits associated with chloropicrin use and speak to them.  The future role of chloropicrin in agriculture could be significantly different than the role it plays today.  The new role of chloropicrin will not happen without new thinking and effort.