Organic v. Conventional: The Yield Debate

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Recently the journal Nature published an article of some significance.  The article is a meta-analysis entitled “Comparing the yields of organic and conventional agriculture”, and was written by Verena Seufert, Navin Ramankutty, and Jonathan Foley.   Meta-analysis is a useful and increasingly common research method employed by scientists.  When conducting meta-analysis researchers aggregate dozens and sometimes hundreds of different published research studies to discern broader patterns in the area of study.  This approach is becomingly increasingly common in the fields of medicine, climate research, and ecology, to name a few.

Summary

What follows is a cliff-notes, bullet point summary of the research results.   According to the study, “Overall, organic yields are 25% lower than conventional…”, however “organic performance varies widely over crop types and species.”

  • Yields of organic fruits and oilseed crops show a small (-3% and -11% respectively), but not statistically significant, difference to conventional crops
  • Organic cereals and vegetables have significantly lower yields than conventional crops (-26% and -33% respectively)

Yield performance varies widely not just based on the crop being produced, but also based on the agro-ecological and socioeconomic conditions under which that crop is produced.

  • Organic crops perform better on weak-acidic to weak-alkaline soils (pH between 5.5 and 8.0), possibly related to phosphorous being less available under acidic or alkaline conditions.
  • Organic performance is -35% under irrigated conditions, but only -17% under rain-fed conditions.
  • In developed countries organic performance is, on average, -20% whereas in developing countries it is -43%.

In summary, “Organic agriculture performs better under certain agroecological conditions – for example organic legumes or perennials, on weak-acidic or weak-alkaline soils, in rainfed conditions, achieve yields that are only 5% lower than conventional yields.”

Management also plays a critical role:

  • Having applied best management practices show better organic performance…organic yields thus depend more on knowledge and good management practices than conventional yields.
  • Organic yields are low in the first years after conversion and gradually increase over time, owing to improvements in soil fertility and management skills.

The improved management associated with organic agriculture also contributes to farm resilience, which can make a tremendous difference in relation to climate-related risk.  As the paper notes: “Soils managed with organic methods have shown better water holding capacity and water infiltration rates and have produced higher yields than conventional systems under drought conditions and excessive rainfall.”

Analysis

Some articles on the Internet have used this research to question the future viability of organic agriculture.  In particular, Time magazine’s “Ecocentric” blog published a post with the title “Why Organic Agriculture May Not Be So Sustainable.”  The article alludes to a criticism of organic agriculture cited by the Nature researchers: “Critics argue that organic agriculture may have lower yields and would therefore need more land to produce the same amount of food as conventional farms, resulting in more widespread deforestation and biodiversity loss, and thus undermining the environmental benefits of organic practices.”

What I found significant about the Nature article was not, however, the fact that organic yields are overall lower, but in fact how closely comparable those yields are under relatively difficult circumstances.  As the researchers note, “Organic systems may rival conventional yields in some cases…”  Consider the following facts:

  • Most agricultural subsidies are structured to favor large agribusiness, hence putting small-scale organic producers at an economic disadvantage, thereby negatively affecting capital inflows and technological innovation
  • 50 years of research at US land-grant institutions have focused on conventional, chemically-intensive agriculture.  In fact, the US has fallen behind countries like Austria, Switzerland, and Germany in leading-edge research in organic agriculture, adding another structural advantage for conventional agriculture.
  • The research did not distinguish between industrial and small-scale organics.  The former is characterized by scale, efficiency, and mechanization, allowing more land to be worked per unit of labor.  The latter is characterized by high-yield polycultures where more labor and management is required per unit of land, but overall farm yields can be much higher.

In this context, the comparison of organic to conventional becomes much more favorable and impressive, and illustrates that organics could indeed compete with, and perhaps could surpass conventional agriculture under the appropriate circumstances.

From a yield perspective, perhaps the real disadvantage to the organic producers, and the single most important factor accounting for the -25% differential, is the prohibition of nitrogen fertilizers.  Indeed, as the authors note: “Organic systems appear to be N limited, whereas conventional systems are not.  N availability has been found to be a major yield-limiting factor in many organic systems.”   The prohibition of chemical fertilizers in organic systems is understandable, considering the irresponsible and ecologically disastrous problems of nitrogen saturation and aquatic eutrophication (Google both for more information).

My attitude towards chemical fertilizers is more nuanced.  Surely saturating soils with NPK mixtures through chemical injections and sprays is unwise, but not being able to responsibly apply small to moderate amounts of chemical fertilizers in the appropriate context is a big setback for the sustainable agriculture movement.  And while nuanced views won’t change the mandates of organic labeling, I certainly think we should be rethinking our attitude towards chemical fertilizers in general.  If organic labeling had allowed for judicious and limited use of nitrogen fertilizer, perhaps the -25% differential would be much less, or even non-existent.  Additionally, nitrogen fertilizer can be produced sustainably from hydro or wind power (see freedomfertilizer.com).

Closing the yield gap between organic and conventional agriculture is a big challenge.  As we have seen, lower yields in organic agricultural systems are primarily a function of human management, structural problems, and socioeconomic constraints.  The challenges on the production side, while significant, could be easily surmounted given sufficient attention and resources.  One factor that is sure to contribute to further success is the continued education of farmers and ranchers, an area where HMI focuses a great deal of our time and energy.

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