PLoS One. 2016; 11(8): e0161673.
Published online 2016 Aug 23. doi: 10.1371/journal.pone.0161673
PMCID: PMC4995028
Anil Shrestha, Editor
Abstract
Land
area devoted to organic agriculture has increased steadily over the
last 20 years in the United States, and elsewhere around the world. A
primary criticism of organic agriculture is lower yield compared to
non-organic systems. Previous analyses documenting the yield deficiency
in organic production have relied mostly on data generated under
experimental conditions, but these studies do not necessarily reflect
the full range of innovation or practical limitations that are part of
commercial agriculture. The analysis we present here offers a new
perspective, based on organic yield data collected from over 10,000
organic farmers representing nearly 800,000 hectares of organic
farmland. We used publicly available data from the United States
Department of Agriculture to estimate yield differences between organic
and conventional production methods for the 2014 production year.
Similar to previous work, organic crop yields in our analysis were lower
than conventional crop yields for most crops. Averaged across all
crops, organic yield averaged 80% of conventional yield. However,
several crops had no significant difference in yields between organic
and conventional production, and organic yields surpassed conventional
yields for some hay crops. The organic to conventional yield ratio
varied widely among crops, and in some cases, among locations within a
crop. For soybean (Glycine max) and potato (Solanum tuberosum),
organic yield was more similar to conventional yield in states where
conventional yield was greatest. The opposite trend was observed for
barley (Hordeum vulgare), wheat (Triticum aestevum), and hay crops, however, suggesting the geographical yield potential has an inconsistent effect on the organic yield gap.
Introduction
Certified
organic agricultural production area in the United States has increased
steadily since the inception of the 1990 Organic Foods Production Act.
Advantages of organic agriculture include economic benefits for
producers [1] and increased provision of ecosystem services such as biological pest control and biodiversity conservation [2–4].
Sociocultural benefits such as quality of life for farming communities
have been theorized, but research in this area of organic agriculture is
limited [5].
One
of the main criticisms of organic agriculture has consistently been
lower crop yield compared to non-organic systems. Meta-analyses
comparing yields of organic and conventionally grown crops have
repeatedly demonstrated a yield gap between the two systems. Recently
published meta-analyses report mean estimates across all crops varying
from 19% to 25% lower yields in organic systems [6–8].
Critics of organic agriculture argue that society cannot justify being
less efficient with arable land in the face of a rapidly growing human
population. With respect to conservation interests, if more-efficient
conventional farmers can match organic yields with 70% of the land,
remaining land could be set aside for conservation and other
environmental benefits [9–12].
However, yield gains have not been clearly linked with increased land
set aside for conservation at the global or regional scale, thus the
yield/conservation tradeoff is likely a false dichotomy not
representative of the socioecological complexity of agricultural
systems, with management decisions tied to markets and policy [13].
Yield
differences between organic and conventional production vary with crop
type and management practices. In their analysis of organic studies
conducted world-wide, Seufert et al. [8]
reported smaller yield gaps for organic fruit (3% lower than
conventional) and oilseed crops (11% lower than conventional) and large
gaps for organic cereals and vegetables (26% and 33% respectively). When
studies were partitioned by plant type, organic legumes and perennials
had more competitive yields than non-legumes and annuals, likely a
result of more efficient nitrogen use by plants [8].
Meta-analyses
of the published literature do not necessarily reflect the full range
of innovation or practical limitations that are part of real-world
commercial agriculture. Agricultural research, by necessity, often takes
a reductionist approach in order to best isolate and quantify the
effect of interest [14].
Additionally, equipment, labor availability, and scale of production is
typically much different between research and commercial production.
Although these differences may not necessarily bias yield differences
between systems in any systematic way, there is always value in
comparing estimates from controlled research with commercial production
data. The analysis we present offers a new perspective, based on organic
and conventional yield data reported to the United States Department of
Agriculture (USDA) as part of their 2014 organic and agricultural
producer surveys. The USDA data is a window into the range of farming
operations and the best available measure of how the different
production systems perform in a practical sense. USDA has made area and
yield of organic and conventional crops, summarized at the state level,
available to the public. Although this data set provides only a snapshot
of agricultural production in the United States from one growing
season, it represents actual commercial production rather than estimates
from research studies. Data from field research stations and commercial
farms are complementary, each with their own strengths and weaknesses [14].
The USDA survey data provides an opportunity to compare the findings of
factorial research experiments with reported production yields. This
rich data set offers yield comparisons from a diversity of crops and
states, representing the breadth of organic and conventional
agricultural production in the United States.
