7, 2003: Imagine the press that would be generated
if the genetic engineering industry developed a transferable gene
that would allow crops to yield 35% to 100% more under drought conditions.
Every newspaper would feature the story on its front page and it
would be on prime time TV. Well, the organic “industry”,
a.k.a. organic farmers and researchers, has done the equivalent,
not via genetic engineering, but by developing a soil-plant system
that numerous studies have shown gives crop yields that under drought
conditions are commonly 100% higher than comparable conventionally
managed crop systems.
A paper by Rodale Institute® researchers, published in the
September 2003 issue of the American Journal of Alternative Agriculture,
describes not only how the organic system gives better yields of
corn and soybeans under severe drought conditions, but also shows
how the organic system gives better environmental stability under
flood conditions, by allowing less runoff and harvesting more water
for groundwater recharge.
The paper, “The performance of organic and conventional cropping
systems in an extreme climate year”, by Don Lotter, Rita Seidel,
and Bill Liebhardt, looked at data from The Rodale Institute’s
Farming Systems Trial® (FST) during the climatically unique
year 1999. The year was unique because it was characterized by a
severe crop season drought, followed by a hurricane-driven torrential
rainstorm in mid-September. The results also showed substantial
differences between two different organic crop management systems,
one based on manure for fertility, and the other based on legume
green manure crops.
The Rodale Institute’s Farming Systems Trial has run continuously
since 1981 and is one of the longest running crop sustainability
comparison experiments in the world. The 1981-2002 phase of the
FST (a new phase has recently been initiated) compared corn and
soybean crop performance in two organic treatments, one of them
manure-based (MNR), and one legume-based (LEG), with a conventional
treatment (CNV). The MNR treatment was a five-year corn-soybean-wheat-clover/hay
rotation; the LEG a corn-soybean-wheat-green manure rotation; and
the CNV a five-year corn-corn-soybean-corn-soybean rotation. Herbicides
and synthetic fertilizers were the main inputs into the CNV treatment.
Each replicated plot had a lysimeter underneath the plow layer,
essentially a water collecting device, so that water could be collected
for a half meter square of each of the 80 foot long plots. Water
was pumped out of the lysimeters at intervals and the amount measured.
The plots were replicated in such a way that in most years, all
three treatments had corn and soybean crops to compare.
The authors start by showing that in five out of six of the drought
years during the 21-year experiment, corn yields were significantly
higher in the organic treatments than those in the conventional
treatment. The 1999 drought year being far more severe, results
were more complex, and showed differences between the two organic
Rainfall during the 1999 crop season totaled only 41% of average.
The critical month of July had only 15 mm of rain, about 17% of
the average. Crop yields were reduced to less than 20% in corn and
60% in soybean. Most farmers would have abandoned such a dismal
corn crop; however, this kind of stress can expose differences between
crop management systems that mild stress conditions cannot.
Yields in 1999 in three out of four cases were at least one third
higher in the organic treatments than in the CNV. Corn in the MNR
treatment yielded 50% higher than CNV corn, and soybeans in the
MNR and LEG treatments yielded 35% and 96% higher than CNV, respectively.
The fourth case was the exception: LEG corn yielded 66% lower than
Why did LEG corn fare so poorly – yielding one third of CNV
corn, while the other organic treatments in both crops yielded at
least one third higher than CNV? This, the authors explain, has
to do with the nuanced nature of organic crop management. In the
LEG case, hairy vetch, sown in the fall of 1998, grew to near record
biomass because conditions in fall and spring were ideal for its
growth that year. By the time the vetch was disked under in late
April, it had used up what turned out to be most of the water that
crops would get that year, which is normally stored in the soil.
Additionally, the spring conditions were such that tillage for weed
control in the LEG treatment was inadequate, and weed biomass was
double that of the MNR treatment. The MNR had a clover cover crop,
which had much less biomass and took less water.
and soybean grain yields in conventional (CNV), legume
based (LEG) and manure based (MNR) plots, 1999.
The higher yields in the organic treatments are believed to be
due to the higher water holding capacity of soils in the organic
treatments. Better colonization of roots by beneficial mycorrhizal
fungi in organic crops may also play a role, since mycorrhyzae have
been shown to help a plant scavenge water from dry soils with their
extensive network of hyphae.
Soil water held in the crop root zone was measured and shown to
be consistently higher by a statistically significant margin in
the organic plots than the conventional plots, due to the higher
organic matter content in the organic treated soils.
Water captured below the root zone in the lysimeters provided evidence
of the water capture characteristics of the three crop systems.
Over a five year period, water collected by the organic plots was
about 20% higher than the CNV plots, indicating that groundwater
recharge is better in the organic system, and that runoff (and concomitant
potential for flooding and erosion) is lower.
The exceptional water capture capability of the organic treatments
stood out during the torrential downpours during hurricane Floyd
in September of 1999. The organic systems captured about twice as
much water as the CNV treatment during that two day event
The authors show a graph of monthly water capture during the 1999
season and point out an interesting fact. In May, when crops were
only a few inches high, water “capture” by lysimeters
in the CNV plots was one third higher than the organic treatments
– the only month in which lysimeter water was higher in the
CNV plots than in the organic treatments.
|Organic fields capture water better in flood
“Capture” is not the right word for water that percoloates
into the lysimeters during a water scarce month, however, because
really what was happening, say the authors, is that water was retained
by the root-zone soil in the organic treatments, and did not percolate
down to the lysimeters. The water retained in the root zone of the
organic plots could be used by the crops for growth. Therefore,
the true “capture” of water was occurring in the organic
plots, and loss was occurring in the CNV treatment. This is offered
as additional evidence of the mechanism of drought resistance of
the organic treatments – the retention of water in the root
Given that we are entering an era of extreme climate fluctuations
and global climate change, the research described here by the Rodale
researchers is important. There is great need to develop food production
systems that are adapted to climate conditions that are characterized
by increased drought and flood. Organic and other crop management
strategies that optimize soil organic matter, biological diversity,
and crop robustness, should be our first line of defense.