|
November 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.
 |
| Which
is the organic corn? You guessed it --
the corn on the left. This picture was taken in
1995, one of the six drought years covered in the
study published this September in the American Journal
of Alternative Agriculture. |
|
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 crop systems.
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 CNV corn.
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.
|
 |
Maize
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 conditions, too. |
|
|
“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 zone.
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. 
|
