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Study
Examines Yield and Quality Potential of Organic Cotton
by
Martha Brown for "CA/AZ/TX COTTON" magazine, April
issue
With organic cotton often commanding twice
the price of its conventional counterpart, cotton growers
might be justifiably tempted to make the switch to organic
production. But what sorts of challenges will they face
in the process? How do yields, insect damage, and input
costs in organic systems compare to those in conventional
systems? And what type of markets can a grower expect for
their organic crop?
These are some of the questions a team of
growers and UC researchers set out to answer with a three-year
study comparing organic and conventional cotton fields in
the northern San Joaquin Valley. During the 1993-1995 study,
team members monitored pest and beneficial arthropod populations,
mapped plant growth, measured nutrient status and plant
density, and compared yields and lint quality.
The results, reported in California Agriculture
(Volume 53, #4, 1999), offer a good news/bad news picture
of organic production. The study found that while organic
cotton can lower a grower's materials costs, demand markedly
higher prices, and be grown successfully without chemical
pesticides, it may also generate higher weed control costs
and can prove difficult to defoliate with organic methods,
sometimes resulting in more variable color grades. And although
organic and conventional lint yields were not significantly
different during the initial study period, subsequent years
saw organic yields drop a quarter to a half bale lower than
those of conventional crops.
"The interest in eliminating insecticide use for the
organic system was farmer-driven to test the feasibility
of producing cotton organically. I was surprised to see
that it was feasible to produce cotton without insecticides
at all. Yet critical issues remain in weed control and crop
preparation," says the study's lead author Sean Swezey,
a specialist at the Center for Agroecology & Sustainable
Food Systems (CASFS) at UC Santa Cruz. Swezey was also recently
appointed director of the statewide UC Sustainable Agriculture
Research & Education Program.
Production systems compared
Swezey and post-graduate researcher Polly Goldman from the
CASFS, Ron Vargas of UC Cooperative Extension in Madera
County, and Ralph Jergens of New Era Farm Service compared
four conventionally managed fields to four organic cotton
fields managed by Claude and Linda Sheppard of C& M
Organic Enterprises, Inc. All of the fields in the study
were planted to the same variety ('San Joaquin Acala-Maxa').
Both the conventional and organic fields were
planted within the same initial 2-week period each year.
However, planting densities differed markedly, with 20,000-35,000
plants per acre in organic fields compared to 35,000 to
55,000 in conventional fields.
Organic fields were fertilized with a late-winter
application of 6 tons per acre composted chicken manure
supplemented with foliar nutrients during the growing season.
Conventional crops had a synthetic nitrogen fertilizer used
both at planting and during the growing season.
Other differences in the two systems included the year-end
use of a zinc sulfate application as a nutritional supplement
and potential harvest aid in the organic crop. In the spring,
insectary-reared green lacewing (Chrysoperla carnea) larvae
were released into the organic fields to help control spider
mites, lygus and aphids. The conventional crop was treated
with one to three in-season miticide and/or insecticide
sprays, as well as preemergence herbicides at planting,
and one growth regulator and two end-of-season defoliant
applications.
Although furrow irrigation schedules were
similar between management types, the organic grower used
alternate-row watering in early-season irrigation to help
control pest populations and conserve water.
Pest damage minimal,
quality differences noted
Despite higher number of lygus bug (Lygus hesperus) in the
organic fields, there was little effect on boll retention.
This may be due in part to the study's setting. "The
northern San Joaquin Valley has the advantage of extensive
alfalfa crops, which may act as a "sink" for lygus,
which appear to prefer alfalfa as a feeding site,"
says Swezey. In general the research team found no pest
impacts in the organic plots. Predatory insects, which overall
were more abundant in organic fields, may have kept pest
arthropod populations under control.
These findings have implications for cotton
growers throughout the region. "Whether or not they're
interested in organic production, growers with fields near
alfalfa plantings may be able to count on some degree of
lygus control if the alfalfa fields are managed properly,
that is they are harvested so that edge insectary strips
are maintained," says Swezey.
Maintaining naturally occurring populations
of beneficial insects by avoiding early-season sprays may
also help reduce insecticide inputs. In subsequent years
of the study, growers using IPM techniques in conventional
fields reduced their total annual insecticide/miticide usage
from 17,628 pounds to 1,244 pounds, according to figures
from the Sustainable Cotton Project.
Most cotton quality parameters - fiber length,
fiber strength, micronaire and leaf content - were similar
in the two treatments. However, when color grades from the
1994 crop were compared, grades were slightly lower for
the organically grown lint, although the quality difference
was small enough that organic bales were not discounted.
"The minor difference in color grades
and occasional incidence of spotting in the organic bales
points up one of our biggest challenges in organic crop
preparation," says Swezey. "We need to develop
a more effective system of desiccating and defoliating organic
cotton so that leaf matter doesn't stain the lint."
According to Swezey, such a system may include
variety selection, watering patterns, mid-season mechanical
topping, or a combination of these cultural controls with
organically acceptable spray materials.
The organic fertility treatment did not appear
to affect plant nutrient levels, as levels in both systems
were within the adequate range for most of the sampling
dates. Plant height, number of nodes and height-to-node
ratio (HNR) were the same in both the organic and conventional
treatments.
Researchers found that lower plant density
in the organic fields resulted in more outer-position (farther
from the mainstem) open bolls. This contrasts with the conventional
system, which had a higher number of first-position bolls.
The study also indicated that per-bale operational
costs of production can be higher in organic plots because
of labor costs generated by hand weeding. "Priority
needs to be placed on improved mechanical or rotation-based
weed control in organic cotton," says Swezey. "We've
tested a number of alternative technologies, including propane
flamers, aggressive in-row tillage, and rotation sequences,
but more attention needs to be given to weed control to
bring down production costs."
Yields differences documented
In 1993-1995, researchers found that yields did not differ
significantly between the two systems. Swezey notes that
in both 1994 and 1995, planting weather in Madera County
was irregular and there were low yields throughout the county
in 1995.
In 1996, the research program expanded into
a larger effort known as BASIC (Biological Agriculture Systems
in Cotton), sponsored in part by the Sustainable Cotton
Project. The BASIC study brought more growers into the project
and compared more fields in the region. This expanded study
found that organic yields in some years have been a quarter
to half bale less (about 2.2 bales per acre) than the countywide
averages for conventionally produced cotton in a normal
weather year.
Swezey is confident that this yield gap can
be narrowed as growers and researchers develop more effective
ways to control weeds and prepare organic crops for harvest.
"Building an organic cotton industry will require additional
resources for research and marketing if acreage is to expand
significantly," says Swezey.
Acreage numbers suggest that expansion is
already underway. According to Sandra Marquardt, coordinator
of the Organic Trade Association's Organic Fiber Council,
1999 organic cotton acreage increased by 75% over 1998 levels,
with Texas, New Mexico, and California growers leading the
way. This contrasts markedly with the climate in the mid
1990s, when lack of a guaranteed market prevented many growers
from making the switch to organic production, according
to Will Allen of the Sustainable Cotton Project.
"I feel we're on an upswing," says
Marquardt. "I think the major difference between where
we are now and where we were in 1995 is that we have a much
greater number and breadth of both small and large companies
that are interested in buying organic cotton."
Martha Brown, Center
for Agroecology & Sustainable Food Systems UC Santa
Cruz
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