Thank you for your comments and help. I have pasted the responses I received
below. Some of these were sent via sanet but not all. I will keep you posted on
any useful results to emerge from our work - Geoff.
It is becoming obvious to me that it is the integration of livestock into the
that will more easily allow organic production. A portion of the farm in
for organic milk will easily get rid of your perreniel weed problems. My pigs
do a good job of
getting rid of perrenials such as quack grass.
Diversification of the farms would be the best chance of reducing serious weed
problems. Get some hay and pasture in the rotation. And even some vegtables.
Most weeds aren't a problem in
management intensive grazing. They are food. The grass will build organic
matter and the clovers will add nitrogen.
For the record, I'm not an organic producer. I'm getting closer every day.
The successful farms
before chemicals should be good models. Very very few were succesful without
extreme diversification and a huge livestock/pasture component.
I'm an ARS researcher with long-term research underway in organic grain
I'm collaborating with a weed ecologist on some of the issues that you
raise. We have 2 years of data to date.
I'll be very interested to see what kinds of responses you get to your
query. I think that there very little authoritative research information
available to answer your questions.
Lead Scientist, Farming Systems Project
Beltsville Agriculture Research Center
Beltsville, MD USA
Geoff: surprised that perennial weeds are such a problem. I helped
out with a study conducted in Ag Econ and Bus, involving a comparison
of organic and conventional dairy farming. My interest was the
agronomic aspects. Weeds were not perceived to be a problem by
organic producers, at all. Their rotations were dominated by
small grains (spring and winter) and forages (all types, including
hairy vetch and other winter annuals through to permanent grass
sods), with very little corn, soybeans, or other crops. Almost
everything grown was home-fed, with little in the way of either crop
sale or purchased feedstuffs.
About the only weed control that was intentionally included, apart
from strategic crop rotation and timely cultivation was the periodic
growing of fall rye in the crop rotation. The timing of growth of
rye in the spring coincides with that of quackgrass - their main
perennial weed - and is used to outcompete and suppress the quack.
I can share with you a very specific example of an organic approach to weed
management. When growing broccoli and cauliflower, I had a lot of
chickweed. During the peak of the growing season, we weren't able to keep
up with it and let parts of the field go. As it turned out, the broccoli
plants quickly outgrew the chickweed and we soon had a closed canopy. We
had MORE weed problems in the areas where we had cleaned the chickweed out.
After that, we allowed the chickweed to grow as part of our management for
those crops, and it worked quite well. A few years later I met another
grower who had discovered the exact same thing. There are some catches,
however. We had to start with good sized transplants in the field to make
sure the crop would beat the chickweed. I don't think it will work with
direct seeding, but I never tried, either. Also, careful consideration must
be given to crop rotation, as the chickweed (which reseeds readily and
becomes a very present resident) can be a problem in low or slow growing
crops such as carrots and sometimes lettuce. But I think the concept of
selecting a weed that provides good ground cover to smother out more
damaging weeds has potential. Hope this helps.
Crop and Soil Science
Oregon State University
In an eight-year study soon to be published in Agriculture Ecosystems and
Environment we found weeds to be the most difficult and costly pest problem
to deal with in organically-managed row crops of Northern California,
specifically processing tomato and field corn. Disease and nematode
problems were almost absent, arthropod pests were occasional problems but
could be handled relatively efficiently and economically, but weeds were
costly to manage and escaped control in several years. High weed abundance
was the only pest variable associated with reduced crop yields in the
Weed management in the organic tomato system relied on the use of
transplants to give the crop a head start, mechanical cultivation, and hand
hoeing. This approach has been reasonably effective but resulted in pest
management costs that were 50% greater than those of the conventional
system, which used herbicides. Over the eight years the organic system had
average yields that were 10-15% lower than the conventional system and weed
competition appears to have accounted for part of this difference (nitrogen
availability also played a role). However, with the current high premium
prices for organic processing tomatoes, organic growers can spend the extra
money on hand hoeing and still be as profitable as conventional growers (or
even more profitable). Without premium prices, however, such increased costs
may not be justifiable in a system in which weed management expenses account
for over 20% of total operational costs.
The situation with corn was quite different than that of tomato because the
economic costs of organic pest management were less than conventional pest
management. And pest management costs in general comprised a small fraction
of total operational costs for both management systems. Cultivation
generally proved to be more cost-effective than herbicide use but the modest
use of herbicides did improve average yields (as in the low-input system)
because of occasional weed escapes. Average organic corn yields were about
5% less than conventional yields (again nitrogen played a big role here).
We are currently evaluating several additional organically-acceptable weed
management practices for tomato including flaming, weeder geese, and a
reduced tillage mulch system.
M. Sean Clark
Sustainable Agriculture Farming Systems Project
Department of Agronomy and Range Science
University of California
Davis, CA 95616
Hi, I recently joined Cascadian Farm after working 11 years as a weed
scientist with USDA/ARS. I was interested in your comments on weed
control. I think one needs to start with fields that are free of perennial
weeds and then prevent them from becoming established by always having some
type of ground cover or cultivation that doesn't allow easy establishment
of seedlings. Repeated cultivation can eliminate many perennial weeds but
one may have to forego a crop in order to kill the weed (not practical).
Once perennials become established I think we need more research on use of
fungi, mites, and insects that specifically attack certain species. I
would like to keep informed of your work and findings!
10401 N 1739 PRNW
Grandview, WA 98930
(509) 882-4401 phone
I have seen a finger weedingmachine in the Netherlands that works very
efficient, It can be used between the plants and can be fitted behind any
machine, Its an active rotating system activated by secundary
'fingers' that rotate into the soil. The weedingfingers are rubbery so
they don't damage the plants.
What is the place of suppressive crop cultivars in weed control?
Between plants that root deep there is a possibility but I don't have
positive results except for permanent situations.
Frits v/d Laan
Certified Organic Horticulture
The finger weeding machine and its use is described in the
most recent book published by the Sustainable Agriculture Network (SAN).
Steel in the Field: A Farmer's Guide to Weed Management Tools.
Have you considered using mulch for weed control. In
California we prefer yard trimmings mulch made from curbside
collected residential yard trimmings to keep the material from the
Clyde Elmore, weed specialist at UC Davis, recently
published results of weed suppression trials in "California
Agriculture", the bi-monthly Cooperative Extension journal. Applying
several inches of yard trimmings mulch was effective in controlling
weeds. The practice would be cost effective depending upon cost of
mulch and application. Clyde suggests thicker applications (the mulch lasts
two years or longer) would save application costsmaking this method
safe and economical.
PS.---We didn't sponsor this research project!
California Integrated Waste Managment Board
(916)255-2483; Fax (916)255-2573
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