Non-chemical Suppression of Perennial Weeds

Final Report for FNC96-137

Project Type: Farmer/Rancher
Funds awarded in 1996: $9,875.00
Projected End Date: 12/31/1998
Region: North Central
State: Iowa
Project Coordinator:
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Project Information


We have a diverse grain livestock transitional organic 335 acre farm in NE Iowa. We pasture farrow, hoop hog house finish around 1200 hogs per year. Our 70 stock cows consume the forages produced form a 5 year rotation. We have planted 3 miles of shelterbelts and pasture farrow along some of these shelters.

We have incorporated sustainable practices on our farm since 1983. Ridge tillage, management intensive grazing, and deep bedded swine production are a few sustainable practices we use.

The goal of the project was to document with replicated plots the effect of summer fallow combined with a cover crop on a troublesome perennial weed.

The fields targeted towards this research project were both in corn in 1995. Quack grass pressure was significant in both fields inspite if the chemical and cultivation used to control them. Both fields were planted to soybeans in 1996. No chemicals or fertilizer products were used. To aid in weed control, the soybeans were intended to be planted by June 1st. extreme wet weather delayed planting until June 16th. The extra delayed planting date reduced soybean yields to 39 BPA. Beans planted in mid May yielded near 50 bushels. The planting delay reduced yields but it did provide for good weed control with no chemicals. This was the first lesson from the research project. The combination of chemicals plus early planting would be more profitable unless the delayed planting no chemical beans were marketed differently.

Lets compare the cropping strategies this way:
- Gross income (yield x market price)
- Weed control costs

Early plant, Delayed plant, Delayed plant (if sold as organic)
Yield, 50 bu, 39 bu, 39 bu
Price/bu, $5.50, $5.50, $17.00
Gross $, $275.00, $214.50, $663.00
Weed control $, $25.00, $10.00, $10.00
Total, $250.00, $203.50, $653.00

Delayed plants would be a decrease of $46.50. Delayed plants sold as organic would be an increase of $403.00. Small wonder organic soybeans are hot!

We intended to have 2 locations for this trial. All of the details were in order until the land for the second set of plots was sold. I made several attempts to find another suitable location but to no avail. We then expanded the size of the first plot to cover all 10 acres and give us more replication.

No tillage work was done in the fall after the soybean harvest. Dr. Laura Jackson did some quack grass stand evaluation work.

The oat plots were drilled in on April 25, 1997, with conditions very good. The oats and seedings grew well. On June 24th, all of the plots were cut for an oat-hay crop. The entire field yielded 43 bales per acre. The quality was very good. We began tillage of the fallow plots as soon as the hay was baled. Fallow tillage continued until the third week of July. As we started to plant the cover crop plots, Dr. Jackson strongly suggested that we add a new treatment. This addition would be a full year fallow treatment. Dr. Jackson’s addition to the plot design allowed us to compare a traditional fallow operation to our other treatments.

The Japanese Millet and Sorghum Sudan grass cover crops got off to excellent starts. Beneficial rains and warm weather encouraged growth.

Dr. Jackson hired a group of students to assist with plot quack grass evaluation work. I was very impressed with the care and detail that went into their work.

Late in the fall of 1997, I let my stock cows graze on the research field. As winter set in, I fed the cows there, as well. I carefully moved to a fresh feeding site each day with the cows. The warm February 1998 weather thawed out the ground by the 14th of that month. I had to remove the cows from the field to stop damage to the soil. This was 4 weeks earlier than planned.

The cow manure was unevenly spread in the field. To improve nutrient uniformity, I hauled composted manure where it was needed.

I plowed the entire field on May 4, 1998. I observed significant soil texture differences as I plowed across the plots. The soil tilth was best on the plots with the oats red clover treatments. The soil in the full year fallow plots was the extreme opposite. The tilth in those plots was poor. Dry and unusually hot weather for May followed. I believe that this weather pattern lessoned quack grass pressure in the entire field. We were so dry by the third week of May that I had to postpone corn planting. A good rain fell on May 23rd. corn was planted on the 26th in perfect conditions. A timely rotary hoeing followed in early June. The weather then turned wet. Two cultivations were made but it was a struggle with the wet conditions. We took the soil samples for the late spring nitrate test in early July. The nitrate levels were very low.

The summer weather was nearly ideal. The corn grew out of the wet weather stress. The plots looked good but a noticeable height difference appeared. The tallest corn grew in the oat red clover plots.

We combine harvested the plots in early November. The corn stood well and tested only 20% H2O. I was surprised at the yield.

After harvest, we took stalk samples for the late season stalk test. Stalk nitrate levels were very low.

Dr. Laura Jackson, University of Northern Iowa, Biology Department was a wonderful partner in this project. She was determined from the first part of the project to create a learning environment for as many people as possible. She involved her students at the university in both field and classroom research activities. I was very impressed wither determined efforts to utilize the financial resources provided by SARE in a wise fashion. Under her direction, the number of experimental practices were expanded, more data was gathered than projected in the budget, and trips to observe the trial plots were combined with other activities. Dr. Jackson and I kept in close contact throughout the duration of the project. I would cooperate with her in another research project with very little hesitation.

Brian Lang, Iowa State University Extension Crop Specialist for NE Iowa, observed the trial on two occasions. I discussed some of the strategies with him on different occasions.

We successfully grew 3 crops in three totally different years using organically acceptable practices. This was an important goal of the project.

While none of the transitional organic crop yields were as good as the conventionally grown crops on the same far, all three crops were reasonably weed free. 1996 and 1998 had June weather conditions that were unfavorable to mechanically controlled weeds.

Growing good yielding organic corn was a real challenge in 1998. The wet weather leaked out most available nitrogen. I believe that the corn benefited greatly from the livestock incorporated in our farming system. Our stock cow herd filled three important requirements in this project.

1) They consumed the relatively low value forges that grew during the fallow cover crop year.
2) They fertilized the soil as they spent much of the 1997, 1998 winter on the field.
3) Their composted yard manure was spread on the “manure skipped” areas of the field in the spring.

I learned some important lessons on non chemical control of quack grass. I battled quack grass with chemicals and tillage for 25 years. My fear was that removing the chemical from the control strategies would produce quack out of control! This was a great fear. I learned that quack grass comes and goes, chemicals or organic. In 1996, the cool and very dry summer sent the quack into dormancy. The soybeans, planted in mid June, dwarfed the quack. Quack did well in most of the plots during the oat fallow season. Dr. Jackson did excellent stand evaluation work that year.

While I worried about weed control in general in the corn in 1998, I kept a real close eye on the quack grass. Again, the weather provided a larger influence on the quack grass rigor than our tillage cover crop attempts. I plowed the field in early May. This and the hot dry May weather suppressed this perennial. When the quack recovered with the cool wet June climate, the corn was a vigorous competitor.

In another year, reversing the May-June condition could produce entirely different quack pressure.

The bottom line to me is this: quack grass comes and goes, if it gets really serious, than consider extensive fallow work with possibly a cover crop but by all means, watch the weather. Plan field activities aimed at quack control for times when quack is under stress.

If I could do the grant over again, I would change the perennial weed that we tried to suppress from quack grass to Canada thistle. This is a weed that does well every year! Stand counts are easy. Thistles are a worse problem. They thrive inspite of all the chemical and tillage practices used on then. I really wished that our trials were aimed at thistle control.

I really enjoyed this research project. Weeds did not “run me out of business”. The fear of poor weed control with no chemical use lessened. I developed more of an aggressive attitude about learning how to live with “plants out of place”. When Dr. Jackson and I wrote for the grant, changing the farm to certified organic was an option not heavily considered. Our farm now is transitioning to certified organic. We produced organic corn and soybeans in 1998. Next year we will add organic oats and certified pork.

Learning how to grow crops without chemicals is critically important for me today. This project helped.

I would strongly recommend another producer to follow the example of this project. Both parties benefited. One of the inherent difficulties in non chemical agriculture is information on strategies for pest control. Chemical representatives are out of the information loop. Replicated field trials like these are a source of information on chemical free cultural practices. Dr. Jackson did a literature search that provided valuable information on this subject, as well.

It is difficult to estimate the impact of farmers adapting cultural practices. To realize the true benefits of chemical free farming, market options should be considered. The current premiums for organic soybeans underline this.

Chemical free farming offers significant social and environmental benefits, too. Water pollution and farm worker pesticide exposure are lessened or even eliminated.

Criticism of soil erosion in organic row crop production is fairly common. Exposed soil is less likely to erode if there is good soil aggregate structure. Aggregate structure is best formed in a healthy grass sod crop. A year of oats/red clover develops some good soil structure. I saw this in the plots. There was far more erosion (and poor soil structure) in the full season fallow plots.

We hosted two field days to expose the public to our SARE project. Both field days were well attended. In July 1997 approximately 50 people attended, and in July 1998 45 attended. A special note goes to Dr. Kathleen Delate, Iowa State University Organic Specialist, who attended the 1998 tour and offered comments on the plots.

I attended one of Dr. Jackson’s Environmental Science classes in 1997 to discuss the results of the quack grass suppression plot work.

Presentations on the entire research project will be made at these upcoming conferences:
- 1999 Practical Farmers of Iowa annual meeting
- 1999 Upper Midwest Organic Farming Conference (we will have a full non profit booth display at this 1000+ conference)
- 1999 NE Iowa Organic Farming Conference
- 1999 CHARM Holistic Management Farm meeting

Results will also be shared in Dr. Jackson’s classroom and her writings.


Participation Summary
Any opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the view of the U.S. Department of Agriculture or SARE.