Evaluating and Demonstrating Weed Control Options for Direct Seeded Fall Vegetable Crops

Final report for ONC18-038

Project Type: Partnership
Funds awarded in 2018: $29,495.00
Projected End Date: 12/01/2019
Grant Recipient: K-State Research and Extension-Douglas County
Region: North Central
State: Kansas
Project Coordinator:
Tom Buller
Kansas Rural Center
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Project Information


This project researched, analyzed and demonstrated the efficacy of several minimal tillage techniques to manage weeds generally, but especially amaranthus weeds, commonly referred to as pigweed, in fall grown vegetable crops that are usually direct seeded including spinach, beets, and carrots.

Through trials on three certified organic vegetable farms, the project collected information about the efficacy of various non-chemical and minimal tillage methods to manage weeds, while analyzing the efficiency of labor usage, in order to inform growers about optimizing their integrated weed management strategy.  During two years of field trials numerous challenges plagued the participating farmers limiting the available data, but the overall conclusion was that no one stale seedbed technique was ideal, and that multiple passes or multiple techniques needed to be used together to create optimal weed control.  None of these techniques proved to burden farm labor excessively.   Two of the participating farmers plan to continue using the tools for stale seed bedding, most likely in concert, with either occultation followed by a pass with the power harrow or the flame weeder. The third farmer is scaling back vegetable production in future seasons.  

This information was shared with other growers in the area through field days in 2019 and 2020 and example plots available for the 2019 Kaw Valley Farm Tour.  Additionally, the information was shared at presentations about vegetable production in Northeast Kansas and Northwest Missouri.  

Project Objectives:

This project:

  • Trialed several non-chemical, minimal tillage weed control practices to manage weeds in fall vegetable crops including spinach, beets, and carrots on three farms in Kansas
  • Monitor various performance metrics of the different techniques such as labor time necessary for adequate weed control and harvest yield to provide a detailed picture of management technique performance.  No significant differences in weed management was achieved using any of the techniques separately. 
  • Compile and disseminate information to aid farmers in decision-making for weed management strategies



Click linked name(s) to expand/collapse or show everyone's info
  • Kevin Prather (Researcher)
  • Jill Elmers (Researcher)
  • Jen Humphrey (Researcher)


Materials and methods:

This project used on farm trials on three farms.  Each farm utilized various stale seedbed approaches to try and control weeds in fall direct seeded crops.  The reports of their efforts are below. 

Farm 1- Year 1

Multiple bed trials of spinach and beets utilizing occultation, power harrow and flame weeding to create a stale seedbed.

First attempt
*July 17 - prepped 2 beds and covered with tarp .
*August 9 - tilled and shaped 4 experimental beds and 2 control beds .
*Aug 17 uncovered 2 tarped beds .*Aug 18 fertilized all 8 beds .
*Aug 19 power harrow 2 beds and pressed 6 with power harrow roller to lightly incorporate
fertilizer .
*Aug 19 seed 4 beds spinach and 4 beds beets .
*Sept 10 tilled in all beds due to low germination and high weed pressure

Second attemptCould not include occultation as timing was not right to cover a new area for multiple weeks. 
*Sept 12 fertilized 3 beds .. power harrowed all 3 beds to incorporate fertilizer

*Sept 19 tilled control bed, power harrowed middle bed, flame
weeded south bed... seeded spinach, 1 control bed, 1 power harrow bed, 1 flame
weed bed .. was unable to implement tarp this round due to insufficient time... set
up mini-wobblers for irrigation
*Oct 1 cultivate with stirrup hoe - control, power harrow, flame ... number of weeds and soil moisture made up the difference
between control and other beds... very little pigweed by this point, mostly henbit
**Oct 22 cultivate with stirrup hoe - control, power harrow, flame... Worker fatigue likely made up the difference in times
**Dec 5 two workers harvested all 3 beds... 

Farm 1- 2019 Report

*July 24 - prepped 2 beds and covered with tarp .. (30 minutes)
*August 18 - tilled and prepped 4 experimental beds and 2 control beds .. (40 minutes)
*Sept 4 uncovered 2 tarped beds .. (10 minutes)
*Sept 4 fertilized all 8 beds .. (30 minutes)
*Sept 4 power harrow 2 beds and pressed 6 with power harrow roller .. (20 minutes)
*Sept 4 seeded 3 beds spinach (20 minutes) and 1 bed paperpot spinach (12 minutes) and seeded 3 beds beets (20 minutes) and 1 bed paperpot beets (12 minutes)
*Sept 21 tilled in all beds except paperpot beets and spinach, due to low germination from soil crusting and seed washout from heavy rainfall (10 minutes)
*Sept 28 re-tilled 1 row (5 minutes), re-power harrowed 1 row (5 minutes), flame weeded 1 row (8 minutes) for spinach re-planting
*Sept 28 reseeded 3 beds of spinach (20 minutes)
*Oct 15 cultivate with stirrup hoe - control (10 minutes), power harrow (10 minutes), flame (10 minutes), paperpot (12 minutes)... due to late planting, weed pressure was low and cultivation time was fast and consistent between the trials

We managed to harvest 15 bunches of beets (Oct 20) from the paperpot row of beets. The majority of the planting was destroyed by deer over the course of a few days. Before the deer pressure, the health and vigor of the planting was better than we have ever had in fall beets. We will definitely consider paperpotting fall beets in the future.

Our late planting of spinach didn't get to a harvestable size before the cold of winter came. It is currently under row cover and we plan to begin over-wintered harvest as soon as weather permits.


Farm 2 2018 Report

We were able to plant carrots and spinach in two different setups plus the control. Control consisted on our usual mow cover crop, let foliage die, leave bed alone then till and plant fall crop. We planted spinach on 8/28 and carrots on 8/27.
For the tarp setup, we applied the tarp on 7/20. Removed on 8/27. Ground was very compacted due to water pooling on tarp and weighing down the soil. We used the back roller of the power harrow to try and rough up the top surface enough to use the seeder. Seeding was tough as the roughing up didn’t help much. Spinach and carrots planted as schedule above.
For the power harrow setup, we mowed cover crop and tilled then let ground sit. Once ready to plant we went over with the power harrow. Great tool. Planting same schedule as above.
We used constant irrigation to aid in germination of all beds. We got a late heat wave and the spinach did not germinate in any bed enough to keep. We tilled in 9/13.

Farm 2-2019 Report

Fall 2019 – cool and wet August; hot and dry September

We utilized the paper pot transplanter to plant both carrots and spinach this year.  We had spotty germination with the spinach in the paperpot trays, but the carrots did well.  The carrots should only be in the paperpot trays for a few weeks before planting as they start to get a tap root very quickly.  With both row we used wobbler overhear watering and we over watered causing a lot of the spinach to rot.  We picked about 15lbs from our 100ft row before the deer discovered it and proceeded to pull it all up.  About a month later we lost all the carrots that were at least 3” high to the deer as well. Never had deer eat carrot tops, so I guess they must have been really hungry.

We used the silage tarp to cover a row for spinach and carrots.  Tarp was on for 4 weeks.  The tarp did a great job of killing off any weeds underneath. We did till before covering.  After pulling up tarp, ground surface was packed down so used the power harrow to make a lovely bed for seeding.  This combination worked great and we have one very nice bed of spinach that we picked from until January 1.  The carrots are still in the ground and row covered, so we will see what it looks like in March.  The hot September was challenging to get germination and growth before getting cold. 

We used the power harrow on a row each of carrots and spinach.  Neither germinated before the weeds took over.



Farm 3-2018 Report

The trial bed is about 70 feet long by about three feet, with two dense plantings of carrots in that bed. It is currently covered with row cover but we've had trouble keeping the cover down as winter progresses.
With such a dry season, we didn't try to work the bed the end of July. We tilled, watered several times to try to get the pig weed to sprout because the soil was so dry. On August 2, we determined we had enough sprouts to try to cover it. We covered the bed with the cover white
side up and weighted it down.
On Sept. 4, we removed the cover because even though 6 weeks covered would have been ideal, we were running out of time for fall production. We planted in one bed, 70 feet long by three feet wide, with two plantings at either edge.
On Oct. 1, there are two photos that show pig weed in the row along with other weeds. Believe it or not, this was substantially less than what we would have otherwise had. The carrots sprouted and grew to about four inches. We weeded down the middle and the edges for about three hours by hand.
On Nov. 8, with cold weather approaching, we spent three hours weeding again, then mulching them throughly with straw and putting row cover over them. The carrots were only about two to three inches long so we wanted to see if we could get through winter with them and thin again in the spring to encourage larger growth.
Wildlife, a few errant chickens and wind have played havoc on the cover, but final data will be reported in spring 2019 at harvest. 

Farm 3- 2019 Report

Due to heavy rainfall and saturated fields fall crops were not successfully established.  

Research results and discussion:


On flame weeding as a control
Flame weeder worked well for small pigweed, typically our worst fall weed.  With appropriate timing the flame weeder provided good control, but timing was challenging in dry weather for fear of sparking fires.  

Center: Bed that has been flame treated, 2 weeks after treatment.  See adjacent rows for relative pigweed pressure on rows that were not treated.

In areas where volunteer wheat spouted, the flame weeder did not affect the wheat that sprouted as a weed. 

On the power harrow

The power harrow makes very nice seed beds, better than a rototiller... but it appeared to sprout more weeds than the tiller as the more viable seed bank doesn't get buried. Power harrow does not work on cover crop incorporation or bigger weeds, so it must be used early in the growth of weeds.  It also worked well to prepare soil after it had been compacted in the occultation process (see below).


On Occultation

Tarp used for occulation
Occultation tarp spread over field

Occultation provided challenges with management and timing.   The tarp can be a challenge to manage and sometimes catches and holds water on top which causes some soil compaction.  After the tarp had created compaction, the power harrow was a great tool to loosen the seedbed and prepare it for planting. 

Picture of compaction created by occulation tarp
Compaction created by tarp for occultation

General Comments

In year one we had a great deal of trouble due to weather.  An extreme drought persisted in our region until early October and hot dry weather inhibited the establishment of fall crops in early to mid-August which is the normal window.  Several trials failed due to poor crop germination and had to be repeated a few weeks later as soil temperatures dropped.  Overall using these methods alone seemed to show poor results with high weed pressure in test beds, however some experimentation by Farms One and Two suggested that using the various methods together would more effective than using them by themselves.
Overall, timing was the biggest challenge for using these weed suppression methods. If timed correctly flame weeding appeared to be very effective.. In a perfect world a better process might be using these methods together would be a 2+ month process: 1) start with a relatively clean field with minimal plant material; 2) fertilize and prepare beds with power harrow; 3) if no rain comes, overhead irrigate, then cover with tarp and leave for 6 weeks to kill most viable surface weed seed; 4) pull back tarp, overhead irrigate again to sprout any remaining weed seeds and wait for a week or so; 5) flame weed any weed seeds that sprouted from irrigation; and 6) seed crop into flame weeded beds.

In year 2 we had a different set of problems that hindered a true experiment.  We had excessive precipitation through most of the year, tapering off in August when the trials began. The farm that had heavier clay soils was not able to recover from the precipitation and did not establish any fall crops.  The other farms were able to establish crops, but the harvest of those prior to the end of the experiment was limited.  Most crops that were able to be harvested were destroyed by deer at both locations.   Using more observation rather than more substantive data, Based upon two years of experience the farmers concluded that using the stale seedbed techniques individually did not seem to have a significant effect, and that using any of the techniques in combination was better than any technique used alone. None of the techniques seemed to need too much extra labor, but the cost of the implements along with minimal impact certainly would make it hard to justify using these without a more concerted integrated weed management approach.  

Although we only had 2 farmers trial the paper pot transplanter and only in one of the two seasons due to organic certification concerns in 2018, both farmers reported being happy with that tool for reasons other than weed management. In spring experimentation with the paper pot transplanter, so that they would be prepared for the fall trials, the farmers noted a number of good qualities.  First the spring was very wet, so being able to put in transplants allowed crops to be established where direct seeded beds had washed out.  The jump start on field growth provided but the paper pot transplanter also helped the spring crops outcompete the weeds, as we had expected.  Unfortunately, both farmers using the system in the fall did have problems with paper pot transplanted crops being almost totally destroyed by deer pressure in the fall, so no real measurable yields were available to support the observed effects from the spring season.  



Participation Summary
3 Farmers participating in research

Educational & Outreach Activities

2 Consultations
1 On-farm demonstrations
1 Tours
5 Webinars / talks / presentations
1 Workshop field days

Participation Summary:

98 Farmers participated
3 Ag professionals participated
Education/outreach description:

For outreach in the 2018 we had four main efforts.  One on farm demonstration and discussion held in September at Mellowfields Farm.  Six farmers attended, and we demonstrated the weed management equipment and discussed the course of the project this year.  Attendees were able to observe the trial plots. Red Tractor Farm was a stop on the Kaw Valley Farm Tour in October, so we made signs for the trial beds that described the project and the trial technique- occultation.  In the fall and winter Tom Buller was able to make two presentations using information gathered in the first year.  One was a presentation on Conservation Agriculture at the Great Plains Growers Conference on January 11, 2019 that incorporating observations from this project.  Another presentation occurred at the Nebraska Sustainable Agriculture Society's Annual Meeting on February 8, 2019.  This presentation covered the whole course of the project to date, from initial conception to the end of the first year.  

In 2019, this project hosted a field day in conjunction with the Kansas City Growing Growers program at Moon on the Meadow farm focused on weed control.  Information developed from this project was incorporated into three additional presentations on weed control,  one in conjunction with Growing Growers and two to local farm audiences. The information gleaned will be incorporated into programming in 2020 on weed management for the Lawrence Common Incubator farm and the Wichita, KS Growing Growers program.  

Learning Outcomes

37 Farmers reported changes in knowledge, attitudes, skills and/or awareness as a result of their participation
Key changes:
  • - Knowledge of organic weed control options

Project Outcomes

3 Farmers changed or adopted a practice
1 Grant received that built upon this project
2 New working collaborations
Project outcomes:

While this project faced a number of challenges due to two years of extreme weather (drought in 2018 and extremely wet weather in 2019) as well as intense deer pressure on two farms in 2019 it did allow us some positive outcomes:

  • It provided demonstration plots of stale seed bed techniques which are not commonly practiced in the area.  This helped the participating farmers explore this technique but it also gave other farmers in the area an opportunity to explore to the practice. 
  • It provided hands on access to several new tools for the area, a power harrow, a paper pot transplanter and a flame weeder.  These tools did not individually solve weed management problems, on farm experimentation utilizing them together for a series of passes on stale seedbedding proved promising. 
  • It created interactions between local farmers and K-State Research and Extension to help with weed management in vegetable production systems.  The outreach part of this program has created some ongoing engagement to help other farmers with weed management challenges.  
  • It provided information for ongoing education about organic weed control in northeast Kansas, that will be used in future educational outreach.  Particularly a specialty crop block grant was received by K-State Research and Extension Douglas County to, in part, provide education on weed control and other topics to beginning farmers.  The information gleaned in this project will inform that effort directly.  

Information Products

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.