Joel Gruver

WIU Agriculture

Improving Weed Management

in organic grains

This is a good time of year for pondering ☺

https://www.organicvalley.coop/blog/farming-in-winter/

Weed, pest

& disease

pressure

What is

YOUR

context?

Geographic

spread

of fields

Soil

types

Fertility

Drainage

Infrastructure

(buildings, bins fencing, conservation structures…)

Historical weather

Equipment

?

Field

shapes

& sizes

Soil

types

Community

Human resources

Field

shapes

& sizes

Employees

Landlords

Vendors

Consultants

Equipment

Infrastructure

(buildings, bins fencing, conservation structures…)

Geographic

spread

of fields

Historical weather

Weed, pest

& disease

pressure

Drainage

Fertility

Family

YOUR goal is to IMPLEMENT:

1) weed suppressive

CROPPING SYSTEMS

+

2) weed control practices

that fit YOUR context

Some systems & practices that work well for other farmers are a poor fit for YOUR soils, topography, weed types, scales of enterprises, human resources, MARKETS…

The aim of weed management strategies

in organic farming is to

maintain weed populations at a manageable level through a range of husbandry approaches THROUGHOUT the rotation,

so that direct control actions

within individual crops

have a greater surety of success.

https://orgprints.org/id/eprint/8162/1/5.pdf

UNDERSTANDING ORGANIC WEED MANAGEMENT

Effective physical weed control (PWC) requires a systems approach to weed problems.

In practice, this means that PWC relies on prior application of agronomic practices aimed to:

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1. reduce weed emergence through the use of preventive methods (crop sequence choice, primary tillage, false seedbed technique, blind cultivation, use of cover and⁄or smother crops)

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• reduce weed competition through cultural methods that improve crop competitive ability (use of appropriate crop genotypes, transplants, sowing⁄planting pattern, fertilization strategy).

Paraphrased from Bàrberi and Paolini (2000)

UNDERSTANDING ORGANIC WEED MANAGEMENT

Visiting successful organic farms

WHEN they are performing key operations

is even more valuable

Field days and conferences are great opportunities

to listen to experts and network BUT…

When farmers contact me with Qs about organic farming,

I normally start by identifying EVERY organic farm

in their county and adjacent counties

You want to learn

what is

and is NOT

working in your area

Information from LOCAL organic farms is very valuable…

Supportive relationships with LOCAL farmers are invaluable!!

organic & conventional

We all need MENTORING on our organic journey

Effectiveness of PRACTICES ^{& products}

on organic farms

is strongly influenced

by farmer

SKILL and WILL

prioritization, timeliness,

INTEGRATION of practices

and commitment!

This compilation of farmer profiles illustrates 9 different contexts for

Some farmers are always looking for the MISSING PUZZLE piece on their farm

New technology??

An alternative approach is to focus on how puzzle pieces fit together

Less dependence on

direct control

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More effective

direct control

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Key factors leading to improved weed management at the WIU Organic research farm

- Improved management of cover crops and crop residues resulting in better soil tilth

(Alternative cropping systems (NT, SC, HB fallow…)

- Establishment of better crop stands using neighbor’s

12-row air planter w/ RTK guidance

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- Better seed bed preparation (including FSBing)

- More intensive blind cultivation (tine weeder and rotary hoe)

- Precision row cultivation equipment for 1^st cultivation

- Earlier row cultivation when conditions permit/warrant

- More complete hand rogueing of weeds

- Periodic inclusion of bare fallow (mostly < 1 summer month)

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Focus is on equipment for direct control of weeds

http://www.sare.org/Learning-Center/Books/Steel-in-the-Field

F

FREE download

Lots of diagrams of tools

& farmer profiles!

Published 2 decades ago!

Great discussion of a wide variety of tools

Great discussion of tool components

We dedicate this book to our dear friend, colleague, and coauthor, Charles “Chuck” Mohler. Unfortunately, Chuck passed away in April 2021 and was not able to witness his 15-year-long book project to its deserved culmination. Chuck was a unique individual in that he was not only a brilliant scientist able to produce some of the most innovative weed science research, but he could translate this often highly technical research into practical and useful information and advice for growers

In Memoriam –

Charles L. Mohler

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Dr. Mohler obtained a PhD in Ecology and Evolutionary Biology from

Cornell University in 1979.

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His dissertation research involved

plant community ecology –

specifically, the predictability of species

at field sites, as driven by interactions

w/ other species and

environmental conditions

which he tested through

careful field work in

natural plant communities

Are you familiar with this book?

Weed:nutrient relationships discussed in When Weeds Talk:

A smorgasbord of anecdotal information,

ripe for testing by the next generation of Chuck Mohlers

and innovative farmers

Weed:nutrient relationships discussed in When Weeds Talk:

Have you TRANSLATED

this type of info into practical weed management strategies?

2021

Research shows that some weeds are highly responsive to the availability of

some nutrients

Over application

of manure

• Many weed species are highly responsive to soil fertility.
• Weeds often have 1.5 to 3 X higher N, P, K, & Ca concentrations than the crops they are growing with.
• Excess fertility increases weed growth rates and may enhance weed germination.

Adapted from Moehler

INCREASE CROP competitive advantage

REDUCE weed pressure

CROPPING SYSTEM STRATEGIES

for weed management have 2 main priorities:

Opportunities to INCREASE crop competitive advantage !!!

Plant later

- soil must be warm enough for

rapid crop emergence

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Prepare a good seed bed

- weed-free and favorable for

uniform crop emergence

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Optimize planter performance

- DEPTH, down pressure,

closure of slot…

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Accelerate crop canopy closure

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- Plant well adapted tall leafy crops/genetics

- Increase crop populations

and/or adjust row spacing*

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- Apply seed treatments

and/or banded fertilizer

Opportunities to REDUCE weed pressure

Promote weed seed predation, decay & DORMANCY

- Crop rotation, cover crops, targeted tillage and LATE planting

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Minimize production of weed propagules (seeds, rhizomes…)

- Crop rotation, weed zapping, walking of crops, termination of

excessively weedy crops (e.g., harvest as forage, graze, use as CC…)

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Optimize performance of direct control equipment

- right equipment + right timing, setting, ground speed & soil conditions

Right timing = effective targeting of weak links in weed life-cycles

Use blind cultivation and 1^st cultivation effectively!!!

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Innate?

Environmentally

induced or

enforced?

Become a student of weed seed dormancy!

FREE download

A good place to start your investigation

This interesting article discusses

a wide variety of factors that effect

weed seed dormancy & germination

(e.g., nutrient levels, light, temperature, O₂ & CO₂ ,

crop residues, depth of burial, tillage implement…)

and opportunities to exploit these effects

��Published online by Cambridge University Press:  06 June 2018�Lisza Duermeyer et al.��Abstract��Nitrate promotes seed germination at low concentrations in many plant species, and functions as both a nutrient and a signal. As a nutrient, it is assimilated via nitrite to ammonium, which is then incorporated into amino acids. Nitrate reductase (NR) catalyses the reduction of nitrate to nitrite, the committed step in the assimilation. Seed sensitivity to nitrate is affected by other environmental factors, such as light and after-ripening, and by genotypes. Mode of nitrate action in seed germination has been well documented in Arabidopsis thaliana and the hedge mustard Sisymbrium officinale. In these species nitrate promotes seed germination independent of its assimilation by NR, suggesting that it acts as a signal to stimulate germination. In Arabidopsis, maternally applied nitrate affects the degree of primary dormancy in both wild-type and mutants defective in NR. This indicates that nitrate acts not only during germination, but also during seed development to negatively regulate primary dormancy.

Regulation of seed dormancy and germination by NITRATE

This research indicates that higher Ca availability does NOT suppress

Large Crabgrass

More research is needed on how CALCIUM

impacts the germination and growth of other weeds

De Cauwer et al. (2011) found that total weed seed bank density was lowest in plots amended with compost and highest in plots amended with liquid cattle manure. Reductions in weed seed densities in soil, especially of hard-coated species such as Chenopodium spp., were correlated with increases in total microbial biomass and soil organic carbon content

Biological effects on weed seeds??

Tillage

triggers the germination of weed seeds

in many ways

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Some tillage practices trigger more weed germination than others!

(by increasing exposure to stimuli such as light, oxygen, temperature fluctuations…)

https://orgprints.org/id/eprint/31022/25/PA_007_False-seedbed_final_QR.pdf

Stale seedbed (SSB) technique

(modified from a rice production guide)

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SSB is a seedbed prepared weeks or even months prior to sowing or planting a crop with a goal of flushing out germinable weed seeds prior to the planting of the crop, thus depleting the seed bank in the surface layer of soil and reducing subsequent weed seedling emergence.

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The three ‘golden rules’ of SSB:

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1) 85-95% of the seed in a seed bank have innate dormancy at any given time and most of the other 5-15% will germinate quickly with the right environmental conditions.

2) Tillage is the most effective means of getting weed seeds to germinate.

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3) Most weeds emerge from top 2” of soil.

Will these weeds be fully terminated

by the last tillage pass before planting?

Fernholz

Is your last pass capable of fully terminating ALL weeds?

Corn emerging rapidly and uniformly

~ 5 days after planting

WHY DOES THE SOIL SURFACE LOOK CRUMBLED?

The field was recently rotary hoed!

Blind Cultivation for Early-Season Weed Control in Organic Grains

While the immediate impact of blind cultivation is not visually dramatic,

the ROI is often high because blind cultivation is fast, cheap and

targets the most vulnerable stage in the life cycle of many annual weeds

Blind cultivation terminates white thread seedlings

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& creates a loose, dry

soil surface environment

(sometimes called a dust mulch)

unfavorable for weed germination

until the next rain

Blind cultivation tools

provide the most “action”

when they are shattering a crust

Blind cultivation tools move more soil

(& terminate more weeds) when the initial soil condition is rough and residue rich.

This is an extreme case but planting in furrows

or leaving a ridge of soil over crop rows

improves the effectiveness of blind cultivation tools

We use an M&W

high residue rotary hoe and an Einbock

tine weeder @ the WIU Organic Research Farm.

What blind

cultivation

tools are you currently using?

Tine weeding has worked very well for soybeans (pre- and post emergence).

We have limited experience with corn.

Row cultivation tools

Modified IH 153

When properly set, inter-row weeds are dessicated and in-row weeds are buried

Extended spacing between

sweeps improved residue flow

New Additions

Improved lateral stability and residue sizing

It is possible to achieve a high level of in-row weed control using a row crop cultivator (even when in-row weed pressure is high)…

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…but this can only be accomplished during the

1st cultivation

WIU = testing ground for prototype Accuraflow cultivator

Much easier adjustment allows more accurate control of soil flow into the crop row

Mechanical, GPS and sensor-based guidance systems can significantly IMPROVE blind and row-cultivation

Do you have experience with guidance systems?

Guidance -> reduced operator fatigue and easier monitoring of cultivator

Old school guidance

is making a come-back

from Steel in the Field

6/22

7/7

7/16

2 keys to successful

cultivation

FINISH

STRONG

START

RIGHT

= rapid crop growth after cultivation

STARTING RIGHT

Prepare a weed-free seed bed suitable

for your planter to establish a good stand

Plant the straightest rows possible

Set planter carefully and check seed depth

and spacing multiple times

Take blind cultivation VERY seriously!!!

Take 1^st row cultivation VERY seriously!!!

Manage soil for good tilth

WITHOUT good soil tilth, crumbling of soil from weed roots and flow into the row will be inadequate!

Timeliness strongly impacts the effectiveness of cultivation

Has your area

experienced

increasing frequency of

extreme weather events?

As a primarily receipt driven program,

we have been forced to make adjustments

More nimble utilization of windows of opportunity

New technologies

Alternative cropping systems

Crop/cover crop diversification

We now start cultivating when the crop

is still very small

IF there is weed pressure and soil conditions are fit

Planting LATE makes much it easier

to achieve good weed control

We have planted sunflowers the 4^th week

of July and harvested

>1500 lbs of mature seeds

Some organic weed control tools

are less sensitive to soil moisture

Weeds must be taller than crop

Great compilation of practical recommendations for organic no-till soybean production

“Too much about the roller crimper and not enough about no-till organic farming.

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A crimper is not the all-to answer for organic no-till farming...not by any means.

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In the right environmental condition, it is a useful tool to terminate some cover crops, but the book makes it seem as though it solves the termination issue mechanically.”

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Amazon review

by organic farmer in IA

Year 1: Corn

Year 2: Field pea → rye

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Year 3: rye → NT soybean

T

T

T

We now normally follow small grains or peas:

T

T = tillage

volunteer peas

NT organic soybeans following corn is HIGH RISK

It is often difficult to establish

an adequate stand of cereal rye after corn harvest

Early planted rye w/ adequate N is very likely to produce a strong stand

We have been investigating

Solar Corridor Cropping Systems

(SCCS)

at the WIU Organic Research Farm for

5 years and have evaluated row configurations,

N management,

corn hybrids, cover crops and impact on subsequent

crops.

We have had good weed control in SCCS but weeds will thrive in SCCS if you give them an opportunity.

Many sustainable growers subscribe to the philosophy of “feed the soil, not the plant.”

Our whole farm approach to weed management

follows the same line of thinking — only we call it

“weed the soil, not the crop.”

Instead of relying on the cultivator or the hoe

to save the crop from the weeds,

we use cultural practices, including cover cropping, bare fallow periods, rotation and shallow tillage to reduce the overall weed pressure in the soil.

Description of fallow season

Typically, we grow one cover crop in the spring

and one in the fall. Between the first cover crop and the second is a window of opportunity to use tillage to reduce the number of weeds in the soil. The length of this bare fallow period, and the type and intensity of tillage required, depends on the life cycle and growth characteristics of the most pressing weeds.

https://covercropsincorporated.wordpress.com/author/aubreyfornwalt/

There are several collections of our articles on the web

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Decades of experimentation and experience by farmers, technicians and scientists are presented clearly and practically, making this work an essential contribution not just for world food security but for the food sovereignty of the 2 billion smallholders who produce the bulk of the world’s food.

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Dr. Eric Holt-Gimenez

http://tinyurl.com/3cpdp3e2

Fallow periods with intensive cover cropping are a proven practice!

In 2017, we decided to “pull the plug”

on a very weedy no-till soybean field

at the WIU Organic Research Farm

The following season, this field set a new record

for corn yield at the

WIU Org Research Farm – 225 bu/a

The soil was exceptionally mellow,

weed pressure was low,

& management was easy!

High Yield Corn after High Biomass Fallow Study

Dr. Joel Gruver and Andrew Clayton

Introduction:

During an unusually hot week in May 2017, soybeans were drilled into rapidly transpiring cereal rye and seed placement into moisture was inconsistent. The resulting stand of soybeans was poor and provided little competition for emerging weeds. In late August, with weed seeds rapidly approaching viability, we made the tough decision to till under most of the field. The following season, we planted 2 corn hybrids with high yield potential at an earlier planting date and higher population than normal. Record yields resulted and projected income for related scenarios opened our eyes to the potential for high biomass fallow followed by high yield corn to be a profitable cropping system on organic farms.

The high corn yields achieved in 2018 resulted from the convergence of multiple factors:

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a) Corn hybrids with genetic potential for high yield (PH6878, GH59R5)

b) Higher than standard population (35.5k)

c) Earlier than standard planting date (1-2 weeks early)

d) Excellent soil tilth

e) High nutrient availability despite a moderate application rate of poultry litter

f) Favorable weather conditions

g) Excellent weed control

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The high biomass fallow (aka regenerative year!) in 2017 directly contributed to 3 key factors in 2018: excellent soil tilth, weed control and nutrient availability and most likely resulted in better net income over 2 years than if we had taken the soybeans to harvest in 2017.

We used an enterprise budget tool to evaluate scenarios and found that a regenerative year followed by high corn yields

had more profit potential than expected

Stay-tuned for results of our high-biomass fallow experiments

Livestock on the Land is a story by Practical Farmers of Iowa about the ways that farmers are building a regenerative agriculture by centering their operations around the animals they care for. Whether it's through rotational grazing or cover crops or fertility for crop fields, livestock hold the key to protecting our soil, cleaning up our water and even providing habitat for wildlife. But most importantly, livestock give farmers a chance to get started, grow businesses, provide for their families, work together, and ultimately, bring back the next generation to start it all over again.