Blind Cultivation for Early-Season Weed Control in Organic Grains - Transition to Organic Partnership Program

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Fact Sheet Series 22-2

Blind Cultivation for Early-Season Weed Control in Organic Grains

SUMMARY
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Blind cultivation provides early-season control of both in-row and inter-row weeds, giving crops a
competitive advantage and improving effectiveness of row cultivation later in the season.
It is commonly used in organic corn and organic soybean production systems.
It targets weeds germinating above the crop planting depth; germination depths for common weeds are in
Table 1.
Timing is critical because it is most effective against very young weeds.
Tine weeders and rotary hoes are commonly used for blind cultivation, details on these tools are included
below.
Crop-specific recommendations are included in Tables 2-5.

INTRODUCTION
Successful weed management on organic farms
integrates DIRECT control tactics that terminate
weeds (e.g., tillage, flaming and weed zapping) with
INDIRECT tactics that reduce weed pressure (e.g.,
higher crop populations, extended crop rotations and
other practices that promote weed seed dormancy
and mortality). This factsheet focuses on a multifunctional tactic called blind cultivation that efficiently
terminates very young weeds AND reduces weed
pressure by creating a soil surface zone unfavorable
for germination. While the immediate impact of blind
cultivation is not visually dramatic, the return on
investment is often high, because blind cultivation is
fast, cheap and targets the most vulnerable stage in the
life cycle of many annual weeds.

UNDERSTANDING THE VALUE OF BLIND
CULTIVATION
Early season weed control should be a high priority
on organic farms because it gives crops competitive
advantage and improves the effectiveness of row
cultivation later in the season (1–3). Blind cultivation
is an early season practice that targets weeds
germinating above the crop seeding depth, so it is most
appropriate in crops planted ≥ 2” and most effective
in controlling weed species that germinate near the
soil surface. It is commonly used in organic corn and
soybean production systems but can be used in small
grains including oats, barley and wheat (4) and in some
vegetables.

Timing of blind cultivation is critical because it most
effectively controls weeds between germination
and emergence (the white thread stage) but recently
emerged weeds can be controlled by aggressive blind
cultivation. The most popular tools for blind cultivation
are tine weeders and rotary hoes but other types of
harrows are also used. Timing, tools and management
for specific crops are discussed in subsequent sections.

MANY FACTORS IMPACT EFFECTIVENESS OF
BLIND CULTIVATION
Planting depth: This is the first consideration for
effective blind cultivation. There must be sufficient
space for soil disturbance above the crop seed. This is
one of the reasons why many organic farmers plant
deeper than is typical on conventional farms with the
same soils and crops. Other reasons may include soil
drying after seed bed preparation, cloddy seed bed
conditions and less concern about crusting because
of the routine use of blind cultivation. Many annual
weeds have very small seeds that typically germinate
near the soil surface allowing termination and inhibition
of germination by blind cultivation. Blind cultivation
is much less effective in controlling annual weeds
that commonly germinate from > 2” and has almost
no effect on perennials. Emergence depths of some
common Midwestern weeds are shown in table 1.

Timing: Blind cultivation is often performed both preemergence and during the first several weeks postemergence before the crop is large enough for row
cultivation. Blind cultivation before crop emergence is
especially important for terminating early germinating

The OGRAIN (Organic Grain Resource and Information Network) program provides resources and support for new, transitioning, and
experienced organic grain farmers in the upper Midwest. OGRAIN is housed in the Organic and Sustainable Agriculture Research and Extension
Program within the UW-Madison Department of Plant Pathology under the leadership of associate professor Dr. Erin Silva. To contact us, email
emsilva@wisc.edu, call (608) 890-1503, or visit ograin.cals.wisc.edu.

Fact Sheet Series 22-2

Blind Cultivation for Early-Season Weed Control in Organic Grains

Table 1. Emergence Depth for Common Midwestern Weeds
OPTIMUM
EMERGENCE DEPTH

NOTES

FOXTAIL

0.5-2.0”

Gemination from greater depths is poor and negligible below 4” (3)

VELVET LEAF

0.5-1.0”

Variable emergence at 2-3” and rare below 3” (3)

COMMON LAMBSQUARTERS

0.1-0.2”

Few seedlings emerge from deeper than 1.2” (3)

COMMON RAGWEED

1.0-2.0”

Some can emerge from 3.1”, none emerge below 4” (3)

GIANT RAGWEED

0.5-2.0”

Many can emerge from 4” but none from 8 inches (3)

WATERHEMP

1” or less

Estimated based on seed size and related species (no direct studies, [3])

REDROOT PIGWEED

0.2-0.8”

Studies show a range of optimum emergence depths (3)

weeds in soil firmed during the planting operation
(e.g., planter tractor wheel tracks and row zones). It is
also a prime opportunity for controlling in-row weeds
with minimal risk to the crop and is considered by
many the most important timing for blind cultivation.
Blind cultivation is also valuable post-emergence
when the crop is better anchored and more tolerant
of mechanical impact than very young weed seedlings
and when germination of weeds can be delayed by a
loose dry soil surface zone (sometimes called a dust
mulch). It is important to pay attention to both crop
stage and weed stage because if the weeds are too
well anchored, it may not be worth the risk of damage
to the crop.
Blind cultivation is most effective against shallowrooted weeds when they are in the white thread stage
(see photo) and decreasingly effective each day after
weed emergence. Weeds in the white thread stage
are not readily visible, and their growth is controlled
by environmental conditions rather than the calendar
so the best way to know when weeds are at this
critical stage is to look for them by scratching the soil
surface. Once weeds are past the white thread stage,
they become increasingly resistant to termination by
blind cultivation, so it is wisely stated that “one day
early is better than one day late”. It is also important
to note that if too much time passes between blind
cultivation and crop emergence, the next flush of
weeds may occur when the crop is brittle or poorly
anchored and thus more sensitive to damage during
blind cultivation. Some farmers target the first blind
cultivation ~ 3 days after planting and a second pass
shortly before crop emergence but many farmers
only do 1 pass shortly before emergence. Since blind
cultivation normally obscures the tracks from the
planting operation, additional passes prior to crop
emergence are unguided unless GPS guidance or tracks

strategically left by modified equipment are available.
In summary, blind cultivation is most effective when
weeds have germinated but not yet emerged and
weather conditions promote rapid soil drying but many
farmers have observed significant benefit with less
than optimal weather conditions and rules of thumb
(first blind cultivation ~3 days after planting) should be
adjusted based on timing of pre-plant tillage and weed
and crop growth stage.
Weeds mostly in the white thread stage

Photo credit: Matron of Husbandry. Available at https://
matronofhusbandry.wordpress.com/2011/06/24/dontfear-the-weeds/

Soil conditions: Blind cultivation is most effective when
the zone of soil disturbance is intensively fractured
causing white thread weeds to become disconnected
from moist soil and rapidly desiccate. This is easiest
to achieve when the soil has good tilth and has dried
after a rain, creating a surface crust that is shattered
during blind cultivation. If soil is too wet during blind

Fact Sheet Series 22-2

Blind Cultivation for Early-Season Weed Control in Organic Grains

cultivation, the soil will not fracture properly and tractor
wheel tracks will not be removed, resulting in more
germination of weeds in the tracks. Surface roughness
(e.g., small ridges and valleys) can increase the action
of blind cultivation tools because they tend to have a
leveling effect, but excessive cloddiness will impede
their effectiveness. Residues incorporated in the zone
of soil disturbance can increase the action of blind
cultivation tools but can also cause plugging or raking
to occur if the blind cultivation tool is not designed for a
high residue environment.

EQUIPMENT AND CROP-SPECIFIC
RECOMMENDATIONS FOR BLIND CULTIVATION
The tools most commonly used for blind cultivation are
discussed in detail in the following sections:

Key factors impacting the performance of
tine weeders
Tool design and operation: Tine weeders (also called
tined weeder, flex-tine weeder, weeding harrow, or
flexible harrow) have flexible, narrow-diameter tines
(typically 5-8mm) mounted on bars (typically 1 or 2
tines per foot of bar width) that are grouped into gangs
(typically 3-8 bars each spaced ~ 12” apart). Each gang
has 9-12 off-set tines per foot of gang width (1-1.5”
between points of soil contact). Multiple gangs are
attached on a tool bar that is normally designed to fold
if the total width is greater than 10’.
Tines are made of spring steel and vibrate side to
side as they are pulled through the soil (typically
1-2”deep). This action terminates very young weeds
by a combination of desiccation and burial. It also
creates a loose zone of surface soil that is unfavorable
for germination and capillary rise. The aggressiveness
of soil fracturing is adjusted by changing the contact
angle of the tine tips, changing the down pressure on
the tines (by adjusting the height of the gangs and/or
tension on the springs) and by changing ground speed
(5). Adjustability makes tine weeders more versatile
than other types of harrows (6). Tine weeders work
best in loose or lightly crusted soil and perform well
in stony soil. Abundance, size and moisture content of
residues reduce flow through tines and can result in
raking (1,2). Models with fewer tines per lateral foot and
greater spacing between bars allow more residue flow.

Over time, the tine tips tend to sharpen. Sharpened tips
cause more damage to crops and less lateral fracturing
of soil. Sharpened tips can be clipped off, but other
parameters will need to be adjusted to achieve the
same performance with shorter tines.
Tine characteristics and gang attachment on the
tool bar both impact the action of a tine weeder.
The springiness of the tines increases as tine length
increases and decreases as tine diameter increases,
but also depends on type of steel and coil design. Most
often the tine tips are bent at angles ranging from 45°
to 85° but straight tines are also available. Tines with
45° tip angles are good for most situations and work
well with corn and soybeans. Tines with 85° tip angles
penetrate deeper, which can work well with taprooted crops like soybeans but can be too aggressive
for crops with a fibrous root system like corn and small
grains. For small grains, 45° to 60° tip angles work
best while 85° tip angles tend to uproot them. Stiff
straight tines can effectively bury weeds but can also
bury crop seedlings and are more appropriate for use
pre-emergence. Rigid mounting of gangs on the tool
bar results in more aggressive action while suspension
from chains is gentler on crops. Tine weeders are
typically operated between 4 and 8 mph but optimal
speed varies depending on tool design and setting, soil
conditions and crop growth stage.
Tine Weeding Pre-Emergence

Photo credit: Joel Gruver

Crop considerations: Tine weeders are most
commonly used for corn, soybeans and small grains,
with crop-specific adjustments (e.g., timing and depth
of tine penetration) needed to maximize weed control

Fact Sheet Series 22-2

Blind Cultivation for Early-Season Weed Control in Organic Grains

Table 2 . Tine weeding condations for soybean by crop stage and weed stage.

WEED STAGE

BEFORE
EMERGENCE

CROOK

White thread

Not advised

SPEED
TINE AGGRESSIVITY

COTYLEDON

1ST
UNIFOLIATE

1ST
TRIFOLIATE

4-8” TALL

White thread until 2-3 leaves

Not advised

5-7 mph

1 mph

2 mph

3 mph

4 mph

Moderate-high

Low

Low-moderate

Moderate

High

Moderate

Low

DAMAGE TO CROP

None-low

High

8-20” TALL

High

Adapted from (7) by Vereecke and Gruver.
Table 3. Tine weeding recommendations for corn by crop
stage and weed stage

WEED STAGE
SPEED
TINE
AGGRESSIVITY
DAMAGE TO
CROP

BEFORE
EMERGENCE

COLEOPTILE
to 2 LEAVES

White thread

Not advised

3-4
LEAVES

4-6
LEAVES

White thread until
2-3 leaves

5-7 mph

2 mph

2-3 mph

Moderatehigh

Low

Lowmoderate

None

Low to
high*

Leaf
tearing

Adapted from (7) by Vereecke and Gruver. *Depending on
rooting depth.

and minimize crop damage. Timing recommendations
for corn and soybeans based on crop stage and weed
stage are provided in Tables 2 and 3. It is important
to consider both crop stage and weed stage because
if weeds are too established, it is difficult to achieve
a desirable balance between weed control and crop
damage. Tine weeding of soybeans during their fragile
crook stage normally causes major stand loss, but final
populations < 100k may be considered acceptable by some farmers if a high level of weed control is achieved. After soybeans have well developed taproots, they are surprisingly tolerant of aggressive tine weeding but some soybean varieties are more tolerant than others. Corn plants are most fragile from emergence to the 2-leaf stage. Larger corn plants are more robust but plants knocked over or partially buried during tine weeding are unlikely to fully recover. As a result, some farmers only use tine weeding pre-emergence in corn. Soil conditions: Tine weeders can perform well in stony soils but hard crusts are problematic. When residue is moist, too abundant or poorly sized, tine weeders tend to rake residues. Soils with good tilth allow optimal soil crumbling and flow during tine weeding. Timing: Ideally, the first pass with a tine weeder is timed so that the next flush of weeds doesn’t emerge before a) the next blind cultivation OR b) when the crop is in a stage that is especially vulnerable to damage during blind cultivation (Tables 2 and 3). Some growers recommend waiting to perform the first pass until a few weeds have emerged. Tine weeding while crops are in a vulnerable stage requires careful consideration of the desired balance between weed control and crop damage. Key factors impacting the performance of rotary hoes Tool design and operation: Most rotary hoes have 1 or 2 rows of rotating spoon wheels comprised of 16 spokes with spoon shaped tips commonly referred to as “spoons.” The spoons penetrate, fracture and flick out soil and small weeds as they rotate (5) but are less likely to damage or bury crops than tine weeders. The wheels are generally 3 inches apart and spoons penetrate the soil surface approximately every 2 inches as they rotate (8). Rotary hoes are typically set to penetrate ~2 inches but some farmers routinely target deeper penetration. Surface residues can plug spoon wheels, but models are available that can handle high levels of residues without plugging (2,5). Spoons become narrower as they wear and must be replaced or rebuilt to maintain the action of newer spoons (9). Some farmers follow a schedule for replacing spoons (e.g., every 3000 acres). Penetration can be increased by the addition of helper springs that double downpressure from 18 to 36 lbs (10). Fact Sheet Series 22-2 Blind Cultivation for Early-Season Weed Control in Organic Grains Crop considerations: Rotary hoes are commonly used for corn, soybeans and cereal grains. Timing recommendations based on crop stage and weed stage for corn and soybean are provided in Tables 4 and 5. Rotary hoeing of soybeans during the fragile crook stage can cause significant stand loss but this may be an acceptable trade-off if good early season weed control is achieved. Post-emergence hoeing of corn is less likely to cause crop damage than tine weeding. Soil conditions: Rotary hoes can perform well on crusted soils, but stony soils are problematic. Stones can damage spoons and also can cause wheels to jam and drag which will cause major damage to crop rows if the jammed wheel is located in a row. When soil is too wet, a rotary hoe may just poke holes. When soil is too hard, it is difficult to achieve adequate penetration. Timing: Rotary hoes are most effective when weeds are in the white thread stage. Timing is critical because after emergence, many weeds will survive rotary hoeing unless the hoe is operated more aggressively. Options for increasing control of emerged weeds include: shattering a dry crust formed after an intense rain, surface roughness that is leveled during hoeing, greater depth of penetration, higher ground speed (keeping in mind that excessive speed can cause skipping) and double hoeing in opposite directions. Rotary Hoeing Post-Emergence Photo credit: Joel Gruver CONCLUDING THOUGHTS Intensive use of blind cultivation is a common thread connecting many organic farmers who are recognized for effective weed management. These farmers generally plant high initial populations and are willing to accept significant stand loss (especially soybeans) in pursuit of a high level of early season weed control. They tend to perform blind cultivation a day early rather than a day late and modify and upgrade their tools to maintain aggressive action. They often combine the use of multiple tools. For example, tine weeders and rotary hoes are discussed separately here but many farmers own both and use them in sequence (e.g., tine weed pre-emergence but rotary hoe postemergence in corn). Also, if the first row cultivation Table 4. Rotary hoeing recommendations for soybean by crop stage and weed stage BEFORE EMERGENCE WEED STAGE SPEED DAMAGE TO CROP CROOK COTYLEDON White thread 1ST UNIFOLIATE 1ST TRIFOLIATE 4-8” TALL 8-20” TALL White thread until 1-2 leaves Not advised 9-12 mph <6 mph 6 mph (max) 7-9 mph 9-12 mph None Moderate-high Moderate-low Very low None Adapted from (7) by Vereecke and Gruver. Table 5. Rotary hoeing recommendations for corn by crop stage and weed stage BEFORE EMERGENCE WEED STAGE SPEED DAMAGE TO CROP COLEOPTILE 1-2 LEAVES White thread 3 LEAVES 6-7 LEAVES White thread until 1-2 leaves 9-12 mph 6 mph 6 mph (max) 7-9 mph None Moderate to high Moderate Low Adapted from (7) by Vereecke and Gruver. 4-5 LEAVES 9-12 mph Very low Stem breakage Fact Sheet Series 22-2 Blind Cultivation for Early-Season Weed Control in Organic Grains occurs when the crop is still small, some farmers follow with a blind cultivation pass that shatters soil from weed roots and improves the effectiveness of the row cultivation. In conclusion, blind cultivation is both a DIRECT and INDIRECT weed control tactic that can be highly effective when used at the right time and aggressiveness to achieve early season weed control within a soil tilth building cropping system. Tine Weeder vs Rotary Hoe • Timing: Timing is more critical with a rotary hoe because the rotating action is typically less effective at removing emerged weeds than the continuous dragging action of a tine weeder. • High surface residue: Residue can pose a challenge for both tools, but the rolling action of a rotary hoe is less likely to plug than the dragging action of a tine weeder and high-residue rotary hoe models are available. • Soil types: Rotary hoes perform better on crusted soils than tine weeders. Tine weeders perform better in stony soils than rotary hoes, which are more likely to get damaged or jammed by stones. • Ground speed: Rotary hoes are typically operated 1.5 – 2x faster than tine weeders. • Overall performance: Tighter spacing of soil contact points (1-1.5” vs. 3”) and continuous soil contact (vs. penetration approximately every 2”) enables tine weeders to operate more aggressively and generally control more weeds than rotary hoes (6). One study found that tine weeding provided 80-90% weed control vs. ~80% for rotary hoeing; however, both methods can have variable results, with weed control as low as 2030% (11). REFERENCES & FURTHER INFORMATION Resources and videos in bold are especially recommended for further information 1. Mohler CL, Teasdale JR, DiTommaso A. Manage Weeds on Your Farm: A Guide to Ecological Strategies. College Park: Sustainable Agriculture Research & Education [SARE]; 2021. (SARE Handbook Series 16). 2. Gunsolus J, Wyse D, Moncada K, Fernholz C. Weed Management. In: Risk Management Guide for Organic Producers. University of Minnesota; 2010. p. 6-1 - 6-24. 3. Martens K, Martens MH. Look, Ma! No Weeds: Early Season Weed Control [Internet]. The New Farm. 2005 [cited 2022 Oct 10]. Available from: https://cpbus-e1.wpmucdn.com/blogs.cornell.edu/dist/e/4211/ files/2014/04/Cultivation-sahdli.pdf 4. Mallory EB, Gallandt ER. Blind Cultivation for Weed Control in Small Grains - Cooperative Extension: Grains, Pulses & Oilseeds - University of Maine Cooperative Extension 5. 6. 7. 8. 9. 10. 11. [Internet]. Cooperative Extension: Grains, Pulses & Oilseeds. [cited 2022 Oct 27]. Available from: https://extension. umaine.edu/grains-oilseeds/topics/blind-cultivationweed-control-small-grains/ Bowman G, editor. Steel in the field: a farmer’s guide to weed-management tools. Beltsville, Md: Sustainable Agriculture Network; 1997. 128 p. (Sustainable Agriculture Network handbook series). Tine Weeders [Internet]. Practical Farmers of Iowa; 2019 [cited 2022 Oct 10]. Available from: https://www. youtube.com/watch?v=uenCN22Oxjs Alamome D, Garnier JF, Moulin V, Prieur L, Rodriguez A, Arvalis CV. Désherber mécaniquement les grandes cultures. Mars 2021. Institute Technique de L’Agriculture Biologique; 2012. (Programme CASDAR). Rotary Hoes [Internet]. Practical Farmers of Iowa; 2019 [cited 2022 Oct 10]. Available from: https://www. youtube.com/watch?v=E5YIWo-LBXk Ho-Bit jig basics - YouTube [Internet]. [cited 2022 Nov 30]. Available from: https://www.youtube.com/shorts/jsj9ylcr-A Yetter Equipment [Internet]. J.O. Harris Sales L.L.C. [cited 2022 Nov 30]. Available from: https://www.joharrissales. com/organic-farming-equipment/yetter-equipment Gallandt ER, Brainard D, Brown B. Developments in Physical Weed Control. In: Integrated Weed Management for Sustainable Agriculture. Cambridge, UK: Burleigh Dodds Science Publishing Ltd; 2018. p. 261–83. Authors Joel Gruver1, Claire Stedden2, Léa Vereecke3, Erin Silva4 1. Professor of Soil Science and Sustainable Agriculture, Western Illinois University; 2. Outreach specialist, OGRAIN program, University of Wisconsin – Madison; 3. Organic Farm Consultant and Regional Manager, Rodale Institute; 4. Associate Professor, Organic and Sustainable Cropping Systems Specialist, University of Wisconsin – Madison Factsheet 22-2. Released January 15, 2023 For more information, visit ograin.cals.wisc.edu, email emsilva@wisc.edu or call (608) 890-1503. The OGRAIN program provides resources and support for new, transitioning, and experienced organic grain farmers in the upper Midwest. OGRAIN is housed in the Organic and Sustainable Agriculture Research and Extension Program within the UW-Madison Department of Plant Pathology under the leadership of associate professor Dr. Erin Silva. We host a variety of events, support a producer listserv (join by emailing join-ograin@lists.wisc.edu) and provide resources for organic grain farmers.