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Pacific Northwest
Conservation Tillage Handbook Series No. 23
Chapter 2 - Conservation Tillage Systems and Equipment, May 1999
Direct
Seeding or No-Till....
What's the Difference?
Authors: Roger Veseth,
WSU/UI Extension Conservation Tillage Specialist, Moscow, ID; and Russ
Karow, OSU Extension Cereal Specialist, Corvallis, OR.
Direct seeding is
becoming a commonly accepted term across the Northwest and around the
world. The Northwest Direct Seed Cropping Systems Conferences in 1998
and 1999 each drew audiences of about 900 compared to 200-350 for similar
NW no-till and conservation tillage conferences over the past 25 years.
Is direct seeding that much different?
Well, yes and no.
YES in that dramatic improvements in crop management and equipment technologies
compared to 20-30 years ago and (here in the U.S.) new cropping flexibility
under the USDA farm program can greatly increase the success of these
planting systems today compared to some difficult times with "no-till"
in the past. We also now have a much better understanding of soil quality
and productivity benefits and potential for improving production efficiency
than in the past. Soil erosion control is becoming an important side benefit
of more productive, more profitable farming systems.
And now the NO part.
It is largely semantics. Direct seeding is, for the most part, just a
"new improved" term for no-till planting systems, but it does
provide the opportunity for more accurate descriptions of the actual planting
systems and seedbed conditions. Now let's get into the meat of the discussion.
Traditional
Tillage Systems Terminology
Tillage system terminology
can get confusing, but keep in mind that the end results - erosion control,
soil quality and productivity, production efficiency and profitability
- are the important factors. Don't get too side-tracked on terminology.
The Conservation Technology Information Center coordinates annual national
surveys of tillage practices across the U.S. and has defined several categories:
No-till
- Soil is left undisturbed from harvest through planting except for strips
up to 1/3 of the row width
Mulch-till
- Full width tillage which disturbs all of the soil surface prior to or
during planting and retains 30% or more surface residue cover
Conservation
tillage - Umbrella term for the above tillage systems which maintain
30% or more residue cover
Reduced-till
- Tillage systems that leave 15-30% residue cover
Intensive-till
or conventional-till - Tillage systems that leave less than 15%
residue cover
Tillage definitions
help, but there are lots of "gray areas" when it comes to fitting
the wide range of equipment options and final field conditions into these
definitions. Although the term "no-till" has been used for more
than three decades, there is still confusion about what planting systems
are included or excluded. Some no-till drills are so low disturbance that
it can difficult to see where they have seeded - examples of "true
no-till or zero-till" systems. In contrast, some one-pass, "no-till"
implements might be better described as a "till-plant" systems
because they result in substantial soil disturbance and residue burial.
What we have today are a wide range of high- to low-disturbance "no-till"
systems, which may seem like somewhat of a contradiction of terms.
The term direct seeding
has evolved, in part, to more effectively describe the planting process
and end results, and this is one reason why it is becoming an increasingly
common term worldwide. It tends to be a more flexible and inclusive term
rather than exclusive, allowing more grower and industry innovation. This
flexibility can help to overcome practical challenges in residue and pest
management as we move towards the transition to low-disturbance direct
seed / no-till - which offers the greatest long term potential benefits
in erosion control, soil quality and productivity, water conservation,
energy efficiency, and production efficiency. The "newer" term
of direct seeding can also help get past the "baggage of past failures"
associated with no-till, emphasizing that many advances in crop and pest
management technologies, equipment, and products now make it a "new
ball game." There are some variations of direct seed systems that
do not fit in the traditional definition of no-till, and when they do
not, those differences need to be described. So, direct seeding is not
just a new name for the same old practice, but a new name to reflect new
management technologies and systems that are now available and will continue
to be improved.
Direct Seed
Systems Definitions
As the name indicates,
all direct seed systems have at least one important factor in common -
that there is no traditional "full width" tillage for seedbed
preparation with field cultivators, or other secondary tillage implements
prior to planting. To most effectively describe the planting process and
final seedbed conditions, direct seeding should be further categorized
into high- to low-disturbance, and one- or two-pass systems. The following
are descriptions of some common types or variations of direct seed systems
today.
Low-Disturbance
Direct Seeding
Narrow knives, single
discs or double discs (standard or offset with one leading edge) only
disturb a narrow strip of soil between openers retaining nearly all of
the residue on the surface. This would be the same as the traditional
"no-till, zero-till or slot-till" definitions.
High-Disturbance
Direct Seeding
Hoe or sweep openers
disturb more of the soil between openers, though usually not full-width,
and still retaining much of the residue on top. With some flatter sweep
blades, the surface soil and residue disturbance can be minimal even though
much of the surface layer is undercut with the opener. Obviously, the
furrow size, soil disturbance and residue retention will vary with opener
designs, speed, soil moisture and other factors.
One-Pass
or Two-Pass Direct Seed Systems
Growers can choose
between one-pass direct fertilize and seed systems, and two-pass systems
with direct fertilizing and direct seeding in separate operations. In
both cases, there are no other tillage operations for seedbed preparation
before seeding. The choice depends on the precipitation zone and seasonal
distribution, length of planting windows, equipment availability and cost,
crop choices, available labor, and a number of other consideration. There
are a number of "direct-shank" fertilizer applicators for fertilizing
without prior tillage. Some can be very low disturbance, such as narrow
shanks or knives, coulter-knife combinations, coulter - pressure injection
and spoke wheel applicators. In some lower and intermediate rainfall areas,
direct fertilizer application in the fall before direct seeding spring
crops is becoming increasingly common, helping to improve nitrogen availability
to the crop in our dry PNW spring / summer environment. The one-pass and
two-pass systems could result in similar soil and residue disturbance
in the final seedbed if the similar fertilizer and seed openers are used
in both systems. Two differences that could have agronomic effects would
be that the one-pass system has 1) more precise positioning of the deep
band fertilizer in relation to the seed row, and 2) may have soil disturbance
from the fertilizer opener below the seed-row (depending on the fertilizer
opener type and configuration), both of which can increase plant tolerance
to root diseases in higher root disease situations (e.g. cereals after
cereals).
Example
Systems - To help others understand your direct seed system,
you should use the above "descriptive categories" that best
fit your system. Two examples are one-pass, high-disturbance direct seed
systems, and two-pass, low disturbance direct fertilize and direct seed
systems. You could also add other descriptors that help improve the understanding
of your system, such as two-pass, low disturbance, fall direct fertilize
- spring direct seed systems. These types of descriptions are definitely
longer and more cumbersome than saying "no-till," but it makes
for much better communications.
A Hybrid
"Till-Direct Seed" Category
Fall Mulch-till
- Spring Direct Seed (also know at the Stale Seedbed) - This is one
type of "direct seeding" that does not fit the typical "no-till"
definition because of full-width tillage between harvest and planting.
In the world of tillage definitions, this is categorized as "Mulch-till."
It needs to be pointed out that these fall mulch-till - spring direct
seed systems will not achieve improvements in soil quality that are possible
with direct seeding alone. However, it is a big step in the right
direction. For some growers that struggle with heavier residue levels,
wet cold spring conditions, or other production challenges in the higher
rainfall, annual cropping regions, a combination of mulch-till in the
fall and direct seeding of spring crops without spring tillage
can provide an opportunity to begin the transition into lower disturbance
direct seed systems for spring crops. As new crop rotation and residue
management technologies become available to deal with the heavy crop residue,
growers can begin to phase out the fall tillage component and move into
continuous direct seed systems. Compared to mulch tillage systems with
both fall and spring tillage before spring crops, this "hybrid"
system offers the potential for significant improvements in residue retention
for erosion control and water conservation and reduced soil compaction
from spring tillage operations on wet soils. Obviously, there will also
be some corresponding improvements in soil quality, but less than with
direct seeding alone.
Can You
Be a Partial Direct Seed Farmer???
Another yes and no
answer. But, there are actually two questions to answer. First on a field
basis and second on a farm basis.
No... on
a Field Basis
Continuous direct
seeding is the only way to reap the full soil improvement benefits from
direct seeding. Using intensive tillage at any time in the rotation cycle
disrupts the improvements in soil organic matter content, macroporosity
and other soil productivity factors that take time to build and for you
to see the benefits. HOWEVER, from a
practical standpoint, if you don't have the equipment, crops diversity,
residue management options, etc. needed for continuous direct seeding
now, using mulch-tillage intermittently with direct seeding in your rotation
is much better than continuous mulch-till or more intensive tillage.
Tillage results in
increased soil oxygen levels and higher soil temperatures that stimulate
intense microbial decomposition of soil organic matter and the resultant
release of soil carbon as carbon dioxide. Soil organic matter is biologically
burned off faster with intensive tillage than it can be built through
the addition of new crop residues under our current dryland cropping systems
with intensive tillage. Organic matter is a critically important soil
component directly related to soil fertility, water holding capacity and
infiltration, aggregation and structure, erodibility, biological activity
and a long list of other soil properties affecting soil productivity and
soil quality. Recent research shows that continuous direct seeding systems
offer the greatest potential for increasing soil organic matter content
over time.... now commonly termed "carbon sequestration" under
the topic of global warming. The less severe and less frequent the soil
disturbance, the greater the carbon accumulation potential.
In addition to organic
matter, another important related soil quality benefit of continuous direct
seeding is the improved soil macroporosity. That refers to the proportion
of larger soil pore spaces for water and air movement created by undisturbed
root channels, earthworm holes and other soil fauna. Full-width tillage
breaks the continuity of these soil pores and eliminates or greatly reduces
their effectiveness. In a long-term tillage near Pendleton, OR, researchers
found that rates of water infiltration (inches/hour) into the soil were
0.04 in the plow-conventional tillage treatment, 1.1 after the first year
of direct seeding, and 5.1 after 16 years of direct seeding. That's a
pretty dramatic difference in the potential for water runoff and evaporation,
and storage for crop use. Part of this improved soil structure is also
attributed to increased microbial activity associated with higher organic
matter content and increased soil water near the surface without tillage
- increasing soil aggregation and "tilth," as well as fertility.
Yes.... on
a Farm Wide Basis
Being a direct seed
farmer does not mean you need to direct seed your entire farm from the
start. Successful direct seeding and more intensive cropping takes time
to gain the knowledge and experience to develop management systems that
are best adapted to your farming conditions. We would encourage you start
on a few fields rather than the whole farm and gradually increase the
acreage with increased confidence. Realize that you will probably have
to learn from your mistakes, or at least learn what works and what doesn't
on your fields. Remember that equipment and crop performance will likely
change with improvements in soil quality over successive years in the
transition to direct seeding
If you can afford
to keep a set of your current tillage and planting equipment as well as
a direct seeding drill, or rent a drill from a neighbor, local dealer
or conservation district, then it makes sense to utilize both systems
while you are working your way through the learning curve and transition
to direct seeding. This is especially true given current economic conditions
and the ever changing weather.
Think
of Your Fields like a Financial Investment Systems - You
can keep some of your fields in "certificates of deposit - CDs"
under your current, generally-reliable tillage / rotation system where
you get a known rate of return. Put some of your field in higher-yielding
"bonds" while you explore new cropping systems using direct
seeding where you know it will work in the rotation, but still have the
option of mulch-till where needed in the rotation as well. A new cropping
example for the crop-fallow region could be flex-cropping, or recropping
part of your winter wheat stubble acreage in the spring by direct seeding
spring crops when there is adequate soil moisture, markets, and weed levels
permit, but fallowing if spring planting is not feasible. Similarly, you
could also direct seed winter wheat following spring crops on part of
your farm when there are early fall rains and other economic and agronomic
factors were favorable. You would need to be prepared both mentally and
financially to not plant some fields in the spring or fall when it will
not make sense to do so. And finally, put some of your field in the "stock
market" - continuous direct seeding using more diverse and intensive
rotations to make it work - where you have potential for the greatest
long term and short term gains, but where you are also at a higher level
of risk early on the learning curve. As you gain experience, you can add
more fields into this investment area with the greatest potential. Fortunately,
unlike in the stock market, your risk level will continue to decline with
additional years of experience with direct seeding and more intensive
cropping, and with continued advances in production technologies. The
weather is obviously always an unpredictable factor to keep in mind.
Define YOUR
Direct Seed Systems
Direct seeded acreage
and the number of growers working in direct seed systems is rapidly increasing
worldwide. It is important to continually explore new research technologies
and learn from experiences of other direct seed growers because these
are rapidly evolving farming system. Direct seeding and flexible intensive
cropping will require more information on a field-by field basis and greater
communication with input providers and landowners to be successful. You
will need to decide what crops to plant in which fields based on markets,
field history, field moisture status, weed and disease problems, and how
to manage those problems under direct seeding.
Every grower has
different production conditions and different experiences with direct
seeding, and everyone can benefit from sharing these experiences. One
key to effective sharing will be more accurate descriptions of the direct
seed systems being used. The same is true for researchers, who need to
give detailed descriptions of the treatments and production conditions
with the research results so that others can more easily adapt the results
to different farming conditions and different equipment. Fertilizer placement,
seed and fertilizer opener types, row spacing, packer type, crop rotations,
residue amounts and management, growing conditions and many other factors
can effect the performance of a direct seed system and need to be carefully
defined for the benefit of others. Everyone will benefit from improved
descriptions of direct seed cropping systems.
Pacific Northwest
Conservation Tillage Handbook Series publications are jointly produced
by University of Idaho Cooperative Extension System, Oregon State University
Extension Service and Washington State University Cooperative Extension.
Similar crops, climate, and topography create a natural geographic unit
that crosses state lines in this region. Joint writing, editing, and production
prevent duplication of effort, broaden the availability of faculty, and
substantially reduce costs for the participating states.
The Pacific Northwest
Conservation Tillage Handbook is a large, three-ring binder handbook
that is updated with new and revised Handbook Series publications. It
was initiated in 1989 as a PNW Extension publication in Idaho, Oregon
and Washington. Updates to the Handbook are provided when the updating
card is returned. By 1999, 47 new PNW Conservation Tillage Handbook Series
have been added to the original 98. Copies of the complete Handbook are
available for $20 through county extension offices in the Northwest or
ordered directly by calling state extension publication offices: Idaho
-- (208) 885-7982; Oregon -- (541)-737-2513; Washington
-- (509) 335-2999 (some shipping and handling charges and sales tax may
apply). It's now accessible on the Internet! All of the PNW Conservation
Tillage Handbook and Handbook Series are being put on the
Internet home page (http://pnwsteep.wsu.edu) Pacific Northwest STEEP III
Conservation Tillage Systems Information Source. The home page also contains
recent issues of the PNW STEEP III Extension Conservation Tillage
Update, listings of other conservation tillage information resources,
coming events and much more. For more information on the Handbook or updates
to the Handbook, contact Roger Veseth, WSU/UI Conservation Tillage Specialist,
Plant Soil and Entomological Sciences Department, University of Idaho,
Moscow, ID 83844-2339, phone 208-885-6386, FAX 208-885-7760, e-mail (rveseth@uidaho.edu).
Cooperative Extension
programs and policies comply with federal and state laws and regulations
on nondiscrimination regarding race, color, gender, national origin, religion,
age, disability, and sexual orientation. The University of Idaho Cooperative
Extension System, Oregon State University Extension Service and Washington
State University Cooperative Extension are Equal Opportunity Employers.
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