Unit 12: Tillage &
Farming Systems
Chapter 12
Objectives
Historical trends in tillage
 Investigate reasons for tillage
 Different types of tillage
 Advantages/impacts of alternative tillage
management
 Role of organic farming
 Uses & issues of transgenic crops

Purposes for Tillage
Evolution of tillage:
 Minimum
tillage in primitive times – all hand
work
 As equipment became available – tillage
increased to maximum tillage – now
considered excessive & wasteful
 Now going back to moderate – minimum
tillage – fuel savings, healthier for soil,
reduced labor costs, additional technologies
for control of various yield reducers, better
understanding of soils
Purposes for Tillage

Seedbed Preparation
 Most
needed when planting small, high-cost
seed (lettuce, clover)

Less critical for vigorous, larger seeds (corn,
wheat, soybeans)
 Should
be prepared according to preference
of the crop being seeded
Alfalfa – fine, firm soil, shallow seeding depth
 Wheat – dry, aerated soil, good infiltration &
aeration

Purposes for Tillage
 Tillage

incorporates crop residue
Difficult to plant through much residue
Seed may be left in residue, not in soil
 Seed likely to die
 Poor, erratic stand


Weed Control
 Weeds
compete for soil water, nutrients, light
 Tillage essential to deter weeds

Especially before herbicides
Purposes for Tillage
– herbicides more effective at
controlling weeds than tillage
 Today

Also:
Eliminate field passes
 Preserve soil moisture
 Reduce damage to crop roots

 Less
developed countries = more hand
tillage/cultivation
 Farmers prefer aesthetically pleasing fields
Purposes for Tillage

Loosening the Soil
 Excessive
tillage can cause extensive
compaction
Plow or Tillage Pan – zone of compaction just
below tillage zone
 Greatly decreased infiltration rates, aeration, root
penetration

 Need
corrective tillage to remedy, or
grasslands
Purposes for Tillage

Shaping the Soil
 Flood
& Furrow irrigation
 Tillage forms ridges & furrows, and smoothes
soil surface
 Allows water to move equally through field for
irrigation
Purposes for Tillage

Incorporation of Lime & Fertilizer
 Increases
effectiveness and volatility of
materials

Control of Insects & Disease
fly – plow infested wheat stubble
 Corn Borer – burying infests stalks
 Grasshoppers, etc.
 Hessian
Purposes for Tillage

Improving Water Relations
 Break
soil crusts, loosens soil, increases
infiltration
 Storage of even a little more water can be
difference in profitable/unprofitable yields
 Using subsoiler that leaves soil surface w/
little disturbance may increase water storage
3” through winter
Purposes for Tillage

Aerating & Warming
 Compacted,
crusted soils have poor air
exchange
 Limits root growth, plant productivity
 Poor microbe efficiency
 Can speed temp warming, if desired (early
spring planting)
 Dries soil if excessively wet

What is the risk of working wet soils?
Purposes for Tillage

Reasons to Reduce Tillage or Eliminate
Tillage
 Must
keep food production economical for
producers & consumers
 Reasons to reduce tillage:

Eliminate/reduce erosion
Critical to keep topsoil in place for ag’s future
 Gov’t pressure/regulation will force more conservation
techniques

Purposes for Tillage

Save time/fuel
Conventional tillage uses ~7.7 gal/ac of fuel
 No-till consumes ~4.1 gal/ac fuel
 So: 3.6 gal/ac fuel savings * $2.75 diesel = ~$10/ac
* 1,000 ac farm = $10,000/yr
 Might this be difference in profit/loss?

 Potential
benefits of reduced tillage:
Improved air/water quality
 Decreased erosion
 Time
 Improved water storage in topsoil

Purposes for Tillage
Double cropping more profitable
 Fuel
 Decreased compaction
 Soil tilth, organic matter improvements
 Increased wildlife habitat

Tillage Terminology

Primary tillage – first & deepest tillage
operation
 Loosens
soil
 Moldboard plow, disc, chisel plow

Secondary tillage – follow primary tillage
 Disks,
cultivator, harrow
 Kill weeds, incorporate chemical/fertilizer
 Prepare seedbed
Tillage Terminology
Chisel – narrow shank pulled through soil
to rip
 Chisel plow – rips soil 6 – 12” depth
 Conservation tillage – any tillage system
that leaves >30% of surface covered by
residue for erosion control

Tillage Terminology

Conventional tillage – traditional
moldboard plow, disc, harrow, seeding
 Any
tillage leaving <15% of surface covered
by residue
Coulter – disk w/ straight/fluted edge for
slicing open soil
 Cultivator – small sweeps pulled between
crop rows to kill weeds

Tillage Terminology
Disk – combination gangs of concave
disks to till soil
 Harrow – vertical tines to break clods
 Mulch till – surface tilled, residue remains
 No-till – no tillage, except for seeding &
maybe fertilizer injection

Tillage Terminology

Reduced tillage – combination of tillage
operations
 >15%
<30% residue cover
Ridge till – ridges formed by sweeps, etc.
 Shovels – narrow-winged sweeps
 Strip till – small strips where seeds planted
tilled only

Reducing or Eliminating Tillage
Tillage started to improve on nature’s
methods of crop growth
 Ability
to grow more crop/land area
 Option to grow a single crop in a field

Physical Properties of Soil
 Any
traffic increases compaction
 Tillage loosens soil to depth of tillage, but
increases compaction on subsoil
Reducing or Eliminating Tillage
– increases #/size of soil pores, soil
protection & aggregation are improved w/
crop residue
 Reduced & conservation till fields cooler &
wetter in the spring
 No-till
Delays planting
 Reduces germination & early seedling growth

Reducing or Eliminating Tillage
 Earthworms
Improves population
 Greater positive effect on soil matrix

Water infiltration
 Soil aeration

 Deep
tillage
Still feasible to help open subsoil
 Rip at 12 – 16” depth
 Deep rooted crops can also help w/ compaction &
reduce tillage

Reducing or Eliminating Tillage
 Increases
organic matter
Organic matter % increases twice rate of increase
in conventional till (in upper 2”)
 No difference in organic matter below 6”
 Other studies say no increase in organic matter

 Increased

yields
Are we seeing that here?
Reducing or Eliminating Tillage

Seedbed Preparation
 Reduced
till – works well for large-seeded
crops

Fine-seeded crops prefer more tillage, w/
pulverized, uniform seedbed
 May
see decreased seedling emergence,
reduced stand density
Especially if you don’t have a planter able to get
through residue
 May use 10-15% more seed to compensate

Reducing or Eliminating Tillage

Pest Control
 Minimal
tillage increases burden of weed
control on herbicides
 Will increased herbicide usage delete
fuel/labor savings?
 Maximize crop rotation effects
 No-till may decrease weed stands long term
Don’t work weed seeds into soil during tillage
 Reduced ability for weed seed to germinate


They need the same seed/soil contact as crops
Reducing or Eliminating Tillage
 Increased
dependence on insecticides as well
More favorable environment to harbor them
 Bigger problem w/ soil insects, less opportunity to
disturb their life cycle

 What
other risks are there if we depend more
on chemicals for control of weeds/insects?
Reducing or Eliminating Tillage

Fertilizer & Lime Applications
 Reduced
tillage limits ability to incorporate P,
K, lime into the soil
 Can result in a concentrated zone of nutrients
in top 3” of soil
May be acidified by N
 May cause shallow rooting

Reducing or Eliminating Tillage

Organic Toxins
– toxins emitted by one plant
affected growth of another
 Allelopathy
Wheat on wheat
 Corn on corn ?

 Leaving
residue on the soil surface can
increase the risk of toxins
 Most injurious in early growth stages
Reducing or Eliminating Tillage

Special Situations
 Some

Have specific needs for tuber growth



crops won’t respond well to reduced tillage
Potatoes
Sugar beets
Can be more susceptible to disease

Strawberries/cucumbers & fungal diseases
 Excess


residue problematic for surface irrigation
Water not able to flow freely over soil surface
Furrows need to be clean for efficient flow & help reduce
erosion of ridges
Reducing or Eliminating Tillage

Erosion Control
 Greatly
decreased wind erosion w/ reduced
tillage
 Advances in chemical technology allows for
easier use of cover crops & burndown
 Slows ability of water to wash soil from
surface as easily
Farming Systems & Environmental
Quality
Reduced tillage increases dependence on
chemical control of pests

Typically increases pesticide use 15-40%
Erosion of N, P and pesticides increased w/
reduced tillage

Due to zone of accumulation nearer soil surface
than conventional tillage
Tillage itself is erosive
Farming Systems & Environmental
Quality
Carbon Sequestering – putting C back into
the soil
 Driven by global warming theory

 Elevated

levels of CO2
Soil used to/can be source of atmospheric
C
 w/
reduced tillage, becomes a recipient of
atmospheric C
Farming Systems & Environmental
Quality

Water Quality
 Studies
indicating reduced tillage reduces
water pollution risks
 Even though more polluters concentrated at
soil surface
 So, what else is driving this trend?
Transgenic Crops
GMO’s have drastically modified farming
practices & options
 Genetically Modified Crops
 Contains
genes from another organism
inserted artificially into a newly engineered
crop

RR soybeans

Weed control easier, more effective w/out damaging
beans
Transgenic Crops
 Bt
Cotton
Cotton resistant to the very damaging bollworm
 Insecticides often kill both damaging & beneficial
insects

 Bt
Corn
Bacillus thuringensis – protein that is toxic to the
corn borer
 Pollen from Bt corn found to be lethal to monarch
butterflies


Should it remain approved for use? Why?
Transgenic Crops

Risks Associated w/ GMO’s
 Potential
for herbicide resistant plant or pollen
to develop
 Difficulty controlling escape of GMO pollen
 Consumer concern over GMO grain entering
human food system
 Much debate over safety – no known health
risks to humans or animals
Transgenic Crops

Present Status & Trends
 Most
countries approve planting of GMO
crops
 Very little used in Japan, China, Europe
 Government concerns

Backlash from religious & environmental groups
 Company
risks
Fear gov’t’s inability to enforce contracts
 Loss of their technology to competition

Sustainable Agriculture & Organic
Farming

Sustainable Agriculture – minimal use of
resources (water, chemicals, energy) w/
little/no damage to environment
 Balance
of energy used vs. energy produced
 Crop selection: choose proper crops for
situation
 Crop production: proper agronomic
management w/ planting, cultivating, pest
management, harvest. Maximize crop
rotation benefits
Sustainable Agriculture & Organic
Farming
 Soil
fertility: use legumes & manure wisely,
use of commercial fertilizers sparingly, and
manage their effectiveness
 Soil conservation: minimal tillage for
acceptable field conditions
Use windbreaks, buffer strips, strip cropping when
necessary
 Minimize soil compaction
 Maximize crop residue use

Sustainable Agriculture & Organic
Farming

Objectives of Organic Farming
 Avoid
inputs of synthetic substances
 Produce healthy foods untainted by unnatural
substances
 Strategies:
Use of manure & legumes for plant nutrients
 Tillage, crop rotation, manual labor for weed
control
 Natural suppressants, repellants, & predators for
insect & disease control

Sustainable Agriculture & Organic
Farming

Mixed Reviews for Organic Farming
 Clearly

less environmental problems
Although may increase N loss to groundwater
 Some
decrease in energy use
 Food quality superiority unfounded
 20-45% reduction in yields (European study)

Increased demand for land, w/ decreased
output/ac
Sustainable Agriculture & Organic
Farming

Organic Food Marketing
 Sales
increasing sharply (especially in
wealthy countries)
 Fastest growing sector of world agriculture
 Large export market for countries w/ highest
% organic farming (Asia, Australia, Latin
America)

Ironic because of amount of fuel needed for
transportation
Sustainable Agriculture & Organic
Farming
 Gaining
Certified Organic Status
Land have no prohibited substances applied for 3
yrs before harvesting an organic crop
 Use of genetic engineering, ionizing radiation,
sewage sludge prohibited
 Fertility & nutrients managed through tillage,
cultivation, crop rotation, cover cropping,
supplemented w/ manure (limited synthetic
materials)

Sustainable Agriculture & Organic
Farming
Prefer use of organically grown seed
 Pests, weeds, diseases must be controlled through
management
 May only use approved synthetic substances

zero tolerance standards – slight
contamination (GMO’s) is allowed
 Restrictions also encompass food processors
 Livestock based organic production
restrictions differ from crop production
 No
Sustainable Agriculture & Organic
Farming
 Four
levels of organic labeling
100% organic – seal on package
 95-100% organic – seal on package
 70-95% organic – can claim organic, but no seal
 <70% organic – can list organic ingredients, no
organic claim or labeling

Assignment