Environmental Benefits of Cover Crops

Soil Erosion, Nutrient and Pesticide Reduction
Bob Broz - Extension Water Quality Specialist
205 Ag Engineering
[email protected]
Environmental Concerns
Associated with Agriculture
 Soil erosion
 Nutrient runoff
 Pesticide runoff
 Loss of habitat
 Other
Midwest Cover Crop Council
 Cover crops are an effective tool to reduce soil erosion
and increase nutrient recycling on farmlands, thereby
also decreasing the soil and nutrient loads entering
lakes and waterways. Cover crops can have numerous
other benefits including improvement of soil quality,
pest management, fertility management, water
availability, landscape diversification, and wildlife
 http://www.mccc.msu.edu/
Defining Cover Crops and their
Benefits to the environment
 Cover crops are grown to protect and improve the soil,
not to harvest. Cover crops have the potential to
improve soil tilth, control erosion and weeds, and
maintain soil organic matter. They can reduce
compaction and increase water infiltration which
decreases leaching of nutrients. Cover crops retain and
recycle plant nutrients (especially nitrogen) between
crops, provide habitat for beneficial microorganisms,
and increase plant diversity.
How do we define cover Crops
 Not just your grandfather's cover crops
 Wheat
 Clover
 Rye
 Crops that are:
 Grown between cash crop cycles
 Intercropped with cash crops to cover bare ground
 Planted in the absence of normal crop
 Grown primarily to add organic matter and nutrients
 Selection of a cover crop depends on when it can be
planted and the goal for its use. Legume cover crops fix
atmospheric nitrogen into a form plants and
microorganisms can use. Non-legume species recycle
existing soil nitrogen and other nutrients and can
reduce leaching losses.
 Legumes Clovers, Hairy Vetch, Field Peas, Annual
Medic Forage, Alfalfa, Soybean
 Non-legumes Rye, Oats, Wheat, Oilseed Radish,
Turnips, Sudangrass, Buckwheat
 A combination of 2 or more types of cover crops may be
beneficial for quick establishment and improved
nutrient utilization.
Soil Erosion reduction
 Provide a high percentage of ground coverage as
quickly as possible
Produce more vegetative biomass than volunteer
Increase water infiltration
Decrease surface runoff
Decrease runoff velocity
Reduces soil aggregates from breaking down during
rain events
So how do these things reduce soil
 Act as a physical barrier between rainfall and the soil
surface reducing the breaking down of soil aggregates
that leads to soil erosion
 The cover reduces the rate and quantity of water
draining off fields that would cause soil erosion
 Cover crop root growth results in soil pores that allow
for higher infiltration of water
 others
Nutrient benefits of cover crops
 Cover Crops can
 Recycle farm nutrients such as N, P, K, Ca, Mg, S, etc
 Accumulate minerals at high concentrations
Buckwheat, lupine and sweet clover extract P from soils
Alfalfa can translocate nutrients from subsoil to surface root zone
 Decomposition of cover crop increases carbonic and other
organic acids through microbial activity
 Acids react with insoluble mineral rocks and release
phosphates and exchangeable nutrients
Nutrient benefits of Cover Crops
 Produces Nitrogen from legumes
 Amount is based on variety of cover crop species
 How managed (tilled in or left on top)
 Increases soil microbial activity
 Convert N to proteins and amino acids
Pesticide Use with Cover Crops
 Can increase or decrease depending on what you are
managing for
 For Weeds:
 Thick cover crop stands can prevent most germinated
weed seeds from completing life cycle and reproducing
(smother effect).
Rye residues had 80-95% early broadleaf weed control
 Can break disease cycles and reduce populations of
bacterial and fungal diseases
 Increase number of beneficial insects
 Some CC release allelochemical (natural toxins) to
inhibit or slow growth of other plants
Pesticide Use and Cover Crops
 Some CC reduce soil-borne pathogens  Rye can reduce soybean cyst-nematodes
 Some CC can be used as a trap crop for army worms,
cutworms, etc. cc must be killed 3 to 4 weeks before
 Some CC attract natural predators by providing
elements of their habitat.
 Increase organic matter that supports micro-organisms
which can break down other pesticides.
 Adds diversity to cropping system that can increase
natural controls
Soil Carbon
 Can increase carbon inputs into the soil through the
 Grasses contribute more carbon than legumes due to
higher C:N ratio
 Average C:N ratios around 10-12:1
 At ratios of 20:1 N is released
Soil Quality
 Cover Crops can:
 Increase soil microbial biomass and enzymatic activity
 Deep rooted CC can increase subsoil water holding
Bare soil holds 1.7 inches of water
Living cover crop holds 4.2 inches of soil water
 Increase soil structure and stability
 Alter soil temperatures
 Other
 Management of cover crops is key to success
 Cost of seed and application needs to be justified
 Water consumption of cover crop growth may reduce
soil moisture
May reduce soil temperature and cause slow growth in
cooler regions
Does nutrient value exceed the cost of cover crop
May harbor certain insects and disease that affect
surrounding plants and vegetation
Economic considerations of
Cover Crops
 As the cost of fertilizer and herbicides continue to
increase, the benefits of using cover crops in a
sustainable farming system will become more
attractive to modern farmers and producers.
Economic Considerations of
Cover Crops
 The economics of using cover crops can be calculated
by savings of:
 purchased nutrients
 herbicides
 versus the additional cost of using cover crops.
 There are also other factors that are not easily credited
to cover crop use, such as:
 improved soil tilth,
 enhancing soil biology,
 improving organic matter content of the soil.
Effects on Soil and Water
 Provide food for macro- and micro-organisms
 Increases evapotranspiration
 Increases water infiltration
 Decreases soil bulk density
 Reduces sediment production
 Decreases impacts of raindrops,
 Decreases runoff velocity
 Increases soil quality through biological, chemical and
physical soil properties
Effects on Soil and Water
 Increase organic carbon,
 Increases cation exchange capacity
 Increases aggregate stability
 May reduce nutrient and pesticide runoff by 50%
 May reduce soil erosion by 90%
 May reduce sediment loading by 75%
 May reduce pathogen loading by 60%
 Other
 Bob Broz
 205 Ag Engineering
 C0lumbia MO 65211
 573-882-0085
 [email protected]

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