Environmental Benefits of Cover Crops

Soil Erosion, Nutrient and Pesticide Reduction Bob Broz - Extension Water Quality Specialist

205 Ag Engineering brozr@missouri.edu

Environmental Concerns Associated with Agriculture Soil erosion Nutrient runoff Pesticide runoffLoss 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 habitat.

http://www.mccc.msu.edu/

Defining Cover Crops and their Benefits to the environmentCover 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 CloverRye

Crops that are: Grown between cash crop cyclesIntercropped with cash crops to cover bare

groundPlanted 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, BuckwheatA 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 plants Increase water infiltration Decrease surface runoff Decrease runoff velocityReduces soil aggregates from breaking down

during rain events

So how do these things reduce soil erosion/sedimentAct 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 cropsCover 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 zoneDecomposition of cover crop increases carbonic

and other organic acids through microbial activityAcids 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 activityConvert 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

controlCan break disease cycles and reduce

populations of bacterial and fungal diseasesIncrease 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-nematodesSome CC can be used as a trap crop for army

worms, cutworms, etc. cc must be killed 3 to 4 weeks before planting

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 residuesGrasses contribute more carbon than

legumes due to higher C:N ratioAverage 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 capacity 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

Limitations Management of cover crops is key to successCost of seed and application needs to be

justified Water consumption of cover crop growth may

reduce soil moistureMay reduce soil temperature and cause slow

growth in cooler regionsDoes nutrient value exceed the cost of cover

crop production May harbor certain insects and disease that

affect surrounding plants and vegetationother

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 CropsThe economics of using cover crops can be

calculated by savings of:purchased nutrientsherbicides 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-organismsIncreases evapotranspirationIncreases water infiltration Decreases soil bulk density Reduces sediment productionDecreases impacts of raindrops, Decreases runoff velocityIncreases soil quality through biological,

chemical and physical soil properties

Effects on Soil and Water Increase organic carbon, Increases cation exchange capacity Increases aggregate stabilityMay 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

Questions?????Bob Broz 205 Ag Engineering C0lumbia MO 65211573-882-0085brozr@missouri.edu