Cover Crop and Living Mulch Research in Minnesota, USAJohn M. Baker

USDA-ARS, St. Paul, MN USA

Why bother with cover crops? Conventional farming practices are producing record yields

e.g. maize, soy, sorghum

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Global Per Capita Meat Consumption(kg/person/year)

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Farming has Changed

• More confined animal operations• Less grazing• Less perennial pasture• More row crop production

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Mha

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U.S. Corn Belt (MN, IA, IL, IN, OH)

• Typical maize yields 10 mt ha-1

• Typical soybean yields 3.5 mt ha-1

• Typical annual soil loss 12 mt ha-1

And we’re losing more than soil….

In the Midwest U.S.

Excess nitrogen from corn belt

Hypoxia in Gulf of Mexico

Bay of Biscay

Baltic Sea

So, our challenge is to continue increasing food production, while decreasing the environmental consequences

…..all within the context of an uncontrolled global climate experiment!

“One of the clearest trends in the U.S. observational record is an increasing frequency and intensity of heavy precipitation events”

“..it is highly likely that the recent elevated frequencies in extreme precipitation in the United States are the highest on record.”

Weather and Climate Extremes in a Changing Climate. 2008. Karl et al (eds.)

How do we do it?

• Perennialization may be the key

Brown is Bad…

Winter cover crops offer many benefits

• Erosion protection, both wind and water

• Nutrient retention & cycling

• Maintenance of soil organic matter

But, few farmers use them. Why?

Increase risk; make farming more complicated

• Establishment in fall

• Removal in spring

Timing is the problem

Often, there is little time for planting a cover

crop between harvest of the summer crop

and the onset of winter.

10 October 2013. Courtesy of Iowa State University

Aerial seeding evaluation

• Southeast MN

– Helicopter seeding

• 3 years

• 25 farms

Fall Biomass Production

Aerial seeding evaluation

• Limitations

– Aerial applicators

• Application is more

art than science

Aerially seeding winter rye

• MDA cooperator’s farms

Zumwinkle M. 2008. MDA.

Aerial Seeding Evaluation

• Limitations

– Seed Predation

With crops that are shorter than corn, there

are other seeding options

Tractor with broadcast

seeder

Tractor with

Airflow seeder

Tractor with broadcast

seeder

helicopter

Broadcast seeding produced more fall

biomass than airflow seeder or

helicopter seeding

A promising option for corn: seeding cover crop into it with a high-clearance grain drill

Red clover seeded into corn at V7

The other challenge with winter cover crops?

• When to remove them in the spring

Risk associated with removal of cover crop in spring

• If too early, no erosion protection against

spring rains

• If too late, can affect growth and yield of

following crop

Winter Rye (Cereal secale L.)

Conventional corn, Seeded 21 May Avg. Ht . = 45.8 cm Growth Stage = 4.3

Corn after Rye, Seeded 21 MayAvg. Height = 19.4 cm Growth Stage = 2.1

Western MN, June 2009

Can weather forecast models be used to decide when to terminate a cover crop?

• The Model is run every Sunday to predict

precipitation and evaporation for each day of

the week

• Those forecasts are posted on the Internet

• Useful for irrigation scheduling; or maybe for

deciding when to remove a cover crop?

Monday Precipitation Forecast

Tuesday Precipitation Forecast

Wednesday Precipitation Forecast

Thursday Precipitation Forecast

Friday Precipitation Forecast

Saturday Precipitation Forecast

Sunday Precipitation Forecast

Monday Evaporation Forecast

Tuesday Evaporation Forecast

Wednesday Evaporation Forecast

Thursday Evaporation Forecast

Friday Evaporation Forecast

Saturday Evaporation Forecast

Sunday Evaporation Forecast

For each day, the difference between

forecast precipitation and evaporation

is the forecast soil moisture change.

This could help farmer in deciding

when to remove cover crop

Of course, the uncertainty increases as

the forecast length increases

Conclusions

• Increased use of winter cover crops in northern climates depends on finding reliable ways to seed the cover crop early (before the summer crop has been harvested)

• The risk of drought stress for a crop following a winter cover may be reduced with better tools for deciding when to terminate the cover crop.

Living mulchesPerennial Legume Mulch Systems for Row Crop Production

Photosynthesis

Photosynthesis - Data from adjacent fields, Rosemount MN 2010

Annual Row crops

Perennial growing season

Kura clover

• Cold tolerant• Drought tolerant• Can fix up to 150 kg N ha-1

• Spreads by rhizomes

Kura clover

3 April

alfalfa

Maize & soybean fields (not planted yet)

Managing a living mulch

Mowing

Strip tillage

Fertilizer

Planting

Herbicide

In years with adequate rain -

Silage production nearly equivalent to conventional corn, with substantially less N fertilizer, and much better erosion protection

Soil solution NO3 at 1 m Depth

- Conventional corn

- Corn in living mulch

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What about soil protection/erosion reduction?

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1. conventional row crop (maize or soybean)

2. pure kura clover (5-7 years old)

3. living mulch (maize or soybean growing in kura clover).

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Multiple measurements of infiltration in adjacent fields

Same soil type, different cropping history

Infiltration Measurements

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Ks,cm/hr

SaturatedHydraulicConduc vity-RosemountMNUSA

Influence of Kura Clover on Infiltration

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Influence of Kura Clover on Infiltration

High infiltration rates reduce runoff

Does the clover reduce grain yield?

• Water use is the primary concern

• New experiment started under center pivot

• 4 treatments:

irrigated conventional corn/soy rotation, full tillage rainfed conventional corn/soy rotation, full tillage

irrigated corn/soy rotation in living mulch

rainfed corn/soybean rotation in living mulch

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Living Mulch-rainfed

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conv.Irr. LMirr conv.Dry LMdry

mt/haMaizeGrainYield,2013

21 %

13 %

What else might be affecting grain yield?

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2011 Maize Crop Height

Conventional maize

Maize in kura clover living mulch

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Grainmoistureatharvest,2013

A strong start is critical

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Slow early growth in living mulch is also a problem for soybean

• First year tested, yields in LM were 30% lower than conventional field

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Causes for slow start

• Cooler temperatures in seed bed

• Competition for water, nutrients, light

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Strip Tillage

Young corn in strip-tilled living mulch

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Can rotary zone tillage produce a better seedbed?

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One more factor to consider

• In living mulch system, unlike conventional corn, we can harvest both grain and stover

• The stover has economic value for feed or biofuel

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Estimated total income*

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conv.Irr. LMirr conv.Dry LMdry

Grossincome,$/ha

*On LM plots, both stover and grain are harvested.

Assumes value of corn grain = $215/mt, corn stover = $79/mt (dry weights)

Continuing Challenges

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• Kura clover grows slowly when first planted– it takes two years to develop a good stand

• Difficult to find seed – producers aren’t interested

• Can we make it work without Roundup-ready corn & soy?

Our Ultimate Goal:Farming practices that• improve soil & water quality

• increase farm income & our ability to feed people