kura clover as a living mulch
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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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Soil
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Day of Year
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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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conv.Corn/soy kura corn/soyinliv.mulch
Ks,cm/hr
SaturatedHydraulicConduc vity-RosemountMNUSA
Influence of Kura Clover on Infiltration
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conv.Corn kura corninliv.mulch
Ks,cm/hr
SaturatedHydraulicConduc vity-ArlingtonWIUSA
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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Cro
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Day of Year (2011)
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
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