Effect of cover crop mixture species

Cover crop mixture

diversity, biomass

production and

weed suppression

Angela TranUniversity of Nebraska-Lincoln

OutlineThe motivationThe question

The methodologyThe outcome

THE MOTIVATIONWhy study diverse cover crop mixtures?

Photo by Tom Stromme of The Bismarck Tribune.

Increasing interest in the use of diverse cover crop mixtures.

Cover crop research mainly on monocultures.

Photo from Practical Farmers of Iowa.

Cover crop mixture research mainly on bi-cultures.

Photo from The Ohio State University Extension.

Little research on diverse, multi-species cover crop mixtures.

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No.

pos

sible

com

bina

tions

No. species

Possible combinations of nspecies.

Missing fundamental information about cover crop mixtures.

How are mixtures different from monocultures?

Why?

How do I design my cover crop mixture?

THE QUESTIONWhat is it that we want to know?

What is the effect of diversity

on performance?

Diversity

Perfo

rman

ce

Diversity

Perfo

rman

ce

?

Diversity

Perfo

rman

ce

?

Diversity

Perfo

rman

ce

?

Defining performance• Biomass production• Weed suppression

Diversity

Perfo

rman

ce

Defining diversity• No. species

• No. functional groups

Diversity

Perfo

rman

ce

Species

Functional groups

THE METHODOLOGYHow did we approach answering our research question?

No. Species Species Functional Groups

1 No Cover 0 02 Barley (Spring) 1 13 Oats (Spring) 1 14 Wheat (Spring) 1 15 Austrian Winter Pea 1 16 Mammoth Red Clover 1 17 Yellow Blossom Sweetclover 1 18 Radish 1 19 Rapeseed 1 1

10 Turnip 1 1


1 No Cover 0 02 Barley (Spring) 1 13 Oats (Spring) 1 14 Wheat (Spring) 1 15 Austrian Winter Pea 1 16 Mammoth Red Clover 1 17 Yellow Blossom Sweetclover 1 18 Radish 1 19 Rapeseed 1 1

10 Turnip 1 1

Cover crop treatments (#1-10)No. Species Species Functional

Groups1 No Cover 0 02 Barley 1 13 Oats 1 14 Wheat* 1 15 Austrian Winter Pea 1 16 Mammoth Red Clover 1 17 Yellow Blossom Sweetclover 1 18 Radish 1 19 Rapeseed 1 1

10 Turnip 1 1


1 No Cover 0 02 Barley 1 13 Oats 1 14 Wheat* 1 15 Austrian Winter Pea 1 16 Mammoth Red Clover 1 17 Yellow Blossom Sweetclover 1 18 Radish 1 19 Rapeseed 1 1

10 Turnip 1 1


1 No Cover 0 02 Barley 1 13 Oats 1 14 Wheat* 1 15 Austrian Winter Pea 1 16 Mammoth Red Clover 1 17 Yellow Blossom Sweetclover 1 18 Radish 1 19 Rapeseed 1 110 Turnip 1 1

*spring variety


11 Grass Mix (Barley, Oats, Wheat) 3 112 Legume Mix (Peas, Red Clover, Sweetclover) 3 113 Brassica Mix (Radish, Rapeseed, Turnip) 3 114 Grass Mix + Legume Mix 6 215 Grass Mix + Brassica Mix 6 216 Legume Mix + Brassica Mix 6 217 Grass Mix + Legume Mix + Brassica Mix 9 318 Barley, Peas, Radish 3 319 Oats, Red Clover, Rapeseed 3 320 Wheat, Sweetclover, Turnip 3 3

Cover crop treatments (#11-20)No. Species Species Functional

Groups11 Grass Mix (Barley, Oats, Wheat) 3 112 Legume Mix (Peas, Red Clover, Sweetclover) 3 113 Brassica Mix (Radish, Rapeseed, Turnip) 3 114 Grass Mix + Legume Mix 6 215 Grass Mix + Brassica Mix 6 216 Legume Mix + Brassica Mix 6 217 Grass Mix + Legume Mix + Brassica Mix 9 318 Barley, Peas, Radish 3 319 Oats, Red Clover, Rapeseed 3 320 Wheat, Sweetclover, Turnip 3 3







Cover crops broadcasted…

After small grains harvest (3)

Into maturing soybeans (3)

Into maturing corn (2) or after seed corn

harvest (1)

Across nine fields at six farms.

Sampling and measurements

Species specific cover crop and weed biomass sampled before fall frosts . Plant tissue dried to a constant weight at 65°F.

Cover crop and weed biomass sampled before fall frosts.

THE OUTCOMEWhat have we found so far?

Cover crop establishment highly variable across sites.

Only one site with substantialcover crop growth.

Hooper, NE (harvested wheat field)Cover crops seeded 8/31/13.

Plant biomass sampled 10/31/13.

Biomass productionData has many possible narratives.

An ecological narrative• Pre-existing framework

• ↑ diversity, ↑ productivity

An agronomic narrative• More relevant to agricultural management?

• < diverse systems can be just as productive as > diverse systems

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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20

Barley Oats WheatPea Red Clover SweetcloverRadish Rapeseed Turnip

Error bars (±SEM).

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ass (lb/A)

Treatment No.

An ecological narrative

Tilman, D. 2001. Functional Diversity. p. 109-120 in S. A. Levin (ed.) Encyclopedia of biodiversity. Academic Press: San Diego, CA.

Tilman, D., J. Knops, D. Wedin, P. Reich, M. Ritchie, E. Siemann. 1997. The Influence of Functional Diversity and Composition on Ecosystem Processes. Science 277: 1300-1302.

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No. functional groupsNo. species

Data fit to rectangular hyperbola (Y = I*X/[1+(I/A)*X]). Error bars (±SEM).

An agronomic narrative

Less concerned with averages.

More concerned with instances.

Are there instances where less diverse systems produce more than

more diverse systems?

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No. functional groupsNo. species

Species diversity confounded with functional diversity.

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Grasses Legumes Brassicas

1 species 3 species

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Functional group

Error bars (±SEM); p-value <0.10.

NS

NS

NS

Monocultures and 3-way mixes within the same functional

group performed the same.

On average.

Not in every instance.


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Functional groupGrasses Legumes Brassicas

A

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BB B

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500Barley Oats WheatPea Red Clover SweetcloverRadish Rapeseed Turnip

With regard to species diversity alone, monocultures can

outperform mixtures.

What about with regard to functional diversity?

B

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No. species = 3; p-value <0.01.

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No. functional groups

Increasing functional diversity increased biomass production.

On average.

Not in every instance.

1 3


-------------------NS-------------------

No. species = 3; p-value <0.01.

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500Barley Oats WheatPea Red Clover SweetcloverRadish Rapeseed Turnip

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ass (lb/A)

Biomass production

Possible narratives

Ecological—↑ diversity, ↑ productivityThe narrative of averages

Agronomic— < diverse systems can be just as productive as > diverse systems

The narrative of instances

Weed SuppressionData range limitations prevented

evaluation of the relationship between mixture diversity and weed suppression

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Wee

d b

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ass

(g/m

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Cover crop biomass (g/m2)

No cover

Legume only covers

All other covers

Looking ForwardBeyond biomassNutrient cycling

Faunal biodiversity

Adding functional groupsWarm season grasses, legumes,

broadleaves

QUESTIONS/COMMENTS

Cover crop mixture diversity, biomass production and weed suppression

EXTRA SLIDES

Cover crop mixture diversity, biomass production and weed suppression

Biomass production

On the mechanisms behind diversity-productivity relationship

Suggested mechanisms include the idea that one species enhances the success of another.

For this project, however, mechanism may be a simple artifact of the relationship between

seeding rate and biomass.

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Seeding rate

Radish as an exampleRecommended broadcast rate*: 8-14 lb/A

Selected rate for this project: 15 lb/AWith ≈ 25,000 seeds/lb, that is seeding ≈ 9 seeds/ft2.

*Clark, A. (ed.) 2007. Managing cover crops profitably. 3rd ed. SARE Program, College Park, MD.

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Barley Pea Radish

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Treatment No.

Could more diverse systems be more economical ways to get more biomass?

Seeding datesLocation Field Type Seeding Date

Keene, NE Wheat stubble 7/19/13

Marquette, NE Barley stubble 8/10/13

Hooper, NE Wheat stubble (disked) 8/31/13

Mead, NE Soybean (R5) 9/10/13

Hooper, NE Soybean (R7) 9/12/13

Marquette, NE Soybean (R6) 9/14/13

Hooper, NE Corn 9/12/13

Waterloo, NE Corn stubble (disked) 9/19/13

Bladen, NE Corn 9/20/13

Seeding ratesSpecies

Full broadcast rate (lb/A)

Suggested * Selected

Barley 80-125 150

Oats 110-140 150

Wheat 60-150 150

Austrian winter pea 90-100 100

Red clover 10-12 15

Yellow blossom sweetclover 10-20 15

Radish 10-20 15

Rapeseed 8-14 15

Turnip 10-12** 15*Clark, A. (ed.) 2007. Managing cover crops profitably. 3rd ed. SARE Program, College Park, MD.

**Björkman, T. 2009. Forage Turnips and Rape. Available at http://www.hort.cornell.edu/bjorkman/lab/covercrops/turnip.php (verified 3 Mar . 2013). Cornell University, Cornell, NY.

Liz Morrison, Corn and Soybean Digest (Jan. 1, 2011).

John Dietz, Hay & Forage Grower (Aug. 1, 2008).

Graze (May 1, 2013).

Cover Crop Cocktail Research Team, Penn State College of Agricultural Sciences (2013).This image cannot currently be displayed.

Andrew McGuire, Washington State University (April 17, 2013).

This image cannot currently be displayed.


John Michaelson, Tennessee News Service (Jan. 20, 2014).

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Error bars (±SEM); p-value <0.01 All three species included for addition of each functional group.

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Treatment No.

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Soil Nitrate (ppm)

No Cover9-Way Cocktail

p-value < 0.10 (*), <0.01 (**)

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No CoverGrass MixLegume MixBrassica Mix9-Way Cocktail

p-value < 0.10 (*), <0.01 (**)

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p-value < 0.10 (*), <0.01 (**)

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p-value < 0.10 (*)

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p-value < 0.10 (*), <0.01 (**)

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It makes little sense if you know what you are doing.

Diversification is protection against ignorance.

Photo by Ben Baker of Redux.

Environment

Effect of cover crop mixture species