1. Diversification With Perennials:
How Does it Affect Cropping System Performance?
Matt Liebman
Iowa State University . 1

2. A massive loss of perennial cover in Iowa farmland• • •

3. SIMPLIFICATION and HOMOGENEITY of LANDSCAPES
Corn and soybean in Iowa: 63% of total land area, 82% of cropland
Wright County, 2011
583 sq. miles
(1,509 sq. km.)
Yellow = corn
Green = soybean
USDA-NASS Cropland Data Layer

4. Iowa, 2011: A remarkable record of production
2.4 billion bushels of corn harvested
466 million bushels of soybean harvested
2.4 million cattle, 38.7 million hogs, and 14.4 billion eggs marketed
$30.5 billion of farm income from crops and livestock

5. Environmental impacts of simple, conventional cropping systems
Substantial nutrient emissions to water. Nitrogen concentrations in drainage and surface waters are proportional to fertilizer rates and the amount of land used for row crops (Schilling & Libra, 2000; Randall, 2006).
Frequent detection of herbicides in surface water. Concentrations are proportional to the amounts applied in surrounding areas (Sullivan et al., 2009).
Herbicide resistance in weeds. More species are evolving resistance and stacked resistances to multiple modes of action are apparent (Beckie, 2006; Heap, 2012).
Continuing problems with soil erosion. Erosion problems will likely be exacerbated by a greater frequency of high intensity storms (Angel et al., 2005; EWG, 2011; Heathcote et al., 2012).
Randall, 2006 [Corn N Management]

6. Can diversifying corn and soybean systems with small grain and forage crops :
reduce requirements for purchased inputs?
maintain or improve productivity, profitability, and weed suppression?
reduce susceptibility to certain diseases?
improve environmental performance characteristics?

7. The Marsden Farm cropping systems experiment was initiated in 2001 in Boone Co., IA. There are 36 plots, each 18 m x 84 m (60’ x 275’).

8. Three rotation systems in four replicate blocks, with each phase of each rotation present each year. June 2012 view. S3 S4 C2 A4 C3 O3 C4 O4 S2 S4 C4 S3 C2 O3 C3 S2 O4 A4 S4 A4 O3 C2 S2 C3 O4 S3 C4 C4 O3 S4 C2 S2 O4 C3 S3 A4
2-year rotation: corn-soybean (cash grain)
3-year rotation: corn-soybean-oat/red clover (green manure)
4-year rotation: corn-soybean-oat/alfalfa-alfalfa (hay)

9. Changes in crop location in different rotation systems over time
2-year rotation
3-year rotation
4-year rotation
Year 1
Year 2

10. Integration of crop and livestock systems:
composted beef manure applied to red
clover and alfalfa, before corn, in the 3-year
and 4-year rotations.

11. Nitrogen Fertility Management in Contrasting Rotation Systems
Corn
2-year
100 lb N/acre applied at planting with additional N side-dressed according to test results
3-year and
4-year
(Legume residues + manure)
No fertilizer N applied at planting
N side-dressed according to test results

12. ‘Technology packages’ used for corn and soybean
Rotation
Corn
Soybean
2-year
Agrigold 6395 Yield Guard Plus (transgenic)
Broadcast herbicides:
Dual II Magnum (S-metolachlor) and Balance Pro (isoxaflutole), or Zidua (pyroxasulfone) and Balance Pro
Kruger 287RR (transgenic)
Broadcast herbicide:
Glystar Plus, Roundup PowerMax, or Cornerstone Plus (glyphosate)
3-year and
4-year
Agrigold 6395 (non-transgenic)
Banded herbicides:
Callisto (mesotrione) and Steadfast (nicosulfuron + rimsulfuron) or Laudis (tembotrione)
Kruger 2918 (non-transgenic)
Select (clethodim), Cobra (lactofen) and Resource (flumiclorac pentyl ester), or Select and Cadet (fluthiacet-methyl)

13. Asynchronous harvests
Reducing herbicide use with multiple tactics in diversified cropping systems
Cultivation
Asynchronous harvests
Stubble clipping &
hay removal
Banded
herbicides

14. Mean annual synthetic N fertilizer and herbicide use, 2006-2013
Herbicides
Rotation
2-year
3-year
4-year
kg N/ha
kg a.i./ha
Corn
164 24 21
1.76
0.07
Soybean 2
1.67
0.14
Oat --
Alfalfa
Rotation av. 83 10 7
1.71
0.05
Reduction
-88%
-91%
-96%
-97%

15. Cropping System Effects on Soil Physical Properties

16. Particulate organic matter carbon Potentially mineralizable nitrogen
Soil Quality Indicators in Corn (0-20 cm; average of spring, summer, and fall and spring 2010 sampling dates)
Rotation
Particulate organic matter carbon
Potentially mineralizable nitrogen
mg POM-C cm-3 soil
mg PMN cm-3 soil
2-year
1.86 b
30.8 b
3-year
2.44 a
42.1 a
4-year
2.38 a
38.3 a
Soil managed with longer rotations has more POM-C and PMN.
Source: P. Lazicki & M. Wander, unpublished data
Note: Measurements made in Agrigold 6395BtRW-PRE sub-plots in all rotations.

17. Estimated Soil Erosion (RUSLE2)
Tons per acre per year
2-year rotation: 1.36
3-year rotation: 1.08
4-year rotation: 0.88
3-yr reduced 20.5% and 4-yr reduced 35.3% relative to 2-yr.

18. Weeds: three assessment approaches
Weed biomass in “bulk areas”
Weed seed densities in “bulk areas”
Weed seed densities in manipulated (“pulse-chase”) subplots

19. Corn-Soybean-Oat/Red Clover Corn-Soybean-Oat/Alfalfa-Alfalfa
Mean weed biomass in was low in the corn and soybean phases of each system. Weed growth was greater in oat and alfalfa phases.
Crop phase
2-year:
Corn-Soybean
3-year:
Corn-Soybean-Oat/Red Clover
4-year:
Corn-Soybean-Oat/Alfalfa-Alfalfa
lb/acre
Corn 2 4
Soybean
1 b
4 ab
2 b
Oat/legume
---
62 a
23 b
Alfalfa 44
Backtransformed means (ln x+1) presented. Analysis run on ln x+1 transformed data.
Within crops, means followed by different letters are significantly different.

20. Seedbank sampling Seedbank sampling was conducted each year in april
-Click-
Seeds were separated from soil using an elutriator
The number of viable seeds present each spring was determined using germination and tetrazolium tests.

21. Weed seed density in soil has declined in all systems.
Davis et al., 2012

22. Assessing weed demography: a pulse-chase approach
Background seed bank densities
determined in 2002
Weed seeds applied in Nov. 2002:
2000 giant foxtail m-2 +
500 velvetleaf m-2
Resulting seed and plant densities
measured for four years
84 m 7m
Velvetleaf
Giant foxtail 7m
18 m

23. Liebman et al., 2008

24. By 2006, herbicide-related aquatic ecotoxicity was
two orders of magnitude lower in the more diverse rotations.
Davis et al., 2012

25. Sudden Death Syndrome
Caused by a soilborne fungus - Fusarium virguliforme
Root infection causes root rot and poor root vigor
Leaf symptoms caused by fungal toxins moved from roots to leaves
Disease favored by cool, wet weather
Yield losses can be severe

26. Rotation plots in the 2010 SDS Epidemic
3-year rotation
2-year rotation
Photo courtesy of L. Miller

27. SDS in 2010: severe disease Rotation: p<0.0001 Variety: p<0.0001C B
Rotation: p<0.0001
Variety: p<0.0001
Interaction: p<0.0001 A B
Rotation: p=0.0001
Variety: p<0.0001
Interaction: p=0.1837 C C D D

28. SDS in 2011-2013: low disease Rotation: p=0.0005 Variety: p=0.0017
Interaction: p=0.0452 B B B B B A
Rotation: p=0.0001
Variety: p<0.0001
Interaction: p=0.0440 B B B B B

29. Yields, 2006-2013 Crop Corn (bu/acre) 186 b 192 a 195 a
2-year rotation
3-year rotation
4-year rotation
Corn (bu/acre)
186 b
192 a
195 a
Soybean (bu/acre)
47 c
51 b
54 a
Oat (bu/acre)
---
93 b
97 a
Alfalfa, 2nd year (tons/acre)
4.2
2-yr vs 4-yr: Corn +5%; Soybean +15%; 3-yr vs 4-yr: Oat +4%
Sources: Liebman et al., 2008; Cruse et al., 2010; Gómez et al., 2012; Davis et al., 2012.

30. Economic performance and fossil energy use
were assessed on a land area basis.
2-year rotation
3-year rotation
4-year rotation
600 acres
300 acres corn
300 acres soybean
600 acres
200 acres corn
200 acres soybean
200 acres oat
600 acres
150 acres corn
150 acres soybean
150 acres oat
150 acres alfalfa

31. Cost and Price Assumptions
Input costs were taken from ISU Extension and Outreach’s annual report “Costs of Crop Production in Iowa,” and from local businesses. Machinery operation costs and labor were based on field notes and ISU E&O’s “Estimating field capacity of farm machines.”
Manure was assumed to be generated by on-farm or local livestock and therefore without cost for the material, but with labor and machinery costs for spreading.
Grain and hay prices were taken from marketing year average crop prices as reported annually by the Iowa office of the USDA National Agricultural Statistics Services. Subsidy payments were not included.
Prices used for :
Corn: 4.35/bu; SB: 9.96/bu; Oat grain: 2.57/bu; Oat straw: 77.00/ton; Alfalfa: /ton

32. Gross returns, costs, and profits, 2006-2011
Rotation
2-year
3-year
4-year
Gross returns ($/acre)
673 a
585 b
588 b
Costs of production, including labor ($/acre)
287 a
193 b
219 b
Profits (returns to land and management, $/acre)
386 a
392 a
369 a
Diversitylower gross returns, lower costs, similar profits
Johanns et al., 2012

33. Energy, labor, and profits, 2006-2011
Rotation
2-year
3-year
4-year
Fossil energy inputs (barrels of oil equivalent/acre)
0.61 a
0.24 b
0.26 b
p<0.0001
Labor inputs (hr/acre)
0.7 c
1.1 b
1.5 a
Profits (returns to land and management, $/acre)
386 a
392 a
369 a
p=0.59
Diversityless energy, more labor, similar profits
Davis et al., 2012

34. Assessing Cropping Systems with Multiple Performance Criteria
Davis et al., 2012

35. Increasing cropping system diversity balances productivity, profitability, and environmental health
Davis et al PLoS ONE

36. Learning, discovery, and outreach
(a famous) farmer
a researcher
a student

37. Special thanks to: C. Chase A. Davis R. Gómez A. Heggenstaller J. Hill
D. James
A. Johanns
L. Leandro
F. Menalled
D. Sundberg
P. Westerman
C. Williams