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

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

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

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 http://www.nass.usda.gov/Statistics_by_State/Iowa/Publications/Annual_Statistical_Bulletin/2012/index.asp

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]

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?

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’).

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)

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

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.

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

‘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)

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

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%

Cropping System Effects on Soil Physical Properties

Particulate organic matter carbon Potentially mineralizable nitrogen Soil Quality Indicators in Corn (0-20 cm; average of spring, summer, and fall 2009 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.

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.

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

Corn-Soybean-Oat/Red Clover Corn-Soybean-Oat/Alfalfa-Alfalfa Mean weed biomass in 2006-2013 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.

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.

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

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

Liebman et al., 2008

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

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

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

SDS in 2010: severe disease Rotation: p<0.0001 Variety: p<0.0001 C 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

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

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.

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

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 2006-2011: Corn: 4.35/bu; SB: 9.96/bu; Oat grain: 2.57/bu; Oat straw: 77.00/ton; Alfalfa: 117.42/ton

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

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

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

Increasing cropping system diversity balances productivity, profitability, and environmental health Davis et al. 2012. PLoS ONE

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

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