Institute of Ag Professionals

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1 Institute of Ag Professionals Proceedings of the 2014 Crop Pest Management Shortcourse & Minnesota Crop Production Retailers Association Trade Show Do not reproduce or redistribute without the written consent of author(s).

2 Research on Winter Rye Cover Crops in Corn- Soybean Rotations in Iowa 2014 CPM Short Course and MCPR Trade Show Minneapolis, MN USDA-ARS National Laboratory for Agriculture and the Environment Ames, Iowa Tom Kaspar Ben Knutson Keith Kohler Kent Heikens Dan Jaynes Tim Parkin Tom Moorman Britt Moore Lara Schenck

3 Corn and Soybeans have a 5 to 7 Month BROWN Gap Corn or Soybean Crop at Maturity approx. Oct. 1 Phosphorus Soil productivity is lost during the BROWN gap because there are no GREEN plants to protect soil and recycle nutrients. Soil OM Topsoil Nitrogen Corn or Soybean Crop at Emergence approx. May 1 Winter Cover Crops Catch Losses Cover Crops Fill the BROWN Gap with GREEN Plants

4 Principles of Cover Crops Continuous living cover at least when the ground is not frozen more like natural systems adds plant diversity Recycling nutrients all of them Continuous inputs of carbon Soil C is an inputs and outputs game Continuous water use transpiration versus evaporation/leaching Competition with weeds Support and maintain soil organisms Soil surface protection and insulation Cover crops are a long-term investment

5 Why Focus on Cover Crops for Corn-Soybean Rotations Illinois 95% of harvested cropland Indiana 92% Iowa 94% Minnesota 77% Ohio 81% Because most of the harvested cropland in 2012 was in these two crops in the Upper Midwest.

6 How Many Acres of Corn and Soybean have Cover Crops Now and How Many Acres Could have Cover Crops In Iowa the 2012 NASS Census of Agriculture reported 379,614 acres of cover crops in Iowa = 1.6% harvested cropland Kladivko et al 2014 estimated that cover crops could be planted on 70 to 80% of the agricultural land in two Iowa counties We have a long way to go! Especially since cover crops are a big part of Iowa s voluntary Nutrient Reduction Plan

7 Corn and Soybeans in Iowa and Minnesota Leave a Relatively Cold and Short Growing Season for Cover Crops Average Date of Planting and Harvest Progress NASS Corn Iowa Minnesota 20 % Planting Completed 22-Apr 23-Apr Soybean 80% Harvest Completed 10-Nov 9-Nov 20 % Planting Completed 8-May 9-May 80% Harvest Completed 19-Oct 18-Oct

8 Shoot Dry Weight (Mg/ha) Rye Winter Cover Crop Spring Shoot Dry wt vs Fall GDD with a 4ºC Base y = -8E-06x x R² = Fall GDD

9 Growing Degree Days 0 C base GDD 4ºC Remaining vs DOY at Ames - Story Co. Aug 1 = DOY 213 = 1221 GDD Sept 1 = DOY 244 = 660 GDD Oct 1 = DOY 274 = 237 GDD Nov 1 = DOY 305 = 15 GDD 50% 28ºF = DOY 287 (Oct 14) = 118 GDD Sept 1 Oct. 1 Frost Date Nov DOY

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11 Cover Crop Shoot Dry Weight (Mg/ha) Cultivar Species 4-yr. Avg. 4-yr Rank Elbon rye 2.16 a 1 Aroostook rye 2.13 a 2 Maton rye 2.11 a 3 Dacold rye 1.83 b 4 Rymin rye 1.73 bc 5 Oklon rye 1.69 bcd 6 Wheeler rye 1.66 bcd 7 Pronghorn winter wheat 1.57 bcd 8 Nekota winter wheat 1.49 cd 9 Wesley winter wheat 1.46 d 10 NE-422t triticale 1.15 e 11 Boreal triticale 0.94 e 12 Avg LSD (0.10) 0.27

12 What Do We Know About Cover Crops Mixtures for Corn Soybean Rotations in Iowa? Not Much! Or at least I don t know much.

13 Advantages of Cover Crop Mixtures More plant diversity - more like natural systems Balanced C/N ratio Different plant architecture - roots/shoots Better Pest Management Better support for soil organisms Better responsiveness to soil and weather variability Potential for more growth stability

14 Disadvantages of Cover Crop Mixtures Can be more expensive Can be difficult to seed/plant Termination may be more complicated Residual herbicides can more of a problem We don t know much

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16 Steve Berger Erosion and Cover Crops

17 Steve Berger

18 Which side has 30% cover?

19 Erosion Measurements with Simulated Rainfall NO COVER CROP OAT COVER RYE COVER

20 Relative Erosion Rate (% ) Relative Erosion Relative Rill and Interrill Erosion Rate in No-till Soybean as Affected by Cover Crops No Cover Crop Oat Rye Interrill Erosion Rill Erosion Kaspar et al., 2001, J. Soil Water Conserv.

21 RUSLE2 Erosion Estimates Using Beta Version of Cover Crop Vegetation Files Corn Soybean rotation, NT, spring anhydrous, 5% slope, 150 ft slope length, Ames, IA - without rye cover crop = 2.1 t/ac/yr - with rye cover crop = 1.2 t/ac/yr Continuous Corn Silage, NT, spring anhydrous, 5% slope, 150 ft slope length, Ames, IA - without rye cover crop = 4.8 t/ac/yr - with rye cover crop = 1.9 t/ac/yr

22 Why do Cover Crops Reduce Erosion in No-till Increased surface residue cover and infiltration only a little bit Cover crops anchored surface residue and prevented it from moving Added some height and layers to surface residue cover Slowed water movement across the surface Roots in near surface soil seemed to help prevent detachment More intensive rainfall events

23 Nitrate Loss in Tile Drainage

24 Flow Meters & Sample Collectors Kaspar et al. J. Environ. Qual. 36:

25 Tile flow (mm) Rain (mm) Cumulative Annual Drainage No Cover Crop Rye Cover Crop Avg 0

26 Annual Flow-wt NO 3 Conc. (mg-n L -1 ) Nitrate-N Concentration 30 Annual Flow-wt NO3 Concentration of Tile Drainage for Corn- Soybean Rotation near Ames, IA with or without a Cover Crop No Cover Crop Rye Cover Crop Avg Year

27 Nitrate (mg-n L -1 ) Drainage Water Nitrate Concentration Flow Weighted N Concentration 2 Low N = 10.6 mg N/L No Cover Crop = 13.2 Winter Rye Cover Crop = Mar 21-Apr 10-Jun 30-Jul 18-Sep

28 Total Nitrate-N Lost in Tile Drainage Treatment Nitrate-N lost 12-yr total 12-yr avg lbs/acre lbs/acre Corn-soybean Corn-Soyb w. Rye Reduction % Reduction 55

29 Cover Crop Cover Crop Cover Crop Cover Crop Reduction Shoot Shoot N Shoot N of Drainage Biomass Concentration Content N Loss lbs/acre % lbs N/acre lbs N/acre Avg Sum

30 Reduction of Nitrate Leaching with Rye Four Other Iowa Sites Nashua, Iowa 22 29% Gilmore City, Iowa 15-20% COBS Experiment, Kelly, Iowa 36% Tim Smith farm, Eagle Grove, Iowa 48% Data from Matt Helmers, Eileen Bader, Tim Smith, and A.L. Daigh

31 Slide from Eileen Bader with The Nature Conservancy

32 Why Does Cover Crops Effectiveness Vary from Site-to Site? Would expect it to vary Different amounts of cover crop growth Different weather at the sites Different soil types OM, texture Tile spacing, tile depth, effectiveness Different crop management Different field history

33 Cover Crops and SOM

34 Rye Cover Crop Effect on Soil Quality in a Corn Silage System after 10 years A rye cover crop increased total soil organic matter (SOM) in the top 4 inches from 4.8% to 5.3% or ½% change in SOM Very rough estimates would say a ½% change in SOM would result in an additional ½ inch of water and 11 kg/ha of mineralized soil N. 48% greater Potential N mineralization Rough estimates would say this would be 9-11 kg/ha of mineralized soil N. These are really hard measurements to make

35 Soil biology/earthworms Plant growth during normally fallow period (Sept-Nov, March-April) provides continuous and stable food source for soil organisms Plant cover moderates temperature and water content. Diversity of plant materials may also increase diversity of soil biological community Soil organic matter maintained and cycled from coarse residue to humic acids. Eileen Kladivko Purdue Univ.

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37 Lumbricus terrestris middens per 0.38 m 2 on three farms in Iowa data from Iowa Learning Farms Location Rye Cover Crop No Cover Crop Ames Sindt Tobin Average 9.73 A 7.13 B

38 Roots are important When building soil quality, esp. with NT, the cover crop ROOTS are probably more significant than the shoot growth Still need good shoot growth for erosion control, mulch effects for moisture conservation, weed suppression, etc. Eileen Kladivko Purdue Univ.

39 Steve Berger

40 Cereal Rye Cover Crop Root Weight and Rooting Depth in the Spring Year Root Dry Weight Shoot Dry Weight Rooting Depth (kg/ha) (kg/ha) (cm) Avg

41 From realfarmer.ca

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43 Future of Cover Crops Great untapped potential Cover crop cultivars/species that are better adapted, grow faster, winter hardy, and easy to terminate. Need public breeding programs Cover crop mixtures could be even better More experiment station research on longterm benefits of cover crops and on-farm studies for improving management More seed, products, machinery, services, and consulting from agribusiness.

44 Midwest Cover Crops Council Website

45 Questions? ars.usda.gov