Cover Crops Effects on Soil Health in Corn- Soybean Rotations in Iowa

Transcription

1 Cover Crops Effects on Soil Health in Corn- Soybean Rotations in Iowa Cover Crop Workshop Spring Management 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

2 Rye after Corn Silage

3 Corn and Soybeans have a 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 Benefits of Using Cover Crops Reduced erosion Reduced nitrate leaching Reduced phosphorus losses Increased soil organic matter Improved weed control Support and maintain soil organisms Improve soil structure especially no-till Grazing and forage potential Recycling manure nutrients

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

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

7 Nitrate Loss in Tile Drainage

8 Annual Flow-wt NO 3 Conc. (ppm) 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

9 Total Nitrate-N Lost in Tile Drainage Treatment Nitrate-N Lost in Drainage 14-yr total 14-yr avg. lbs/acre lbs/acre Corn-soybean no-till Corn-soybean no-till w. rye cover crop Reduction % Reduction 57

10 Cover Crops and SOM

11 Rye Cover Crop Effect on Soil Quality in a Corn Silage System after 10 years 10% more total soil organic matter (SOM) in the top 4 inches or ½% change in SOM Adding SOM improves soil structure, water holding capacity, and N mineralization (400 samples in 3.7 acres). 48% greater Potential N mineralization Rough estimates would say 8-10 lbs/acre of mineralized soil N. So this matches the OM calculations.

12 Rye Cover Crop Effect on Plant Available Water after 12 years A rye cover crop increased soil water storage capacity or plant available water in the top 12 inches by 18%, which is equivalent to an extra 0.3 inches of water every time the upper 12 inches of soil is rewetted by rainfall. The rye cover crop does use water in the spring, but in 5 out of 7 years this was replenished by the time of main crop planting. In most years after cover crop termination water contents in the upper 30 cm were higher following a rye cover crop in the summer. Basche et al. 2016

13 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.

14 AMF Propagules/100 g Soil Mycorrhizae: Propagules in soil (Brookings, SD) Soybean - Small Grains/CC - Corn Slide courtesy of Michael Lehman (USDA ARS, Brookings, SD) Slide courtesy of Michael Lehman (USDA ARS, Brookings, SD)

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16 Lumbricus terrestris middens per 0.38 m 2 on three farms in Iowa 2014/ data from Iowa Learning Farms Location Year Rye Cover Crop No Cover Crop Ames Ames Sindt Tobin Average

17 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.

18 Cereal Rye Cover Crop Root Weight and Rooting Depth in the Spring Shoot Dry Weight Root Dry Weight Rooting Depth (lbs/acre) (lbs/acre) (in)

19 Managing Cover Crops in the Spring Only winter-hardy cover crops need to killed in spring with herbicide or tillage. Oats or radish do not. Watch soil water, rainfall, and cover crop growth Before corn kill grass cover crops days prior to planting or before cover crop is 6-8 inches tall. Have a plan in place. Before soybean biggest concern is dry conditions, otherwise cover crop can be sprayed 3 days before planting. Be sure to comply with crop insurance termination dates.

20 Cover Crop Kill Date Rye Cover Crop Shoot Biomass vs Kill Date Planted Sept. 30, 2005 Shoot Biomass (Mg/ha) Mar 1 = 60 Mar 15 = 74 Mar 30 = 89 Apr 15 = 105 Apr 20 = 110 Apr. 1 Apr. 15 May DOY

21 Cover Crops & Crop Insurance in Iowa New Policies from RMA: June 2013 Termination guidelines: Zone 3 (pink): terminate at or before planting Zone 4 (blue): terminate up to 5 days after planting, but before crop emergence Corn May 31; Soybean June 15; RMA dates Cover Crops should be reported to FSA by Dec 15. NRCS cover crop termination zones for Iowa

22 Methods of Terminating Cover Crops in the Spring Herbicide Glyphosate is the most commonly used; Follow BMPs; can take a while. Tillage Usually takes two or more passes; weather dependent. Rolling or mowing can work for some cover crop species after they have flowered or headed.

23 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 Need more experiment station research on long-term benefits of cover crops and on-farm studies for improving management Need more seed, products, machinery, services, and consulting from agribusiness.