SOUTHERN AGRICULTURAL COVER CROPS WORKSHOP Jonesboro, AR July 24-25, 2013

Transcription

1 Things to Consider when Establishing Cover Crops SOUTHERN AGRICULTURAL COVER CROPS WORKSHOP Jonesboro, AR July 24-25, 2013 Kip Balkcom Research Agronomist USDA-ARS National Soil Dynamics Laboratory Auburn, AL

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3 High Erosion Potential

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5 Conventional Tillage Promotes SOM Oxidation

6 Soil C is the basis of Soil Quality/Productivity NH and NO, 4 3 P, K, Ca, Al, CEC Microbial Biomass C and N N Soil Respiration Biomass C to TOC ratio mineralized Respiration to Biomass ratio Total Organic C and N C capacity retention content Water Aggregate Stability Size Distribution Bulk Density Soil Strength Infiltration from Doran et al., 1993

7 Residues/Soil C Surface soil effects are most critical

8 How to improve soil quality Build soil C near the soil surface Minimize surface soil tillage No tillage/non inversion tillage Continuous residue/cover crops Cover crops are key Crop rotations Break pests/disease cycles

9 Manage compaction...

10 Non-inversion Tillage

11 Effect of cropping/tillage system on soil C from an eroded Ultisol in Georgia. Grain sorghum no-till into crimson clover mm mm mm conversion to conventional till soybean Year Bruce et al., 1995

12 How to improve soil quality Build soil C near the soil surface Minimize soil tillage No tillage/non inversion tillage Continuous residue/cover crops Cover crops are key Crop rotations Break pests/disease cycles

13 Why use Cover Crops? Erosion control Soil and water quality improvement Increased water infiltration Minimize nutrient loss Soil organic carbon

14 What is a Cover Crop? A crop whose main purpose is to benefit the soil and/or a subsequent crop in one or more ways, but is not intended to be harvested for feed or sale. Courtesy: Harry Schomberg, USDA-ARS

15 High Residue Cover Crop

16 Cover Crop Fertilization

17 Alternative N Sources

18 Rye biomass, lb ac No N 30 lb ac lb ac 90 lb ac 1.0 ton ac ton ac ton ac -1 Cover crop N rate

19 Biomass Production Time of Termination Biomass, lb ac Rye before Corn Wheat before Corn Rye before Cotton Wheat before Cotton

20 Timing Termination 2-4 weeks MAY 1

21 Soil Water Conservation Plot 141 Plot 142

22 Conservation Systems Absorbs rainfall impact Cooler soil temps Lower evaporative losses Greater soil water infiltration Increases plant available water

23 Rainfall Simulation Study...

24 Rainfall simulation 2 inch rain event 100 Rainfall infiltration, simulate 2-inch rain days Rainfall, % days 20 0 Strip w/residue Strip no residue Conventional tillage

25 Increased Plant Available Water Increases efficiency of a rain or irrigation event. Potential lower water requirements. Preserve water resources and lower production costs. $ $

26 How to increase soil C and improve soil quality? Conservation Tillage with Cover Crops Conservation System

27 How to improve soil quality Build soil C near the soil surface Minimize soil tillage No tillage/non inversion tillage Continuous residue/cover crops Cover crops are key Crop rotations Break pests/disease cycles

28 The Old Rotation (circa 1896) Auburn, Alabama

29 Old Rotation yield increase from first ten years ( ) Yield Increase (%) Cot Cot(Leg) Cot/Corn (Leg+ N) Cot/Corn/Wht- Soy (Leg+ N)

30 Ripper Modification

31 Planter Attachments

32 Planter Attachments Cotton seeds

33 Drill Modification Spoke closing wheels

34 Summary Plant covers in a timely fashion. Consider additional N fertilizer for small grain cover crops, especially if residual N is low. Terminate covers ~ 3 weeks ahead of anticipated planting date to allow soil moisture recharge and reduce problems with equipment operation. Take advantage of equipment modifications to facilitate tillage and/or planter operations in heavy residue.

35 Conservation Systems Research More information available at: Subscribe to mailing list:

36 Grower Adaptation

37 One pass vs. Multiple pass