Soil Health Impacts of Cover Crops Bob Kremer & Kristen Veum USDA-ARS & University of Missouri

Transcription

1 Soil Health Impacts of Cover Crops Bob Kremer & Kristen Veum USDA-ARS & University of Missouri Cover crop screening trials - Bradford Farm

2 Acknowledgments University of Missouri Soil Health Lab Dr. David Hammer Dr. Russ Dresbach Donna Brandt University of Missouri Bradford Research & Extension Center Tim Reinbott Kerry Clark Missouri USDA-NRCS Soil Health Team USDA-NRCS Chariton County MO Field Office University of Missouri Soil & Plant Test Lab University of Missouri Agroforestry Center MMI Laboratories, Athens, GA Ward Laboratories, Kearney, NE Dr. Keith Goyne, SEAS Dr. Randy Miles, SEAS Dr. Ann Kennedy, USDA-ARS, Pullman, WA

3 Cover Crops X Soil Health Spring oats + berseem clover mixture Biodiversity in a hypothetical block of field soil -- Source: Reganold et al

4 Important biological attributes of healthy soils are influenced by vigorously growing plants Soil Microbial Diversity (Biodiversity) Soil Carbon Content & Quality -- Plant root contributions (SOM 58% C) Crimson clover provides Carbon and Nitrogen to soils Rhizobacteria on plant root surface metabolize plant-derived C and interact with plant.

5 Soil Microbial Diversity (Soil Biodiversity) [biodiversity = most valuable property of any ecosystem; E.O Wilson, 1999] Biodiversity Provides numerous pathways for primary production and ecological processes (i.e., nutrient cycling) Many processes require multiple organisms ( Consortia ) for completion Alternative pathways available if one is disturbed Ecosystem stability and resistance to stress Microbial biomass may withstand stress; diversity may be reduced Example of Structural Diversity: Bacteria Nematode Algae Fungi

6 Soil Microbial Structure and Biological Functions ( Functional Diversity ) Influenced by Plant Roots Rhizodeposition % photosynthate released into rhizosphere (depending on plant) Berg & Smalla, 2009

7 Extensive root systems of some native prairie plants Source: Conservation Research Institute

8 Ideal functional diversity in healthy soil provided the diverse microbes necessary for efficient nutrient cycling Note: Example for only one of the numerous functions microbes mediate in soils

9 Cover Crops & Maintenance of Soil Organic Matter - organic matter in the soil may be considered our most important national resource - Albrecht, Living Cover Crops Actively growing roots deliver C and nutrients to rhizosphere microorganisms *Greater retention of root C increases C sequestration compared with cash crop residue incorporation (Puget & Drinkwater 2001) Microbial functions enhanced: nutrient transformations; decomposition; plant growth regulator synthesis; aggregate formation; degrade/inactivate synthetic chemicals Active rhizobia & mycorrhizae symbiosis; associative N fixation Cover Crop Residues Organic matter inputs, building microbial biomass Provide mineralizable nutrients; active decomposition Increased microbial diversity; potential pathogen & weed suppression Improved soil aggregate stability Increased number, diversity, activity of soil micro-, macro fauna

10 SOM Crop residue Components Bacteria Fungi Actinobacteria SOM CO 2

11 Soil health indicator: Soil organic C (Soil organic matter) Perennial Cover Cropping with Kura Clover as Alley Crop in Pecan Chariton County, MO % Soil Organic Ma er Kremer & Kussman, Kura Clover Fescue Tilled Crop Kura clover stand in alleys young pecan orchard in September 2006

12 Soil organic matter consists of at least 3 pools of organic matter Active SOM 1 2 yrs C/N ratio Recently deposited organic material Rapid decomposition 10 20% of SOM Considered most sensitive OM indicator of soil health Slow SOM yrs C/N ratio Intermediate age organic material Slow decomposition 10 20% of SOM Passive SOM yrs C/N ratio 7 10 Very stable organic material Extremely slow decomposition 60 80% of SOM 12

13 Active Carbon content for three management systems on Mexico sil, Northeast Missouri. Veum, a a Active C (g/m2) b 20 0 Grass buffer Agroforestry Row Crop Treatments with high biomass and continuous root systems contribute to higher AC and biological activity. [little information on active C contents in cover crop management systems] 13

14 NOTE: Contrast inherent soil quality vs soil quality manipulated via management SOIL HEALTH: continued capacity of soil to function as a vital living system whereby plant and animal growth and environmental quality is sustained; a holistic approach in which plant, animal, and human health is promoted Missouri (Menfro silt loam) Site-specific comparisons limited within a given landscape; Assessment based on management imposed within a landscape; Inherent soil quality is not considered Brazil ( Oxisol )

15 Soil Health is a Comprehensive Assessment Based on Sensitive Indicators Representing all Soil Properties Bulk density* Aggregate stability* Pore size distribution Water-filled pore space* Water-holding capacity* Water-infiltration rate Soil compaction Topsoil depth Physical Biological Chemical Soil Organic Matter (C)* Active C Soil ph* Electrical conductivity (EC)* Cation excange capacity Available P* Exchangeable K* Sodium absorption ratio* Microbial biomass C* Microbial community structure (Biodiversity) Microbial activity Soil enzyme activity (i.e., glucosidase*) Soil respiration (Decomposition rate) Potentially mineralizable N (PMN)* Soil disease suppressiveness Nematode assessment Earthworm assessment Glomalin content *Indicators typically used in soil health index models datasets compiled for these indicators

16 Microbial Diversitydetected using Phospholipid Fatty Acids (PLFA) analysis Structural components of cell membranes in living organisms Represent microbial community structure and biomass population fingerprint Indicate nutritional imbalances and environmental stress in soil microorganism Unger et al. 2012

17 Functional microbial diversity Versatility of mycorrhizae fostered by cover crops Fungal mycelial strands extend plant roots into greater soil volume Contact remote organic substances mineralize P, N, S to return to plant and release for subsequent crops Solubilize P, S, K for plant uptake

18 Mycorrhizae and Cover Crop Implications Faculty of Biology Genetics, University of Munich Lehman et al., 2012 Increased AMF propagules specific for numerous crop host plants

19 Cover Crop weed suppression and soil quality effects Corn and weeds (henbit left) or intercropped w/late summer cover crops (spring oat and berseem clover) Shown 70 days after planting Nov 2012

20 mg root / cm Root density (volume) Oat Henbit Henbit (Oat) 90 days after cover crop seeding

21 Oats as a Cover Crop for Managing Winter Annual Weeds Soil water-stable aggregates Oat cover crop Weed check LSD (0.05)=7.0 Oat cover crop improved soil quality increased soil aggregation and soil microbial activity in addition to suppressing winter annual weeds and potential SCN inoculum potential 0 Soil dehydrogenase activity LSD (0.05)=18 Oat cover crop Weed check 0 umole product/kg soil/h Water-stable aggregates (%) Fall 2005 Spring 2005 Fall 2004 Spring 2004 Fall 2003 Spring 2003 Spring 2002 Fall 2001 Fall 2005 Spring 2005 Fall 2004 Spring 2004 Fall 2003 Spring 2003 Spring 2002 Fall 2001 Kremer, 2005

22 Soil Health root bioassays detect potential seedling pathogens associated with particular cover crop management practices useful in adjusting management strategy Schenck et al ASA Abstracts.

23 Soil Health Index for Assessing Crop Management Systems can be Derived based on selected Soil Health Indicators Example from assessment of various ecosystems within Salt River Basin (Mark Twain Lake watershed) Soil Health Index *Livestock grazing

24 Cover crops - Enhance microbial activity and SOM, improving soil health - important to sustained soil and crop productivity and maintaining the environment - Component of Biological Soil Management that is linked to Soil Health Soil health is considered the major linkage between conservation management practices and achievement of major goals of sustainable agriculture Doran et al STRATEGY: Cover Cropping Residue management Organic recycling Integrated biological management SOIL HEALTH GOAL: Sustainable Production Resource conservation Environmental health Pest suppression Parr et al Am. J. Altern. Agr. 7:5-11

25 Selected References Andrews, S.S., D.L. Karlen, and C.A. Cambardella The soil management assessment framework: a quantitative evaluation using case studies. Soil Sci. Soc. Am. J. 68: Karlen, D.L., G.E. Varvel, J.M.F. Johnson, J.M. Baker, S.L. Osborne, J.M. Novak, P.R. Adler, G.W. Roth, and S.J. Birrell Monitoring soil quality to assess the sustainability of harvesting corn stover. Agronomy Journal 103:288. Karlen, D.L., S.S. Andrews, B.J. Wienhold, and T.M. Zobeck, Soil quality assessment: past, present, and future. J. Integrat. Biosci. 6:3-14. Miles, R.J. and J.R. Brown The Sanborn Field Experiment: Implications for long-term soil organic carbon levels. Agron. J. 103: Stiles, C.A., R.D. Hammer, M.G. Johnson, R. Ferguson, J. Galbraith, T. O Green, J. Arriaga, J. Shaw, A. Falen, P. McDaniel, R.J. Miles Validation testing of a portable kit for measuring an active soil carbon fraction. Soil Sci. Soc. Am. J. 75: Stott, D.E., C.A. Cambardella, R. Wolf, M.D. Tomer, and D.L. Karlen A soil quality assessment within the Iowa River South Fork Watershed. Soil Science Society of America Journal 75: Stott, D.E., S.S. Andrews, M.A. Liebig, B.J. Wienhold, and D.L. Karlen Evaluation of β- glucosidase activity as a soil quality indicator for the Soil Management Assessment Framework (SMAF). Soil Science Society of America Journal 74: