Assessing Soil Health in Missouri Agricultural Soils Kristen Veum Robert Kremer Keith Goyne

1. Assessing Soil Health in Missouri Agricultural SoilsKristen Veum Robert KremerKeith Goyne Soil Health Workshop. Bradford Extension and Research Center. Oct. 8, 2013

2. Soil Sampling ConsiderationsWhen, Where, How, & Why • Why?Most important consideration. • When? • Time of year (seasonal, management activities) • Across years (trends) • Where? • Management Practice Comparisons & Reference Soil Comparisons (fence row, uncultivated soil) • Landscape Position / Landforms / Soil types • Rhizosphere, Depth differences • How? • Soil sampling and handling/storage protocols

3. Biological Soil Properties Biological properties can change rapidly (dynamic): • Spatially • Depth – generally decline with depth • Landscape (rhizosphere, hillslope) • Temporally • Season • Crop and other management activities • Climate differences (i.e., drought years) • Short-term and long-term trends

4. What is a soil quality/health index? • Goal: Translating soil properties into a soil quality or soil health score. • How? • Measure important soil properties (i.e., soil health indicators) • Assign a score based on relationships with soil functions (water infiltration, crop productivity, etc…). • General Categories: More is Better, Less is Better, Optimal Value • The scores are combined into one final number. • Each existing soil health index uses a unique set of soil properties and a unique way of scoring soil health. Some are quantitative, some are very subjective. Many are region-specific.

5. Soil Quality/Health Indices • Soil Management and Assessment Framework (SMAF) soil quality index • Cornell Soil Health Test (CSHT) • Assessing Agronomic and Environmental Performance of Management Practices in Long-Term Agroecosystem Experiments (AEPAT) • Soil Conditioning Index (SCI) • Biological Quality of Soil (QBS) • CCME Soil Quality Index (SoQI) • Forest Soil Quality Index (FSQI)

6. The Soil Management Assessment Framework (SMAF) soil quality index • Scores based on data linking soil indicators to soil functions, such as crop productivity, water infiltration, and environmental protection. • Based on site-specific characteristics that account for important factors such as crop, climate, soil texture, mineralogy, etc. • 13 indicators representing 4 soil function groups: • Physical – aggregate stability, bulk density, water filled pore space, available water capacity • Chemical – electrical conductivity, pH • Nutrient – P, K, Na adsorption ratio • Biological – SOC, microbial biomass-C, β-glucosidase, mineralizable N

7. SMAF Example: Centralia Plots (2008) 5 Cropping Systems (since 1991): • Minimum Till Corn – No Till Soybean (MTC-NTS) • No Till Corn – No Till Soybean (NTC-NTS) • Integrated Crop Mgt - Wheat (cover) - Corn (cover) – Soybean (ICM-WCS) • Switchgrass formerly intensively cropped (SG) • Cool-season grass & legume (CRP) 3 Landscape Positions: • Summit, Backslope, and Toeslope

8. SMAF Example: Centralia Plots 6 SMAF Indicators Selected (of 13) **You do not need to measure all possible indicators in order to use an index • Soil Organic Carbon • Extractable Phosphorus • Extractable Potassium • Water pH • Bulk Density • Water Stable Aggregates

9. Centralia SMAF Scores byLandscape Position Clear landscape position differences in SMAF scores

10. Soil Organic Carbon (SOC) • Measure of organic matter • Source of many important nutrients • Affects cation exchange capacity, water holding capacity, soil aggregation, etc. • Considered a ‘keystone’ soil health property

11. Soil Organic Carbon: Cropping SystemsMeasured Values and SMAF scores Clear effects of cropping system in SOC data and SMAF SOC scores. CRP has highest SOC and SOC score. The switchgrass still reflects the degradation from previous intensive management

12. Soil Organic Carbon: Landscape PositionsMeasured Values and SMAF scores Clear effects of landscape position in SOC data and SMAF SOC scores The increased clay content of the backslope changes soil texture and affects the SMAF score

13. Microbial Enzyme Activity • measures the function of the microbial community • reflects the quantity and quality of available substrates • different enzymes represent decomposition and cycling of different nutrients • phosphatase – phosphorus • nitrogenase – fix nitrogen • dehydrogenase – overall microbial activity • β-glucosidase– breakdown of cellulose, etc.

14. β-Glucosidase: Cellulose degradationMeasured Values and SMAF scores Clear effects of cropping system from disturbance The “more is better” concept translates greater enzyme activity into higher SMAF scores CRP>Cover>No-till>= SWG>MinTill

15. Water Stable Aggregates • Reflects soil structure and resistance to erosion, slaking, etc. • Tends to be stronger with increased clay and organic matter • Extremely important for water infiltration, aeration, etc.

16. Water Stable Aggregates:Measured Values and SMAF scores Clear effects of cropping system in aggregate stability. Trend relates to soil disturbance SMAF scores all fairly high. This is due to the way SMAF scores aggregate stability.

17. Water Stable Aggregates:Measured Values and SMAF scores Clear effects of landscape position in aggregate stability. Clay and organic matter are important in soil aggregation. The scores reflect the SMAF algorithm…..

18. Bulk Density • Increases with compaction from traffic -- can increase with no-till compared to conventional tillage • Increased bulk density is associated with reduced aeration and water infiltration

19. Bulk DensityMeasured Values and SMAF scores The “less is better” concept translates greater bulk density into lower SMAF scores. Switchgrass has the highest bulk density due to previous intensive cropping practices

20. Overall SMAF Scores by Cropping System

21. Mineralizable Nitrogen • Is a subset of total N • Sometimes called the ‘active N fraction’ • Supplies N for crop growth

22. Mineralizable Nitrogen: By DepthMeasured Values and SMAF scores Centralia (2010 data): Surface 0-10 inches Subsurface 10-20 inches Depth differences for raw data and SMAF scores. Illustrates the decline in biological properties with depth. Consider how perennial vegetation differs from annual cropping systems…

23. Does the SMAF Work?Sanborn Field Example Veum et al. 2013 (Biogeochemistry)

24. Why can’t we just measure one variable for soil health? • Each soil health indicator tells us something important about the soil • A soil may perform some functions well but not others • Together, the soil health indicators tell a more comprehensive story about the soil • Necessary to make more informed management decisions.

25. Many Important Variables not currently in the SMAF or other soil health indices • Active C • Cornell Soil Health Test • Phospholipid Fatty Acids (PLFA) • tomorrow’s talk • Other microbial enzymes • Need more biological variables in soil health indices

26. Selected SMAF References • Stott, D.E., C.A. Cambardella, R. Wolf, M.D. Tomer, and D.L. Karlen. 2011. A soil quality assessment within the Iowa River South Fork Watershed. Soil Science Society of America Journal 75:2271-2282. doi:10.2136/sssaj2010.0440. • Stott, D.E., S.S. Andrews, M.A. Liebig, B.J. Wienhold, and D.L. Karlen. 2010. Evaluation of β-glucosidase activity as a soil quality indicator for the Soil Management Assessment Framework (SMAF). Soil Science Society of America Journal 74:107-119. doi:10.2136/sssaj2009.0029. • 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. 2011. Monitoring soil quality to assess the sustainability of harvesting corn stover. Agronomy Journal 103:288. doi:10.2134/agronj2010.0160s.