Soil Health Tests How useful are they on Indiana croplands?

Transcription

1 12/13/217 Soil Health Tests How useful are they on Indiana croplands? Dr. Stacy Zuber Dr. Eileen Kladivko Agronomy Dept., Purdue University (and a cast of hundreds across the state and region!) Overall Goal Improve soil health! Soil conservation, productivity Crop productivity, resilience to climate variations Water quality Economics (profitability) Soil Health Systems Groups of practices put together in coherent way Practices include cover crops, no-till, nutrient and pest mgmt., etc. Soil health focuses on integration of soil biology, fertility, and physical properties But how do we measure it? Integrated soil health tests are new Biology is especially difficult to assess Physical properties also difficult Fertility (chemical) tests well established for decades Once measured, what does it mean? Biology not well understood so many organisms, interactions, redundancy, dynamic changes w/ weather, food,. December 217 Indiana CCA Conference 1

2 12/13/217 Why want to measure it? So we know the most important constraints to be addressed in a field Then to guage changes (improvements) with time, as change management To have index of overall health or functioning of a field To monitor long-term, much like standard soil fertility testing CCSI Cons.Innov.Grant (CIG) We were getting lots of questions about new soil biology/soil health tests, from farmers, conservation partners, etc. How useful might those tests be? Could they distinguish different mgmt. systems? Could they monitor change over time? Would they be worth the cost ($$$) for Indiana conditions? CCSI Conservation Innovation Grant (CIG) project 17 sites across IN 12 farmer sites 3 Purdue Ag Centers 2 others Most sites have cover vs. no cover strips Most sites are longterm no-till Most covers are single species, but a few are mixes, esp. after wheat DTC DeSutter Brocksmith Rulon SEPAC NEPAC Alford Goals Educate farmers, conservation partners, about cover crops, no-till, other. Utilize farmer cooperators as teachers, mentors, and hosts of demo projects Evaluate commercial soil health tests for potential usefulness on Indiana farms Measurements made in CCSI project Cover crop growth (biomass), N%, N content in biomass, fall and spring Soil nitrate/ammonium-n(fall, spring, PSNT), std fertility (A&L), temp, moisture, four commercial soil health tests Some sites w/ sensors for temp and moisture; aggregation, penetration, bulk density, water retention curve (water holding capacity) Cash crop yield (corn also SPAD, stalk nitrate) December 217 Indiana CCA Conference 2

3 12/13/217 Commercial soil health tests PLFA (Phospholipid Fatty Acid) Earthfort Soil Food Web Haney Soil Health Nutrient Tool (CO2 burst) Cornell Soil Health test The first two are biological tests. Third is biological and chemical. Interpretations still in their infancy, as there is no standard like w/ fertility test. Cornell test includes biol., phys., and chem. Findings so far Cover crop biomass varies greatly across sites and years, of course ~71 lb/a ~25 lb/a Findings so far Cover crop biomass varies greatly across sites and years, of course Soil nitrate in spring right before cover crop termination, is generally lower in cover crop plots than in controls (no cover crop). Cover crop has scavenged N from soil, protecting it against loss. 7 Month Brown Gap for soybean and corn, fallow period Cover crop grows and takes up N during some of that normally fallow season. This would shrink the brown gap and keep the land green for longer time. Tile drain studies in Midwest consistently show reduction in nitrate leaching with cover crops This scavenged N goes into YOUR soil N bank account! December 217 Indiana CCA Conference 3

4 12/13/217 Phospholipid Fatty Acid Analysis (PLFA) Biochemical marker Total is indicator of total viable biomass Biomarkers unique to broad classifications in soil biology Earthfort Laboratory Soil Dilutions - Direct microscopy Active bacteria / fungi : Fluorescein diacetate (binds to metabolically active bacteria and fungi) Total bacteria: Fluorescein isothiocyanate Total fungi and protozoa no stain used Highly variable (+/- 2%) png Statistically Significant Differences High variability in the measurements makes it difficult to detect statistically significant differences. Treatment Rep #1 Rep #2 Rep #3 Rep #4 Average NT+CC NBR Soil Health Results Results shown are from 14 on-farm sites. Most are from 216, but Earthfort results are from 215 (Earthfort test was not used in 216). Each site had different management practices and treatments. More details are found in the individual site reports on the CCSI website. December 217 Indiana CCA Conference 4

5 12/13/217 Treatment Abbreviations NT+CC No-till plus cover crop NT No-till, no cover crop ST+CC Strip-till plus cover crop ST Strip-till, no cover crop CT+CC Tillage plus cover crop NBR conventional neighbor tillage, no cover PLFAs (nmol/g) PLFA: Total Microbial Biomass Represents overall size of living microbial community Significant differences between treatments at a site are indicated by red boxes around treatment abbreviation or by letters. Brocksmith (SW) Mills (NW) Scott VUJC (SW) Wenning (SE) Mycorrhizal Fungi PLFA: Mycorrhizal Fungi Can form beneficial relationship with crop roots. Help scavenge for N and P. PLFAs (nmol/g) AB A B C.5 Alford (SE) DeSutter (NW) Huffmeyer (SE) Rulon (NW) ology/?cid=nrcs142p2_53864 December 217 Indiana CCA Conference 5

6 12/13/217 PLFAs (nmol/g) PLFA: Protozoa Predators of bacteria & messy eaters Excess N is released to soil in plantavailable forms 216 Earthfort: Protozoa Earthfort identifies three different types of protozoa. Flagellates Smallest type of protozoa. Amoeba Ciliates Largest and least numerous Shuter Villwock (SW) Wabash SWCD Werling Flagellates Amoeba Ciliates Earthfort: Protozoa µg/g µg/g µg/g NT+AR NT+CR NT+O/R NT+CC NT NT+CC NT Rulon (NW) Stahl (SW) Villwock (SW) NT+AR NT+CR NT+O/R NT+CC NT NT+CC NT Rulon (NW) Stahl (SW) Villwock (SW) NT+AR NT+CR NT+O/R NT+CC NT NT+CC NT Rulon (NW) Stahl (SW) Villwock (SW) PLFA: Diversity Index Diversity Index High diversity is very good for soil health. Need different types of microbes to perform all soil functions EX: Fungi-enzymes to break down complex molecules in residues, aggregate formation; Protozoa-bacterial feeders December 217 Indiana CCA Conference 6

7 12/13/ PLFA: Diversity Index Higher values indicate larger numbers of fungi and protozoa. Not as bacteria-dominated. 216 Carbon & Nutrient Cycling Measurements in Cornell and Haney tests Active C and Water Extractable Organic C Both measure fraction of soil organic matter that is easy for microbes to use. Food for microbes Releases nutrients Soil Respiration Measures potential activity of microbes in soil. How much CO 2 released in 96 hours. Shuter Villwock (SW) Wabash SWCD Wenning (SE) Active C Water Ext. Organic C Soil Resp. (96 hrs) Carbon & Nutrient Cycling ppm ppm ppm NT+CC NT NBR NT+CC NT NBR NT+CC NT NBR NT+CC NT NBR NT+CC NT NBR NT+CC NT NBR Brocksmith (SW) DeSutter (NW) 216 Overall Soil Health Index Cornell Quality Score Haney Soil Health Calculation Both are calculated from multiple soil health indicators. Including some soil fertility, which is often very good for both treatments, given farmers typical priorities obscures other differences Averaging multiple indicators doesn t show which soil functions can still be improved Overall few differences were detected December 217 Indiana CCA Conference 7

8 12/13/217 Summary Overall, few differences between cover and no cover treatments. Most sites had long-term no-till in place Only 2-3 years of cover crops More differences detected between CCSI plots and the neighboring field. Some complications with soil textural differences and agronomic management (cash crop, manure, etc.). Remember the goals of project. We were getting lots of questions about new soil biology/soil health tests, from farmers, conservation partners, etc. How useful might those tests be? Could they distinguish different mgmt. systems? Could they monitor change over time? Would they be worth the cost ($$$) for Indiana conditions? Potential usefulness of these tests Limitations to the tests themselves, as used in this project (could not necessarily distinguish treatments that appear in field to be different). Don t necessarily capture important aspects of field soil functioning. Limitations related to short-term study, with covers only ~2-3 yrs on base of long-term notill (ie don t expect big change). Limitations based on experimental design and protocols; many varying factors. Biology testing variations Timing of sampling in season late May to August Recent weather cold, hot, rain, dry (Cash) crop growing at that time, stage, etc. (ie sampled recent wheat stubble, vs growing beans; or growing wheat vs. young soybean; or C vs S) Specific locations within field wheel track, how close to cash crop and cover crop rows, landscape position, residue cover. Strip-till as extreme example. Sample depth -8 ; probably more effects -4 December 217 Indiana CCA Conference 8

9 12/13/217 Further analyses planned If we are not able to detect many differences in a snapshot, are there soil health indicators showing a positive trend over time? Are there other factors (SOM, soil texture, climate, cover crop species) that influence our results? Challenges, future needs Longer time in the soil health system Start with conventional system and measure changes over time Further development of calibrations and interpretations of commercial soil health tests Economics beyond case studies How assess other attributes we observe but are too difficult to measure? How assign a score or importance value? Individual Site Reports are available on CCSI website: Additional Summary Report will be available in January 218. Thank you! Cereal rye, SE Indiana December 217 Indiana CCA Conference 9