Soil testing

4,100 views

Published on

Lecture developed for my Soil Fertility and Plant Nutrition class in fall 2010

Published in: Education
0 Comments
2 Likes
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
4,100
On SlideShare
0
From Embeds
0
Number of Embeds
10
Actions
Shares
0
Downloads
308
Comments
0
Likes
2
Embeds 0
No embeds

No notes for slide

Soil testing

  1. 1. The art and science of routine soil testinghttp://www.labsafety.com/search/LaMotte/+-1399/24528163/221700/?isredirect=true
  2. 2. What is “routine” soil testing ?
  3. 3. Goals of routine soil testing Rapid Cheap Predictive Broadly applicableVery different from soil science research
  4. 4. Routine soil testing starts with thecollection of "representative" soil samples
  5. 5. How many samples should be collected from each field ? The optimum number of soil samples is a compromise between what should be done (to accurately represent the field) and what can be done (time/cost).120 acre field
  6. 6. What is a composite sample? The U of Illinois currently recommends collecting 1 composite sample per 2.5-acres.120 acre field
  7. 7. Composite sampling Multiple sub- samples are collected fromeach management unit and mixed together
  8. 8. This does not mean that we should all be collecting 20 cores percomposite sample but using only 5 cores per composite is a major compromise.
  9. 9. If we don’t collect enough sub-samples or collect sub-samples at different depths or times… our soil sampling will lack precision Accuracy vs. precision??
  10. 10. Lack of precision in soil sampling = unrepeatable results * * * * How do you know if soil test results are accurate?Inaccurate results => inappropriate fertilizer recommendations
  11. 11. Grid vs. Zone Sampling "Weve been moving in circles for years," says Gyles Randall, soil scientist, University of Minnesota. "Grid sampling was the hottest thing going, but it was expensive. The question was if growers were getting their moneys worth. If land is owned or under a long- term rental agreement, I like grid-based sampling, butunder a short-term rental basis, you can hardly justify it."
  12. 12. Matt Duncan, Key Agricultural Services, Macomb, Ill., is a strong believer in grid sampling. However, it is only one part of the equation. "We foundthat after multiple soil test cycles using grid sampling based variable rate applications, in many cases highs were getting higher and lows were getting lower," says Duncan. "When we looked at the GPS yield data history, we noticed the crop yields were consistently higher in the fieldareas with decreasing soil test values and lower in the areas of increasing soil test levels."
  13. 13. Soil management zones A management zone approach is only possible if knowledge Soil 3 of soil variation is preexisting. Soil Soil 4 1Knowledge of soil variation: County soil survey maps Soil 2 Old field boundariesPast management records
  14. 14. How well do soil survey mapping units relate to crop productivity ? Sometimes very well… other times not so well
  15. 15. Monitoring change over time will be much easier if soil samples are collected from the same locations each time the field is sampled. Sampling locations can be identified using GPSequipment or by more traditional methods such as a measuring wheel. The U of Illinois recommends compositing 5 soilcores from within a 10-foot radius to represent each sampling location.
  16. 16. Important soil sampling considerationsAvoid sampling areas that are clearly not representative (old manure piles, eroded knolls…) Use clean sampling tools Collect samples from a depth that is appropriate for your soil management system: conventional tillage = 6-8” no-till or lawn = 4” Multiple sampling depths (e.g., 0-2” & 2-8”) is often desirable for long term NT systems
  17. 17. Nutrient Stratification and No-till – Is it a problem??
  18. 18. Late summer and fall are often recommended as the best times for collecting soil samples- the soil samples used for soil test correlation are normally collected in the late summer/fall - potassium test results are most reliable during the late summer/fall - nutrient uptake by summer crops has occurred - soil is more likely to be dry Keep in mind that soil testing labs are normally the busiest in the late summer and fall
  19. 19. If possible, sample at ~ the same time every year !
  20. 20. Many labs will only accept samples in official sample bags or boxes
  21. 21. Field moist soil samples should be delivered to a lab ASAP or dried prior to storage
  22. 22. Samples should be accompanied by a submittal form specifyingdesired analyses and crop and soil management information
  23. 23. When samples arrive at a highthroughput lab, they are entered into a tracking system and then prepped for extraction.
  24. 24. Sample prep generally consists of drying and grinding.
  25. 25. Small sub-samples of prepped soils are isolated (normally volumetrically) and then extracted. Extraction is a process ofbriefly washing a soil. It is not intended to simulate the process of root uptake orremove all available nutrients.
  26. 26. A variety of soil extractants areused by soil testing labs in the Midwest region.Examples of extractants: Bray 1, Olsen, Ammonium acetate, Hot water, DTPA, Mehlich 1, Mehlich 3
  27. 27. Mehlich 3 extractant most widely used universal extractant The Mehlich 3 extractant was developed by Dr. Adolph Mehlich to estimate plant availability of macronutrients and micronutrients in soils with a wide range of physical and chemical properties. Adopted by the NCDA soil testing lab in 1981, the Mehlich 3 extractant has reduced analytical costs by replacing multiple extraction methods. Reference: Mehlich A. 1984. Mehlich-3 soil test extractant: a modification of Mehlich-2 extractant. Commun Soil Sci Plant Anal 15(12):1409–16. Composition: (0.2N CH3COOH + 0.25N NH4NO3 + 0.013N HNO3 + 0.015N NH4F + 0.001M EDTA)Would this extracting solution be useful for measuring plant available N?
  28. 28. Ion exchange resins Plant root simulator probes –an alternative method of nutrient extraction
  29. 29. Traditionally sample extracts were analyzedusing different methods for different nutrients but many labs now use sophisticatedinstruments that can analyze many nutrients simultaneously.
  30. 30. Most large labs use an Inductively Coupled Plasma Atomic Emission spectrometer to analyze soil extracts for multiple elements I am an ICP!
  31. 31. By themselves, extractablenutrient levels are not informative.Extractable nutrient levels provide an index of nutrient availability that can be interpreted using results from field experiments.
  32. 32. moisture temperature microbial activity Extractable nutrient levels are notdirectly related to most of the factorscontrolling nutrient availability during a growing season. rooting depth root health
  33. 33. Meaningful interpretation of soil test results requires field calibration100 %yield Field sites are needed that vary widely in soil 50 % test levels of the yield nutrient of interest but have few other limiting factors Soil test P concentration (ppm) http://www.ipm.iastate.edu/ipm/icm/2003/11-17-2003/mehlich3.gif
  34. 34. Relationship between crop yield and soil test K Response curves are derived from calibration data – response curves do not describe all the variation in calibration data !
  35. 35. Rates of P2O5 or K2O to apply based on soil test index value and crop-specific equation * Soil Test IndexEq. # 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 1501 900 780 660 550 460 370 290 220 160 110 70 40 10 0 0 02 500 440 380 330 280 230 190 150 120 90 70 40 30 10 0 03 300 270 230 200 180 150 130 100 80 70 50 40 20 10 10 04 300 260 220 180 150 120 100 70 60 40 30 20 20 20 20 10–305 300 250 210 170 130 100 80 50 30 20 0 0 0 0 0 06 300 240 190 140 100 60 30 10 0 0 0 0 0 0 0 07 250 220 190 160 140 110 90 70 50 40 30 10 0 0 0 08 250 210 160 130 90 60 30 10 0 0 0 0 0 0 0 09 220 190 160 140 120 100 80 60 50 30 20 10 10 0 0 010 200 170 150 120 100 In North Carolina, 25 80 60 50 30 20 10 10 0 0 0 011 200 160 120 90 60 40 20 0 0 0 0 0 0 0 0 012 180 160 140 130 110 different crop response 90 80 70 50 40 30 20 20 10 0 013 165 140 110 90 70 50 30 20 10 0 0 0 0 0 0 014 150 120 100 80 60 equations are used to 40 30 10 0 0 0 0 0 0 0 015 150 120 90 70 40 30 10 0 0 0 0 0 0 0 0 016 150 110 70 40 10 0 make P and K 0 0 0 0 0 0 0 0 0 01718 140 120 120 90 100 60 80 40 70 20 50 0 recommendations 40 0 30 0 20 0 10 0 10 0 0 0 0 0 0 0 0 0 0 019 100 80 70 60 40 30 20 10 0 0 0 0 0 0 0 020 80 60 40 20 0 0 0 0 0 0 0 0 0 0 0 021 20.0 17.0 14.0 11.5 9.5 7.5 5.5 4.0 2.5 1.5 0.5 0 0 0 0 022 11.0 9.5 8.0 7.0 6.0 5.0 4.0 3.0 2.5 2.0 1.0 1.0 0.5 0 0 023 9.0 7.5 6.5 5.5 4.5 3.5 2.5 2.0 1.5 1.0 0.5 0 0 0 0 024 8.0 6.5 5.0 4.0 2.5 2.0 1.0 0 0 0 0 0 0 0 0 025 6.5 5.0 4.0 3.0 2.0 1.0 0.5 0 0 0 0 0 0 0 0 0
  36. 36. Different response equations are used for different crops
  37. 37. Results may be reproducible but havelimited meaning without local field calibration http://www.lamotte.com/
  38. 38. 20 labs actually29 member labsIL 2008 located in in2008 ISTA Members (alphabetical)A KA&L Great Lakes Laboratories, Inc. Key Agricultural ServicesLois K. Parker Dean Wesley3505 Conestoga Dr. 114 Shady LaneFt. Wayne, IN 46808 Macomb, IL 61455Tel: 260-483-4759 Tel: 309-833-1313Fax: 260-483-5274 Fax: 309-833-3993Additional member: Julie Bruggner Additional members: Tad WesleyAgriEnergy Resources KSI LaboratoryGary Cambpell David Brummer21417-1950 E. St. 202 S. Dacey Dr.Princeton, IL 61356 Shelbyville, IL 62565815-872-7790 Tel: 217-774-2421815-872-1928 Fax: 217-774-2866gcampbell@agrienergy.net ksilabdbrummer@consolidated.netAdditional member:Ann Berry - aberry@agrienergy.net M M & R Ag ServicesAgSource Cooperative Services Mick CapouchSteve Peterson 16747 W 200N106 N. Cecil St., PO Box 7
  39. 39. Quality ControlMembers of ISTA are required to participate in a qualitycontrol program referred to as the Split Sample SoilTest Comparison Program. In this process, six samplesare sent quarterly to all member labs. The labs test the soiland return the raw data to an independent accounting firm.This information is then gathered yearly and used in aReliability/Repeatability report. A level of proficiency isrequired to receive a Certificate of Good Standing fromISTA. This certificate is the members accreditation and istheir clients assurance that the information they receive isreliable, consistent and accurate.Some ISTA member labs also participate in an additionalNational Proficiency Testing Program (NAPT).
  40. 40. Good labs include standard (aka check) samples in everyanalytical run. This allows them to quickly identify problems.
  41. 41. Choose a lab and stick with it ! Different labs often use different analytical and interpretation methods
  42. 42. Recommendations Analytical results So what do thenumbers mean ???
  43. 43. Analytical results Recommendations
  44. 44. Analytical results can be obtained without recommendations
  45. 45. Analytical results are commonly presented as concentrations of extractable nutrients (e.g., ppm or lbs/ac) but are sometimes presented as unit-less index values As a general rule, ppm * 2 = lbs/ac (assuming a plow layer weighs 2 million lbs)As stated earlier, by themselves, extractable nutrient levels are not informative. Extractable nutrient levels provide an index ofnutrient availability that can be interpreted using results from field experiments.
  46. 46. Have any of you ever had to run a 40 as part of a try-out for a team? How well does your 40 time predict your ability to play the game?
  47. 47. Turning analytical results into recommendations - the sufficiency approachCritical levels of extractable nutrients have been identified using field experiments The critical levels identified across the US vary because of differences in soilproperties and also because of differences in the interpretation of field experiments
  48. 48. Turning analytical results into recommendations - the sufficiency approachCritical levels of extractable nutrients have been identified using field experiments The critical levels identified across the US vary because of differences in soilproperties and also because of differences in the interpretation of field experiments
  49. 49. Build and maintenance approach Critical Level
  50. 50. Soil is a black box !!!!Maintenance applications of fertilizer(i.e., replacing nutrients removed in harvested crops) make sense conceptually **but** do not necessarily make sense economically !
  51. 51. Regional variation in soil test Khttp://soilfertility.unl.edu/Materials%20to%20include/2001%20NCR%20potassium_files/image008.g if
  52. 52. Changes in soil test results between 2001 and 2005 Some of these trends are a little surprising ! Increased use of conservation tillage may be responsible
  53. 53. http://www.ipni.net/ppiweb/bcrops.nsf
  54. 54. Soil Test KChange between 2005 and 2010 % of samples below critical level
  55. 55. Soil Test PChange between 2005 and 2010 % of samples below critical level
  56. 56. Nutrient balancing conceptsNutrients interact in plant and soil systems. Someimportant nutrient interactions include ammonium-calcium, phosphorus-iron, phosphorus-copper,phosphorus-zinc, and potassium-magnesium-calcium.Some consultants and private labs place greatemphasis on “base cation ratios”.Typical target ratios: 65-75% Ca : 10-15% Mg : 2-5% K
  57. 57. Nutrient interactions and proper nutrient balance should be considered in relation to nutrient supply – i.e. the availability of nutrients in the soil. Nutrient supply is important because “recommended nutrient ratios" in soil or plant tissue are possible even when nutrients are deficient or excessively high. As we have discussed earlier in the semester, nutrient imbalance can be a problem (e.g., competitive ion effects and other types of antagonistic nutrient interactions) butnutrient balance in animal diets is probably more importantthan in soil because of the selective abilities of plant roots
  58. 58. Some day soon soil testing may consist ofon-the-fly “sensing” of soil hundreds tothousands of times per acre like a yield monitor
  59. 59. http://bse.unl.edu/adamchuk/presentations/
  60. 60. ahttp://bse.unl.edu/adamchuk/presentations/
  61. 61. “The Soil Doctor”The original electrical conductivity/resistivity system
  62. 62. http://bse.unl.edu/adamchuk/presentations/
  63. 63. 2.5 acre grid sampling vs.high density on the fly sensing
  64. 64. http://bse.unl.edu/adamchuk/presentations/
  65. 65. http://bse.unl.edu/adamchuk/presentations/
  66. 66. http://bse.unl.edu/adamchuk/presentations/
  67. 67. http://bse.unl.edu/adamchuk/presentations/
  68. 68. http://bse.unl.edu/adamchuk/presentations/
  69. 69. Soil pH and lime requirement often vary widely within fields Is a high density pH map all you need for variable rate lime application?
  70. 70. Variable rate P and K is based on false Variable rate is only assumptions and does not pay. I likely to pay in fields only do variable with large variability rate lime on my including levels farm now. above and below critical levels. Illinois corn and soybean producer Ken Dalenberg (Mansfield IL) was recently named 2010 Farmer of the Year in the PrecisionAg Awards OfExcellence program. His deliberate approach to honest evaluation has helpedhim build relationships with universities and industry… he is frequently involvedin advanced evaluation of equipment for John Deere and other companies. He is frequently invited to speak at conferences throughout the U.S. and other countries. Ken understands the importance of proper scientific methodologyand is willing to expend the extra efforts and costs to do it right…even though it means delays in getting his farm work done.”
  71. 71. MISS has incorporated EC, NDVI readers and soil testing so that the client can restassured that low application amounts prior to planting will not hurt the crop yield. By going a step further and taking stalk nitrate tests at those same locations of soil testing, the client is able to further define the management map and customize the following nitrogen applications to occur.

×