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Soil testing
- 1. The art andscience of routine soil testing http://www.labsafety.com/search/LaMotte/+-1399/24528163/221700/?isredirect=true
- 2. What is “routine” soil testing ?
- 3. Goals of routinesoil testing Rapid Cheap Predictive Broadly applicable Very different from soil science research
- 4. Routine soil testingstarts with the collection of "representative" soil samples
- 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. What is a composite sample? The U of Illinois currently recommends collecting 1 composite sample per 2.5-acres. 120 acre field
- 7. Composite sampling Multiple sub- samples are collected from each management unit and mixed together
- 8. This does notmean that we should all be collecting 20 cores per composite sample but using only 5 cores per composite is a major compromise.
- 9. If we don’tcollect enough sub-samples or collect sub-samples at different depths or times… our soil sampling will lack precision Accuracy vs. precision??
- 10. Lack of precisionin soil sampling = unrepeatable results * * * * How do you know if soil test results are accurate? Inaccurate results => inappropriate fertilizer recommendations
- 11. Grid vs. ZoneSampling "We've 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 money's worth. If land is owned or under a long- term rental agreement, I like grid-based sampling, but under a short-term rental basis, you can hardly justify it."
- 12. Matt Duncan, KeyAgricultural Services, Macomb, Ill., is a strong believer in grid sampling. However, it is only one part of the equation. "We found that 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 field areas with decreasing soil test values and lower in the areas of increasing soil test levels."
- 13. Soil management zones A management zone approach is only possible if knowledge Soil 3 of soil variation is preexisting. Soil Soil 4 1 Knowledge of soil variation: County soil survey maps Soil 2 Old field boundaries Past management records
- 14. How well dosoil survey mapping units relate to crop productivity ? Sometimes very well… other times not so well
- 15. Monitoring change overtime 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 GPS equipment or by more traditional methods such as a measuring wheel. The U of Illinois recommends compositing 5 soil cores from within a 10-foot radius to represent each sampling location.
- 16. Important soil samplingconsiderations Avoid 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. Nutrient Stratification andNo-till – Is it a problem??
- 18. Late summer andfall 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. If possible, sampleat ~ the same time every year !
- 20. Many labs willonly accept samples in official sample bags or boxes
- 21. Field moist soilsamples should be delivered to a lab ASAP or dried prior to storage
- 22. Samples should beaccompanied by a submittal form specifying desired analyses and crop and soil management information
- 23. When samples arriveat a high throughput lab, they are entered into a tracking system and then prepped for extraction.
- 24. Sample prep generallyconsists of drying and grinding.
- 25. Small sub-samples ofprepped soils are isolated (normally volumetrically) and then extracted. Extraction is a process of briefly washing a soil. It is not intended to simulate the process of root uptake or remove all available nutrients.
- 26. A variety ofsoil extractants are used by soil testing labs in the Midwest region. Examples of extractants: Bray 1, Olsen, Ammonium acetate, Hot water, DTPA, Mehlich 1, Mehlich 3
- 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. Ion exchange resins Plant root simulator probes – an alternative method of nutrient extraction
- 29. Traditionally sample extractswere analyzed using different methods for different nutrients but many labs now use sophisticated instruments that can analyze many nutrients simultaneously.
- 30. Most large labsuse an Inductively Coupled Plasma Atomic Emission spectrometer to analyze soil extracts for multiple elements I am an ICP!
- 31. By themselves, extractable nutrientlevels are not informative. Extractable nutrient levels provide an index of nutrient availability that can be interpreted using results from field experiments.
- 32. moisture temperature microbial activity Extractable nutrient levels are not directly related to most of the factors controlling nutrient availability during a growing season. rooting depth root health
- 33. Meaningful interpretation ofsoil test results requires field calibration 100 % 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. Relationship between cropyield and soil test K Response curves are derived from calibration data – response curves do not describe all the variation in calibration data !
- 35. Rates of P2O5or K2O to apply based on soil test index value and crop-specific equation * Soil Test Index Eq. # 0 10 20 30 40 50 60 70 80 90 100 110 120 130 140 150 1 900 780 660 550 460 370 290 220 160 110 70 40 10 0 0 0 2 500 440 380 330 280 230 190 150 120 90 70 40 30 10 0 0 3 300 270 230 200 180 150 130 100 80 70 50 40 20 10 10 0 4 300 260 220 180 150 120 100 70 60 40 30 20 20 20 20 10–30 5 300 250 210 170 130 100 80 50 30 20 0 0 0 0 0 0 6 300 240 190 140 100 60 30 10 0 0 0 0 0 0 0 0 7 250 220 190 160 140 110 90 70 50 40 30 10 0 0 0 0 8 250 210 160 130 90 60 30 10 0 0 0 0 0 0 0 0 9 220 190 160 140 120 100 80 60 50 30 20 10 10 0 0 0 10 200 170 150 120 100 In North Carolina, 25 80 60 50 30 20 10 10 0 0 0 0 11 200 160 120 90 60 40 20 0 0 0 0 0 0 0 0 0 12 180 160 140 130 110 different crop response 90 80 70 50 40 30 20 20 10 0 0 13 165 140 110 90 70 50 30 20 10 0 0 0 0 0 0 0 14 150 120 100 80 60 equations are used to 40 30 10 0 0 0 0 0 0 0 0 15 150 120 90 70 40 30 10 0 0 0 0 0 0 0 0 0 16 150 110 70 40 10 0 make P and K 0 0 0 0 0 0 0 0 0 0 17 18 140 120 120 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 0 19 100 80 70 60 40 30 20 10 0 0 0 0 0 0 0 0 20 80 60 40 20 0 0 0 0 0 0 0 0 0 0 0 0 21 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 0 22 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 0 23 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 0 24 8.0 6.5 5.0 4.0 2.5 2.0 1.0 0 0 0 0 0 0 0 0 0 25 6.5 5.0 4.0 3.0 2.0 1.0 0.5 0 0 0 0 0 0 0 0 0
- 36. Different response equationsare used for different crops
- 37. Results may bereproducible but have limited meaning without local field calibration http://www.lamotte.com/
- 39. 20 labs actually29member labsIL 2008 located in in 2008 ISTA Members (alphabetical) A K A&L Great Lakes Laboratories, Inc. Key Agricultural Services Lois K. Parker Dean Wesley 3505 Conestoga Dr. 114 Shady Lane Ft. Wayne, IN 46808 Macomb, IL 61455 Tel: 260-483-4759 Tel: 309-833-1313 Fax: 260-483-5274 Fax: 309-833-3993 Additional member: Julie Bruggner Additional members: Tad Wesley AgriEnergy Resources KSI Laboratory Gary Cambpell David Brummer 21417-1950 E. St. 202 S. Dacey Dr. Princeton, IL 61356 Shelbyville, IL 62565 815-872-7790 Tel: 217-774-2421 815-872-1928 Fax: 217-774-2866 gcampbell@agrienergy.net ksilabdbrummer@consolidated.net Additional member: Ann Berry - aberry@agrienergy.net M M & R Ag Services AgSource Cooperative Services Mick Capouch Steve Peterson 16747 W 200N 106 N. Cecil St., PO Box 7
- 41. Quality Control Members ofISTA are required to participate in a quality control program referred to as the Split Sample Soil Test Comparison Program. In this process, six samples are sent quarterly to all member labs. The labs test the soil and return the raw data to an independent accounting firm. This information is then gathered yearly and used in a Reliability/Repeatability report. A level of proficiency is required to receive a Certificate of Good Standing from ISTA. This certificate is the member's accreditation and is their clients' assurance that the information they receive is reliable, consistent and accurate. Some ISTA member labs also participate in an additional National Proficiency Testing Program (NAPT).
- 42. Good labs includestandard (aka check) samples in every analytical run. This allows them to quickly identify problems.
- 44. Choose a laband stick with it ! Different labs often use different analytical and interpretation methods
- 45. Recommendations Analytical results So what do the numbers mean ???
- 46. Analytical results Recommendations
- 47. Analytical results canbe obtained without recommendations
- 48. Analytical results arecommonly 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 of nutrient availability that can be interpreted using results from field experiments.
- 49. Have any ofyou 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?
- 50. Turning analytical resultsinto recommendations - the sufficiency approach Critical levels of extractable nutrients have been identified using field experiments The critical levels identified across the US vary because of differences in soil properties and also because of differences in the interpretation of field experiments
- 51. Turning analytical resultsinto recommendations - the sufficiency approach Critical levels of extractable nutrients have been identified using field experiments The critical levels identified across the US vary because of differences in soil properties and also because of differences in the interpretation of field experiments
- 52. Build and maintenanceapproach Critical Level
- 53. Soil is ablack box !!!! Maintenance applications of fertilizer (i.e., replacing nutrients removed in harvested crops) make sense conceptually **but** do not necessarily make sense economically !
- 54. Regional variation insoil test K http://soilfertility.unl.edu/Materials%20to%20include/2001%20NCR%20potassium_files/image008.g if
- 55. Changes in soiltest results between 2001 and 2005 Some of these trends are a little surprising ! Increased use of conservation tillage may be responsible
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- 58. Soil Test K Changebetween 2005 and 2010 % of samples below critical level
- 59. Soil Test P Changebetween 2005 and 2010 % of samples below critical level
- 61. Nutrient balancing concepts Nutrientsinteract in plant and soil systems. Some important nutrient interactions include ammonium- calcium, phosphorus-iron, phosphorus-copper, phosphorus-zinc, and potassium-magnesium-calcium. Some consultants and private labs place great emphasis on “base cation ratios”. Typical target ratios: 65-75% Ca : 10-15% Mg : 2-5% K
- 62. Nutrient interactions andproper 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) but nutrient balance in animal diets is probably more important than in soil because of the selective abilities of plant roots
- 63. Some day soon soil testing may consist of on-the-fly “sensing” of soil hundreds to thousands of times per acre like a yield monitor
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- 66. “The Soil Doctor” Theoriginal electrical conductivity/resistivity system
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- 69. 2.5 acre gridsampling vs. high density on the fly sensing
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- 75. Soil pH andlime requirement often vary widely within fields Is a high density pH map all you need for variable rate lime application?
- 78. Variable rate Pand 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 Of Excellence program. His deliberate approach to honest evaluation has helped him build relationships with universities and industry… he is frequently involved in 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 methodology and is willing to expend the extra efforts and costs to do it right…even though it means delays in getting his farm work done.”
- 81. MISS has incorporatedEC, NDVI readers and soil testing so that the client can rest assured 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.