Soil Analysis: Sampling, Accuracy and Maps

Transcription

1 Soil Analysis: Sampling, Accuracy and Maps Robert O. Miller Colorado State University Fort Collins, CO Indianapolis, IN December 18, Miller, 2018

2 My Background 5 th Generation farm family in eastern Nebraska 500 acres corn and soybeans. Affiliate Professor Colorado State University. - Extension Soil Specialist UC Davis - Ph.D. Montana State University Direct the Agricultural Laboratory Proficiency (ALP) Program, 118 labs. Conduct Regional Research in soil sampling, soil fertility, lab analysis and crop nutrition.

3 Overview Field sample soil composite Grid point sampling Grid sampling intensity Cost of Soil Testing Certified Soil Test Labs

4 The Soil Testing Chain Soil Sample Test Method Calibration Database Soil Testing is based on three components, each linked to make an accurate recommendation.

5 Soil Sampling Field Composite Soil sampling has a long history which started with small plots on University research stations. Cyril Hopkins, Univ of Illinois Dept of Agronomy, and James H.Pettit (left), the Morrow Plots,1900. The traditional whole field approach is to collect a composite sample based on individual cores. Miller, 2018

6 Number of Cores? Number of cores composited 60 Hailin Zhang, Oklahoma State Univ, 2003 Precision improves with cores 120 Swenson et al, 1984 NO3-N NO3-N (lbs/ac) Weighted Mean Number of Sample Cores in Composite Number of Subsamples Level of precision +/- (% Stdev of mean)

7 Soil Phosphorus Field Variability Weighted Average and RSD Field #16, 40 ac No Till 15 yrs 30 Mean Concentration RSD % 70 N 45 Mean 21.8 Bray P1 (ppm) RSD (%) Stdev 9.9 RSD % 45 Confidence Interval (CI) ± Number Bray P1 (ppm) Bray P1 - Field 16 NE Number of Samples Miller, 2018

8 STP (Bray) Field Variability STP Weighted Average 80 Wt. Mean Concentration RSD (%) Wt. Mean Concentration RSD (%) Wt. Mean Concentration RSD (%) Bray P1 (ppm) RSD (%) Number Bray P 1 (ppm) 50 Bray P1 - Field 53 IL Bray P1 - Field 345 IL Bray P1 - Field 47 IA Number of Samples Number of Samples Number of Samples Cores 27 Cores 31 Cores 26 Mean 63.5 Mean 54.7 Mean 53.2 Stdev 26.0 Stdev 20.7 Stdev 19.1 RSD % 41 RSD % 38 RSD % 36 Miller, 2018

9 Field Composite Soil Test Variability 142 fields across Midwest, three soil test parameters Statistic ph STP STK Mean Range RSD % Range Median RSD % Source: Miller Farms, Harvest land co-op, Riverland FS Inc, Rock River Labs, SGS Mowers, United Soils, GMS Labs, Inc., Maxi Yield Coop, Growmark, Midwest Independent Soil Samplers, LGI Lab, MVTL, Soil View, and Frontier Labs.

10 Grid Point Soil Sampling Grid sampling involves collecting soils at geo referenced locations based on, combining multiple cores. 1.1, 2.5or 4.4 ac/grid point. The soil test is only as good as the quality sampling point composite. How many cores?

11 Grid Point Sampling Project Seventy-two fields across ten states were selected. 10 ft At a random grid point, 12 cores were removed in a structured pattern within a 10 ft radius of center, individually analyzed in triplicate for ph, Buffer ph, P, K, NO3-N, Zn and SOM. 10 ft J Ellsworth, Wilbur Ellis, Approx scale

12 Grid Point Sampling Field #16 (Gretna, NE): No-Till 8 yrs Silt loam, 0-3% slope 10 ft Approx scale LGI Labs, IA November 2006 Bray P1 (ppm) Position Mean 17.0 Stdev 4.8

13 Field #16 Bray P1 (ppm) Cores Composited? Position Count Bray P1 (ppm) 19.3 Cores Selected 2 of 12 3 of 12 6 of 12 8 of of Combinations LGI Labs, IA November 2006

14 Grid Point Cores - Bray P1 Field #16: Core Combination Results Bray P1 2 of 12 Cores 4 of 12 Cores 6 of 12 Cores 8 of 12 Cores 12 Cores Combinations Min Mean (ppm) Max Mean (ppm) Range RSD % Based on soil core combinations.

15 Grid Point Cores - Bray P1 Field #16 - No Till Field, RSD 28% 8 ft 6 8 ft Approx scale 30 Mean P Concentration Range Selecting 4 cores of 12 results in mean Bray P1 range ppm. Bray P1 (ppm) of 12 cores results in mean Bray P1 range of ppm /12 4/12 6/12 8/12 11/ Number of Cores

16 Can More Cores Improve Precision for No Till No Till Increasing the number of sub 40 Wt Mean Conc RSD (%) 120 samples beyond 12 cores at a highly variable site, does not significantly improve the estimate of the average or reduce the Bray P1 (ppm) RSD (%) variance for P. Cores NE - Field # Mean 14.1 Stdev 8.7 RSD % 58 Number of Samples STP Weighted Average

17 Grid Point Sample Radius The sampling radius of the grid point impacts the soil test measurement precision. Analysis 10 ft Radius 100 ft Radius mean RSD% mean RSD% ph P (ppm) K (ppm) CEC (cmol/kg) SOM (%) Based on 12 individual cores collected at Harcourt, IA site, Min till, fall Soil Tests Mehlich 3.

18 Field Grid Pt Variability Bray P Grid Point mg kg-1 RSD (%) Indiana, No-Till, 21 Grid points, each sampled with 12 individual cores, 10 ft radius Within a field Bray P ranged from ppm while the RSD varied from 16 74%. Sampled by Dave Taylor Harvest Coop, Winchester, IN STP STP

19 Phosphorus Bray P1 8 ft Grid Point RSD Approx scal 72 Sites, Across Ten States Field Mgt No-Till Min-Till Conv. Manured # Sites Range RSD (%) Median RSD (%) Based on 72 sites, A&L Great Lakes, United Soils and LGI November,

20 Phosphorus K 8 ft Grid Point RSD Approx scale 72 Sites, Across Ten States Field Mgt No-Till Min-Till Conv. Manured # Sites Range RSD (%) Median RSD (%) Based on 72 sites, A&L Great Lakes, United Soils and LGI November,

21 One last Point P Soil Stratification Strip-till systems show high surface stratification of P. Sampling depth becomes critical. Soil sampling 0-8 results in high bias soil test P. Depth adjusted P: 0 8 Depth: 24 mg kg Depth: 12 mg kg -1 { 24 mg kg -1 Depth (in) John Groves, Presentation at 11:00 and 4:00 today. Soil: Hastings silt loam, Kearney, NE. Field #177, NE: No-Till, Bray P

22 Grid Point Observations Grid point soil test variability (RSD) generally follows: STP > Soil NO 3 -N > STK > SOM > ph. At No-till sites Bray P concentration variability is high across distances < 20 feet. Soil Test P variation increases with decreasing tillage, stratification and lower soil test levels.

23 Manage Your Soil Sampling Number of Cores With decreased tillage, increase the number of cores, to improve accuracy and precision cores per grid point most effective Conventional No Till Decreased Tillage

24 Overview Field sample soil composite Grid point sampling Grid sampling intensity Cost of Soil Testing Certified Soil Test Labs

25 8 ft Grid sampling intensity Approx scale Increased soil sampling intensity generates a more accurate soil test map, but cost increases with finer scale. 0.5 ac grid 1.1 ac grid 2.5 ac grid 4.4 ac grid 5 Zone Field $ $$$$ What are the economics of soil sampling Intensity? Field Composite

26 Assessing Spatial Sampling Intensity Sampled April Acres Split Field into 2 Comp Samples Grid Sampled 1.1 Acre grids 2.5 Acre Grids 4.4 Acre Grids 6 Zone Sample Areas Field 155 acres South East Nebraska Corn/Soybean Rotation 9/13/2017

27 Soil Sampling Programs Sample Size Comp # Acres # of Samples # of Cores Cost Cost per Field Cost per Acre $55/sample $55 $.71 Comp # ac $55/sample $55 $ Acre Grid $22.40/acre $3517 $ Acre Grid $10.50/acre $1658 $ Acre Grid $8.00/acre $1240 $ Zone 6 60 $93/zone $558 $

28 Soil Test Ranges ph P K Min Max Avg Min Max Avg Min Max Avg Grid Grid Grid Comp # Comp # Zone Zone Zone Zone Zone Zone

29 Basis for Fertilizer & Lime Application 2 year Program 150 bu/ac Corn & bu/ac Soybeans ph ph Raise Raise to 6.5 to 6.5 depth depth of 6 inches of 6 inches P Build P Build to 25 to PPM 25 PPM Removal Removal to 35 to PPM 35 PPM K Build K Build to 200 to PPM 200 PPM Removal Removal to 225 to 225 N 1.1 X YG 35lbs SB Credit N in P & S N 1.1 X YG 35 lbs/ac SB Credit N in P & S S 16 PPM * Zn S 1.0 PPM 16 PPM * * Zn 1.0 PPM * *Producer choose yield goals, P, S & Zn levels * Producer choose yield goals, P, S & Zn levels 29

30 Fertilizer & Lime Material Cost per Ton Nitrogen: $ Phosphorus: $ Potassium: $ Sulfur: $ Zinc: Zn Sulfate 35% $ 1.30/ lb Ag Lime: Application based on 100% ECCE, lime used in formulas is 1,500 ECCE corrected to 100% $

31 Total Field Nutrient Requirements in Tons (155 acres) Ag Lime MAP K S Zn 32% Grid ac Grid ac Grid ac Comp - # Comp - # Total Comp Zones

32 Field Total Nutrient & Sample Cost by Sample Method Ag Lime 100% ECCE Map K S ZN 32% Sample Cost/Field Total Cost Cost/Acre Grid-1.1 $11,760 $6,171 $1,187 $732 $884 $7040 $3,517 $31,291 $202 Grid-2.5 $10,008 $6,101 $160 $524 $650 $7,020 $1,658 $26,121 $168 Grid-4.4 $11,424 $3,699 $37 $888 $156 $7,462 $1,240 $24,906 $161 Comp #1 and #2 $16,721 $7,925 $0 $1864 $0 $6,591 $110 $33,211 $214 Zones $16,842 $7,111 $0 $440 $624 $6,854 $558 $32,429 $ acre vs Zone Map Field Savings $

33 The Value of Grid Sampling Grid sampling cost $9.99 per acre more than a single composite sample, but reduced lime + fertilizer cost $55.08 per acre. A total savings of $44.38 per acre, or $6,789 for the field. Soil Sampling Strategy Cost $/ac 2.5 ac Grid (155 ac) $10.70 Lime + P and K $ Whole Field (155 ac) $0.71 Lime + P and K $ Soil sample cost: sample collection + lab analysis (ph, P, K, CEC, SOM and micros). Lime cost $42.00, P $470.00/ton and K $340.00/ton.

34 Cost of Soil Testing Soil Testing is the least expensive production item and impacts cost of lime and nutrients. Thus grid soil testing is one of the most cost effective tools, optimizing lime and fertilizer application to where greatest potential of crop response. Production Item 1 Cost $/ac Seed Corn (36,000 sds/ac) Seed Beans (140,000 sds/ac) Pesticide (two applications) Nitrogen (appl lbs/ac) Soil Test (2.5 ac grid 4yr) Soil Test (1.1 ac grid 4 yr) Seed costs based on University and grower observations, pesticide expenses Gary Schnitkey, University of Illinois, urea nitrogen $425/ton + application. 2 Soil Test based on collection of sample and Laboratory analysis (ph, P, K, SOM and micros) amortized over 4 years. Miller and Czyryca, 2018

35 Soil Laboratory Analysis Indiana growers submit 600, ,000 soil samples yearly for nutrient management. What steps are taken to insure quality of lab results? Internal labs employee quality control (QC) procedures reference checks, dups and blanks. Externally labs can be certified through the Illinois Soil Testing Association (ISTA-LAP). Performance evaluated three times per year. Miller and Lindaman, 2018

36 ISTA Lab Certification Program Data from the ALP soil proficiency program is evaluated for 26 participating Midwest labs. ISTA-LAP assessor 1 evaluates lab performance 2, ph " 0.2, and P and K " 15% on five soils. Certification requires passing score for each method. Certified labs posted at ISTA web site: ww.soiltesting.org/certified_labs 2 Lab performance certification criteria can be found at the ISTA web site. Proficiency Soils 3 cycles/yr ISTA-LAP Assessment ISTA Web site Listing 1 Mike Lindaman, ISTA Assessor Miller and Lindaman, 2018

37 ISTA-LAP Certified1 Labs 2018 A & L Great Lakes Laboratories, IN AgSource Cooperative Services, WI Black Log Ag Services, IL Charter Soil Service, IL GMS Laboratories, IL Ingram s Soil Testing, IL KSI Laboratory, IL Midwest Laboratories, NE Rock River Laboratory, WI SGS Laboratory - Toulon, IL Solum Laboratory Winfield, IA Southern Illinois Ag Solutions, IL Spectrum Analytic, OH 1 Sure-Tech Labs, IN United Soils Inc., IL Waters Laboratory, KY Way Point Analytical Atlantic, IA Way Point Analytical Champaign, IL Way Point Analytical Lab Memphis, TN Certified labs posted 3 May, Sept, and Jan. at ISTA web site. Certification list updated: Sept. 2018, Next update Jan Miller and Lindaman, Miller,

38 ISTA LAP Program Labs Pending Certification AgroLab, DE AgSource, IA Black Log Services, IL Logan Labs, OH Pro-Ag Consulting, IL The Farm Clinic, IN Non-Certified Labs 2018 Agri-Labs, Auburn, MI Calmar Soil Testing, Westerville, OH CLC Labs, Westerville, OH Litchfield Analytical, Litchfield, MI MSU Soil Lab, Lansing, MI Star Lab - OARDC/OSU, Wooster, OH Reasons for not participating: Cost of program, additional lab work, not that important. Miller and Lindaman, 2018

39 Closing Observations Soil samples per grid point: 8-12 cores. Soil Test variability (RSD): STP > Soil NO 3 -N > STK > SOM > ph. STP variability: No Till > Min Till > Conventional. Economics show grid sampling is effective, especially with regard to variable rate lime application. Soil Testing is low cost per acre, < $3/ac Select a Certified Soil Testing Lab:

40 Acknowledgements David Taylor, Harvest Land Co-op, IN Steve Dlugosz, Harvest Land Coop, IN Craig Struve, Soil View, IA Chris Nelson, Soil View, IA Kess Berg, A&L Great Lakes, IN Tim Smith, Cropsmith,IL Bill Urbanowisz, Spectrum Analytical, OH John Grandin, Riverland FS, IL Mike Lindaman, LGI Laboratory, IA Richard Finstead, Frontier Labs, IA Greg Ikins, United Soils Lab, IL

41 You can not manage what you can not measure. Tom McGraw, Midwest Independent Soil Samplers If you don t manage your sampling what can you measure? - R. Miller, Colorado State University (ALP)

42 Thank you for your time and attention