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Several state universities and other organizations have carried out blind comparisons of soil analysis results and the resulting fertilizer recommendations provided by laboratories operating in the area. The objective was to compare the way different laboratories interpret how much fertilizer to apply at a given soil test level and the effect on production costs.
Following is a summary of publically available comparisons which included the Servi-Tech Laboratory. Note that some of the laboratories are no longer in business.
The fertilizer costs quoted for each study were supplied by the authors of the respective reports. All yields, costs, and returns are averaged over the length of the study.
Several state universities and other organizations have carried out blind comparisons of soil analysis results and the resulting fertilizer recommendations provided by laboratories operating in the area. The objective was to compare the way different laboratories interpret how much fertilizer to apply at a given soil test level and the effect on production costs.
Following is a summary of publically available comparisons which included the Servi-Tech Laboratory. Note that some of the laboratories are no longer in business.
The fertilizer costs quoted for each study were supplied by the authors of the respective reports. All yields, costs, and returns are averaged over the length of the study.
The "return over fertilizer investment" is calculated by subtracting the check yield (no fertilizer applied) from the yield reported for each laboratory treatment.
This furnishes the extra corn yield and the resulting increase in gross income that was produced by using the fertilizer recommendations generated by each laboratory.
The individual fertilizer costs for each laboratory's recommendations are then subtracted from the increased gross income. The result is the return over the fertilizer investment "in dollars per acre". The “fertilizer cost per bushel produced” was calculated if there was no unfertilized check included in the particular study.
¶ Table 1. Weld County, Colorado, 2001, Single-Year |
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|---|---|---|---|
| Laboratory Name | Corn Yield, bu/ac | Fertilizer Cost, $/ac | Fertilizer Cost, ¢/bu |
| ServiTech, Dodge City KS | 255 | $56.52 | 22.2 ¢ |
| Colorado State Univ., Ft. Collins CO | 245 | $47.88 | 19.5 ¢ |
| Olsen’s Lab, McCook NE | 254 | $46.09 | 18.1 ¢ |
| Weld Labs, Greeley CO | 247 | $63.96 | 25.9 ¢ |
| Western Labs, Parma ID | 253 | $130.02 | 51.4 ¢ |
| Midwest Lab, Omaha NE | 248 | $57.24 | 23.1 ¢ |
| Field-length strip plots were established in 2001 as part of Colorado Corn Growers Assn. demonstration on furrow-irrigated Julesburg sandy loam and One fine sandy loam. | |||
¶ Table 2. Rock County, Nebraska, 1987–1990, Four-Year Averages |
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|---|---|---|---|
| Laboratory Name | Corn Yield, bu/ac | Fertilizer Cost, $/ac | Fertilizer Cost $/bu |
| ServiTech, Dodge City KS | 159 | $54.00 | $0.340 |
| Univ. of Nebraska, Lincoln NE | 162 | $48.00 | $0.300 |
| Harris Labs, Lincoln NE | 159 | $94.00 | $0.591 |
| A&L (Midwest) Labs, Omaha NE | 161 | $85.00 | $0.528 |
| These plots were established in 1987 under center pivot irrigation at the B-K-R demonstration farm near Bassett, NE. The soils consist of approximately two feet of sandy loam to loamy sand that overlays coarse sand and gravel. Each laboratory was given a yield goal of 165 bushels of corn per acre. | |||
¶ Table 3. Weld County, Colorado, 20010, Single-Year |
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|---|---|---|---|
| Laboratory Name | Corn Yield, bu/ac | Fertilizer Cost, $/ac | Fertilizer Cost, ¢/bu |
| ServiTech, Dodge City KS | 191 | $50.39 | 26.4 ¢ |
| Colorado State Univ., Ft. Collins CO | 191 | $55.54 | 21.1 ¢ |
| Stukenholtz Lab, Twin Falls ID* | NA | $121.35 | 63.5 ¢ |
| Weld Labs, Greeley CO | 193 | $68.50 | 35.5 ¢ |
| Western Labs, Parma ID | 190 | $54.88 | 28.9 ¢ |
| Midwest Lab, Omaha NE | 190 | $71.00 | 37.4 ¢ |
| *Yield results were unreliable due to water and compaction problems. Per bushel cost calculated using average yield of 191 bushels. Field-length strip plots were established in 2000 as part of Colorado Corn Growers Assn. demonstration on furrow- irrigated Vona sandy loam/loamy sand. |
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¶ Table 4. Larimer County, Colorado, 1984–1987, Four-Year Averages |
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|---|---|---|---|
| Laboratory Name | Corn Yield, bu/ac | Fertilizer Cost, $/ac | Return over Fertilizer $/ac |
| ServiTech, Dodge City KS | 151 | $46.75 | $118.55 |
| Colorado State Univ., Ft. Collins CO | 151 | $53.25 | $112.05 |
| Harris Labs, Lincoln NE | 145 | $71.75 | $76.15 |
| A&L (Midwest) Labs, Omaha NE | 153 | $63.75 | $107.35 |
| Inter-American Labs, Cozad NE | 150 | $72.25 | $90.15 |
| Triple "S" Testing, Loveland CO | 151 | $66.76 | $98.55 |
| Unfertilized check | 94 | --- | --- |
| These plots were established in 1984 at the Colorado State University Agronomy farm near Ft. Collins, Colorado, on a Nunn clay loam. Each laboratory was given a yield goal of 175 bushels of irrigated corn per acre. | |||
¶ Table 5. Merrick County, Nebraska, 1982–1984, Three–Year Averages |
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|---|---|---|---|
| Laboratory Name | Corn Yield, bu/ac | Fertilizer Cost, $/ac | Return over Fertilizer $/ac |
| ServiTech, Dodge City KS | 136 | $41.45 | $33.95 |
| Univ. of Nebraska, Lincoln NE | 131 | $24.92 | $35.98 |
| Harris Labs, Lincoln NE | 130 | $71.34 | $-13.34 |
| A&L (Midwest) Labs, Omaha NE | 136 | $56.27 | $19.13 |
| Inter-American Labs, Cozad NE | 131 | $80.95 | $-20.05 |
| Unfertilized check | 110 | --- | --- |
| These plots were established in 1982 on a deep sandy loam soil. Each laboratory was given a yield goal of 200 bushels of irrigated corn per acre. | |||
¶ Table 6. Clay County, South Dakota, 1981–1985, Five–Year Averages |
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|---|---|---|---|
| Laboratory Name | Corn Yield, bu/ac | Fertilizer Cost, $/ac | Return over Fertilizer $/ac |
| ServiTech, Dodge City KS | 102 | $31.33 | $52.77 |
| South Dakota State Univ., Brookings SC | 101 | $28.68 | $52.52 |
| Iowa State Univ., Ames IA | 101 | $44.96 | $36.24 |
| Harris Labs, Lincoln NE | 98 | $55.76 | $16.74 |
| A&L (Midwest) Labs, Omaha NE | 100 | $59.15 | $19.15 |
| Unfertilized check | 73 | --- | --- |
| These plots were established in 1981 at the Southeast Experiment farm, near Beresford, South Dakota, on an Egan silty clay loam, a well drained soil formed in silty drift over glacial till. Each laboratory was given a yield goal of 120 bushels of corn per acre. | |||
¶ Table 7. Phelps County, Nebraska, 1982–1984, Three–Year Averages |
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|---|---|---|---|
| Laboratory Name | Corn Yield, bu/ac | Fertilizer Cost, $/ac | Return over Fertilizer $/ac |
| ServiTech, Dodge City KS | 127 | $34.37 | $287.53 |
| Univ. of Nebraska, Lincoln NE | 121 | $25.25 | $279.25 |
| Harris Labs, Lincoln NE | 119 | $59.74 | $238.96 |
| A&L (Midwest) Labs, Omaha NE | 125 | $66.05 | $250.05 |
| Inter-American Labs, Cozad NE | 125 | $54.63 | $261.47 |
| Unfertilized check | 16 | --- | --- |
| These plots were established in 1982 on a Holdrege silt loam that had been recently graded for gravity irrigation so that nearly all the topsoil was removed. Each laboratory was given a yield goal of 170 bushels of irrigated corn per acre. | |||
¶ Table 8. Shawnee County, Kansas, 1980–1983, Four–Year Averages |
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|---|---|---|---|
| Laboratory Name | Corn Yield, bu/ac | Fertilizer Cost, $/ac | Return over Fertilizer $/ac |
| ServiTech, Dodge City KS | 139 | $41.24 | $153.06 |
| Kansas State Univ., Manhattan KS | 140 | $27.57 | $169.63 |
| Harris Labs, Lincoln NE | 140 | $57.53 | $139.67 |
| A&L (Midwest) Labs, Omaha NE | 125 | $64.57 | $89.13 |
| Unfertilized check | 72 | --- | --- |
| These plots were established in 1980 at the Kansas River Valley Experiment Field near Rossville, Kansas. Apparently only one soil sample was collected at the beginning of the study and the resulting fertilizer recommendations were repeated annually for the duration of the study. | |||
Hergert, G.W., D. Bauer, and B. Stolzenburg. 1990. Soil test lab comparison experiment on the BKR Demonstration Farm. Soil Science Research Rept. - 1990. Dept. of Agronomy, Univ. of Nebraska, Lincoln, Nebr. pp. 79-83.
Follet, R.H. and D.G. Westfall. 1988. Fertilizer recommendation comparison study. Tech. Rept. TR88-5. Dept. of Agronomy, Colorado State Univ., Fort Collins, Colo. 8 pg.
Gelderman, R., J. Gerwig, P. Fixen, B. Farber, B. Lawrensen, and D. Dubois. "A comparison of several soil testing laboratory fertilizer recommendations". Southeast South Dakota Experiment Farm - Progress Report. pp. 48-51. Agri. Expt. Station, South Dakota State Univ. 1985.
Olson, R.A., P.H. Grabouski, F.N. Anderson, K. Frank, and C.A. Shapiro. "Soil test comparison results for 1984". Soil Science Research Report. Section 25. Dept. of Agronomy. University of Nebraska. 1984
Soil Fertility Staff, Dept. of Agronomy. "A comparison of suggested fertilizer programs obtained from several soil test laboratory services". Agronomy Dept. Report No. 49. IANR, Univ. of Nebraska. 1985.
Whitney, D.A. "Comparison of fertilizer recommendations made by several laboratories". 9 pages. Agronomy Dept. Kansas State Univ. 1986.
Bauder, T. Choosing a Soil Testing Laboratory. CSU Demonstration Site Results, Colorado Corn Growers Assn.