Soil Analysis

Soil testing is an important tool for fertility evaluation. We offer three types for services:

  • Standard soil fertility test package
  • Nitrogen testing
  • Research soil testing

Standard soil fertility test package:

Under our extension services we offer standard soil fertility test packages. Beginning Fall 2014 the SPAL will be offering a new test service “Moist Soil Sample Analysis” for both research and grower communities for the determination of Mehlich 3 extracted potassium and phosphorus in as-received moist samples. Recent research has indicated that the soil test potassium values from a moist sample analysis correlates better with yield response for corn and soybean.

In our dry soil sample analysis package, oven dried samples are tested for Mehlich3 phosphorus (Olsen P is performed for samples with pH greater than 7.3) and potassium, pH and Sikora buffer pH for lime requirement. Organic matter, ammonium acetate calcium, magnesium and sodium, and DTPA extractable zinc can be added to the standard soil fertility test packages for additional charge. The lab will offer interpretations of potassium and phosphorous and fertilizer recommendations for both dried and moist soil samples.

Other special tests (inorganic nitrate and ammonium nitrogen, hot water boron, total carbon and nitrogen, DTPA extracted Fe, Cu, and Mn, soluble salts, and total elements such as P, K, Na, Ca, Mg, Mn, Al, B, Fe, Zn, Cu, Fe, S, Pb, Si, As, Cd, Be, Cr, etc.) can be requested from our research testing services.

For Field (Agronomic) crops:
  • Field crops Standard Fertility Test Package
  • Includes Mehlich3 potassium, phosphorous (colorimetric), pH and lime. Organic matter and DTPA zinc can be added as additional tests.
  • Informational Sheets for field and vegetable crops
  • For Horticultural crops, Lawn and turf:
  • Horticultural Crops Standard Fertility test Package
  • Includes ammonium acetate potassium, Bray1 phosphorous (colorimetric), pH and lime. Organic matter, ammonium acetate extracted magnesium and calcium and DTPA zinc can be added as additional tests.
  • Informational Sheets for tree fruits and grapes
  • Nitrogen testing:

    The late-spring test for soil nitrate enables site-specific assessments of plant-available N just before the crop begins rapid uptake of N. This test will allow corn producers to manage N applications to increase their profits while reducing environmental degradation. Late season nitrate test:

  • Late spring soil nitrate test for corn
  • Research soil testing:

    The research soil testing services provides flexibility to researchers to select specific elements of interest when requesting analyses. Any individual test from the standard fertility test package can also be requested under our research service. The research tests include: 2M KCl extracted inorganic nitrate and ammonium nitrogen; hot water boron; total carbon and nitrogen; ammonium acetate extracted K, Ca, Mg, and Na; Mehlich3 extracted P, K, Ca, Mg, Na, Fe, Al, Mn, Cu, and Zn; DTPA extracted Fe, Cu, and Mn; soluble salts; and total elements such as P, K, Na, Ca, Mg, Mn, Al, B, Fe, Zn, Cu, Fe, S, Pb, Si, As, Cd, Be, Cr, etc.

    Special rates are available for prepared samples on most tests. Rush rate is available at 50% surcharge above regular rate. Please contact the lab for additional details.

  • Soil research form (Other special tests)
  • Moist Soil research form (New)
  • ‘Do-it-yourself’ option for sample analysis is available to ISU researchers.

  • 'Do-it-yourself' sample submission form.
  • Additional Resources