Standard Soil Lab Data Reports

•Soil sampling strategies have evolved over the past 100 years since USDA first was charged with the mapping, sampling, and analysis of soils.

•Today, National Soil Survey Center is located in Lincoln NE, and soil samples collected by Soil Surveyors are sent there for analysis.

•Most soils studied are submitted for “Soil Characterization” analyses

–A series of physical and chemical analyses

–Very elaborate, but also somewhat geared toward applications to agriculture

–Usually does not include total chemical analyses, but instead a number of easily extractable components

• Available soil data is on web. Can be accessed by

–Location (state and county)

–Soil name (if you already know the series name)

Accessing Data on the Web

Munsell colorstructure

consistencetexture

Horizons

A1

A2

A3

A4

Bt

Bqm1

Bqm2

Bqm3

C

•Soil series = san joaquin

•Soil classifcation will be discussed later

•Methods are listed for every data type. Methods can be traced back to USDA lab manual

•Sand silt and clay are given, as well as further breakdowns of each

•Gravel is given (and breakdown of gravels)

Particle size row

•Dithionite removes Fe oxides

•Ratio to clay is CEC/g clay and water holding cap/g clay

•Bulk density at 2 water contents

•Water retention (cm water per cm soil)

Chemistry row

Extractable bases are those removed from clay via ammonium acetate.

Note that sum of bases removed may commonly exceed CEC

Extractable bases are those removed from clay via ammonium acetate.

Note that sum of bases removed may commonly exceed CEC

Electrical conductivity is a measure of total dissolved salts.

EC is a measure of salt influence on water uptake via solute potential in water

0-2 = non saline

2-4 = salt sensitive

>4 = saline

Some additional analyses not in San Joaquin example

Chemistry of saturation extract (or 1:1 extract)

- chemistry of water in equilibrium with soil

- reflects plant available water

- usually only in arid environments

Mineralogy

- can be found on separate data forms sometimes

Total Chemistry

- rarely done, but sometimes available

Typical Calculations Using Soil Data

•Total of something to a given depth

–You have already done this

•Average property for whole soil or to some depth

–Wieghted mean approach………

Weighted Mean for a Common Problem

Determine the mean N content of a soil to 50 cm

1. Determine total mass and total N in each horizon

2. Sum up both to depth of 50 cm (make sure if last horizon goes beyond 50 cm, reduce its total thickness).

3. Divide total N by total soil mass.

Weighted mean by horizon thickness (assumes BD same in all horizons).

1. Mean = [(thickness)1(N%)1+all horizons]/50 cm