UMBS DIRT Soil Properties & pH
Written by John Den Uyl (2/22/2018)

This file contains soil pH measurements taken by Jim LeMoine in October of 2004 (year 0 of the DIRT project at UMBS) and in 2014 (year 10 of the DIRT project at UMBS) for each DIRT treatment, including maximum pH, minimum pH, mean pH, and standard deviation calculated for 3 sampling depths (Oea/A, 0-10cm (2004 only), 10-20cm (2004 only)). 3 individual soil samples were taken at each plot at each of the 3 sampling depths, and there are 3 plots (1 plot per experimental block) per treatment, providing 9 pH samples for each sampling depth in which the following values were calculated.

The "UMBS_DIRT_pH_by_Treatment_by_Depth_2004.csv" and "UMBS_DIRT_pH_by_Treatment_by_Depth_2014.csv" files include pH measurements arranged by treatment and sampling depth for the corresponding years.

DIRT Site Soil Properties
The DIRT plots at UMBS are located on a well-drained, sandy Spodosol soil (Rubicon series). A and upper B horizons are 92% sand, 5% silt by mass. O horizons are generally poorly defined, and sampling techniques combine the Oe, Oa, and upper A horizon as the organic layer (Oea/A). There are almost no rocks or large stones. Leaf litterfall averages around 1200kg C/ha/yr.

Method for Determining Soil pH
Written by Pat Micks (April 14, 2006)
Personnel involved: Jim LeMoine, Pat Micks

Adapted from SSSA Methods
Note: The method in SSSA uses 1:1 ratio of liquid to soil. For the UMBS DIRT soils, we used a 2:1 ratio.

From: Methods of Soil Analysis. Part 3: Chemical Methods. 1996. Published by Soil Science Society of America, Inc., and American Society of Agronomy, Inc. Madison, WI, USA

Reference: Peech, M. 1965. Hydrogen-ion activity. P. 914-926 in C.A. Black (ed.) Methods of soil analysis. Part 2. Agron. Monogr. 9. American Society of Agronomy and Soil Science Society of America, Madison, WI.

Reagents:
0.01 M CaCl2
pH 7 and 4 buffer solutions

Procedure:
1. Calibrated pH meter
2. Weighed 10 g of air-dry soil into scint vial
3. Added 0.01 M CaCl2 solution to soil in the ratio 2:1 (ml solution: g soil) and mixed well with stirring rod
4. Let samples stand for 10 minutes
5. Stirred the suspension and placed electrode in the supernatant (liquid above the settled soil)
6. Recorded pH to 0.01 units
7. Rinsed electrode with DI water between samples

Method for Soil Sampling
Written by Jim LeMoine (November 2004)
Personnel involved: Jim LeMoine, Pat Micks, Knute Nadelhoffer

Samples were collected directly beneath the 3 respiration collars in each plot. We collected 3 Organic/A ‘brownies’, 3 0-10 cm mineral, and 3 10-20 cm mineral samples from each of the 27 plots.

Organic/A: The respiration collar was carefully removed and recent litter and still-recognizable Oe material were brushed away. Using a sharp knife, a spatula, and a 14 cm x 14 cm template we cut and collected a ‘brownie’ consisting of the remainder of the Oe material, the Oa material, and the A horizon soil. For most samples the uppermost mineral soil was a mixture of grey and dark brown material, grading to all grey with depth. In order to capture the A horizon we collected all of the grey-brown mixture in locations where this layer was thin. In other cases where this layer was very deep, changing color gradually to all gray, we did not collect all of it but rather kept the brownie to no more than about 6 cm depth. If we sampled too deeply we scraped the gray soil off of the bottom of the brownie and let it fall back into the sample hole. After the brownie was removed and placed in a ziploc bag, we patted the mineral soil evenly over the bottom of the hole and recorded the depth of the hole on each of 4 sides (1 measurement per side) to the nearest half-centimeter.

We have removed all recognizable fragments from the O layer but are still calling it Oea/A

Mineral: We used a 30 cm AMS stainless steel split corer with a slide hammer to collect the mineral samples from the same locations as the brownies were taken. Three 10 cm clear plastic sleeves were placed in the core body. The corer was driven 20 cm into the soil, starting at the exposed mineral soil surface at the bottom of the brownie hole. The soil was moderately moist and held together well in the sampler. After the corer was opened, the 0-10 and 10-20 cm sections were separated slightly and the boundary between them cut with a knife. The two samples were bagged separately in ziploc bags. This procedure was followed for each of the three sampling locations in each plot.