Soils were sampled from the long-term NPP plots. At 14 of 15 sites a
grid of 70 by 70 meters was laid out. Within this, 49 plots of 10 by
10 meters were placed and labeled (numbered) in serpentine design. At
the 15th site, P-Coll, 48 plots of 10 by 10 meters were laid out in
three long rows of 16 plots per row. At all sites the soil sample of
0-10 cm depth was taken 1 meter from the NE marker bar at a diagonal
(heading toward the SW marker). At one of each of the five vegetation
types another set of 49 soils (#101-149) was taken from within one of
the 10 by 10 meter plots. Using a 7 by 7 meter grid (bounded by the
southern east-west boundary line and the western north-south boundary
line [#149 is in the SW corner]) soils were sampled 1 meter apart
using a serpentine design.
Storage
: Soils were kept in plastic bags and
stored in a partly cooled house trailer in New Mexico over a two week
period.
%
H2O
--Soil subsamples were
taken from the plastic bags, placed in soil cans and dried at 105C for
two days. The difference in mass before and after drying was used to
estimate water content. soil gravimetric moisture = (fresh weight –
dry weight) / dry weight
Saturation %--
Soils were air dried and seived to
2mm. One hundred grams of soil was weighed into a disposable drinking
cup. Using a 250 ml buret, water was added. The soil was stirred to
take up the water, which was added until saturation was attained. The
amount of water required was recorded. Saturation %= (mls water/ wt of
soil) X 100. One * or two * * in column next to sat% indicates sample
was a little too wet and too wet, respectively. It may be necessary to
subtract 0.5 ml and 1.0 ml from the amount of water. See references
for description of what saturation looks/is like in different soils.
References: Rhoades, J.D., 1982. Soluble Salts. in A.L. Page(ed.).
Methods of Soil Analysis Part 2- Chemical and Microbiological
Properties.
Soil pH
--2:1 To ten grams of 2mm seived soil, 20
mls of RO (reverse osmosis-purified) water was added. It was stirred
and left to sit for 10 min. The pH was read on the liquid above the
soil.
Soil TKN
-One gram (0.5 g for PS and PC) of 2 mm
seived air-dried soil was digested using microkjeldahl method with 40
tube heating block. A mercury-potassium sulfate catalyst was used. The
digest went for two hours after clearing at 375 C. Digests were
analyzed colorimetrically on a Technicon autoanalyzer. Reference:
Bremner, J.M., and C.S. Mulvaney. 1982. Nitrogen--Total. In A.L. Page
(ed.). Methods of soil analysis. Chemical and microbiological
properties. Agronomy 9 (2):595-694. Am. Soc. of Agron., Madison, Wis.
