KBS032: LTER Biodiversity Experiment Baseline Soil Sampling Protocol
In use from 2000-01-01
Abstract
Sample collection and processing protocol for the LTER Biodiversity plots.
Protocol
Sample Collection and Processing
The LTER Biodiversity plots are 9.1 × 27.4 m (30 × 90 feet). Soil
cores are collected at each of two sampling stations along a transect
that is centered between the east and west sides the plot. One
sampling station is 9 meters from the south border of the plot on the
west side of the transect, the second station is 18 meters from the
south border of the plot on the east side of the transect. The cores
are taken in at area of approximately 0.5 × 0.5 meters. Half of the
cores are taken within the crop row and half are taken between the
rows. Distances to sampling stations are estimated by pacing.
A total of six 0-25 cm cores (three at each station) are collected and
composited. A second set cores, from 0-10 cm in depth, are collected
at the two sampling stations, two cores at each station, and
composited. Before sampling each plot, a core is taken at the edge of
the plot and discarded to prevent carryover between plots. Latex
gloves are worn when collecting soil cores in the field and while
sieving. Soil samples are sieved using a 4 mm mesh sieve.
Soil samples are refrigerated at 4C until processing is complete.
Ideally, samples for inorganic nitrogen and soil moisture should be
processed within 24 hours of collection. The maximum time between
collection and processing is 48 hours. Archive samples to be used for
microbial (e.g. Phospholipid Fatty Acids) or DNA analysis should be
frozen at -80C within 48 hours of collection.
The 0-25 cm soil sample is analyzed for inorganic nitrogen (NO3 and
NH4 pools) and soil moisture. The remainder of the sample is air
dried and archived. The 0-10 cm soil cores are archived. Four
whirlpaks containing 25-30 g each are frozen at -80C and the remainder
is air dried and archived.
Inorganic Nitrogen
Weigh 10 ±0.01 g of sieved soil into a
urinalysis cup (u-cup). Add 100 ml of 1 M KCl, shake for one minute
and allow to stand overnight. Shake again for one minute the next day
and let stand for about one hour or until the supernatant partially
clears. Filter the supernatant with a syringe filter using a type A/E
1 µm pore size glass fiber filter. Refrigerate filtered supernatant
if analysis will be done within one week, otherwise freeze extract at
-10C to hold for analysis. Analysis for inorganic nitrogen is
performed on an Alpkem segmented flow analyzer.
Moisture
All weights for soil moisture are measured to
nearest 0.01 g. Label a soil tin with sample ID. Record weight of
“Tin, Lid, and Label”. Place 20-25 g of sieved, field moist
soil in the tin. Weigh and record the weight of the fresh soil. Dry
open tins in an oven at 105C for at least 24 hours. Remove from the
oven and place lid on tin. When cooled to room temperature, record
weight of “Tin, Lid, Label, and Dry Soil”. The weight of the
dry soil is calculated by subtracting the “Tin, Lid, and Label”
weight from the “Tin, Lid, Label, and Dry Soil” weight. Soil
moisture is expressed on a % dry weight basis by the formula: % Soil
Moisture = 100 * [(Fresh weight – dry weight)/dry weight]
Author: Tim Bergsma
Edit | Back