3
SAMPLING OF SOIL, GRASS AND SHEEP BONE
The analytical methods and counting techniques are lengthy and complicated so that the
number of samples that can be analyzed in a year is limited. The sampling procedure had to be
designed with the utmost economy of numbers, but it was decided nevertheless to include in the
survey a wide range of climate and soil conditions. Soil and grass samples were confined to
permanent grassland, so as to avoid the alterations in the soil activity profile brought about by
cultivation.
1000 |
x
x
400 -—
x
—
G
x
>
of
ao
§& 10F—
xx
9
a
ay
_
x
a
0
x
a
¥
oO.
—
|
{
x
|
10
puc/G Ca BY NHe Ac
100
1000
Fig. 3—Comparison of Sr®*°/Ca ratios in soil by HCl and NH,Ac extraction.
A list of sampling stations in use in 1956 is given in Table 1.
Stations A to G are farms carrying sheep on permanent pasture, A to E are hill farms, and
F and G are lowland farms. One half-acre plot was selected for sampling on each station, except Station A, where two such plots were chosen. The plots were intended to be typical but not
fully representative of the grazing, which on hill farms varies greatly from place to place.
Soil cores were taken in July 1956, from 10 or 12 points on each plot to a depth of 4 in. and
a square yard of herbage surrounding each soil core was cut as closely as possible with shears.
The sites had been grazed up to a few weeks before sampling, and the growth was therefore
fresh. The soil and herbage sub-samples were bulked and mixed before analysis. Leg bones
from a sheep between 12 and 15 months old, which had grazed pasture similar to and including
the sampling plot for at least several months previously, were taken at each station. Yearlings
were stipulated to ensure recent but mature bone growth.
To supplement the sheep stations, soil and grass were taken at five auxiliary stations. One
of these (A3) is in the Cwmystwyth Valley, at Pwllpeiran, about 5 miles from the stations Al and
A2. The sampling area at A3 is in an upland valley, and is typical of the pastures to which the
sheep are brought down in bad weather. The other four stations (H to K) are on former airfields, all within 15 miles of Harwell, and having similar meteorological but dissimilar soil
Status. At these auxiliary stations, small plots of about 20 sq yd were fenced off. The soil cores
and the herbage were taken from within these enclosed plots. At each of stations H to K in July,
1956, three cores were taken to depths 12 in., and divided into three horizons of 4 in. each to
212
per acttgye: