2002-07-08_GENERAL DOCUMENTS - M2002004 ‎(4)‎

• Permit No: M2002004
• IBM Index Class Name: GENERAL DOCUMENTS
• Doc Date: 7/8/2002
• Doc Name: ATTACHMENT, PART 3
• From: HABITAT MGMT
• To: DRMS
• Media Type: D
• Archive: No

and the dilution effect on any spoil toxicant as soil
depth increased would favor a linear response. Actual
forage production for this situation was substantially
less than that for other spoil types. Plots utilizing acid
spoil were located in the relatively arid southwestern
corner of the NGP. In this region, forage production of
approximately 85 g m-2 was considered indicative of
good range conditions in average years, and a soil depth
of 97 cm over acid spoil was required to obtain this pro-
duction.
Patterns of moisture withdrawal for acid spoil were
similar to those presented in Fig. 3 for generic spoil. In-
formation from coring demonstrated that plant roots
did not penetrate into spoil overlain with soil, and a root
mass was found 5 to 10 cm above the soil /spoil inter-
face.
The exact cause of the linear response of grass pro-
duction to increasing soil depth over acid spoil has yet to
be identified. But regardless of the causal agents, the
management implication is that strongly acid spoil
should be neutralized prior to soil application or that
such spoil should be buried by higher pH material be-
fore applying soil.
Soil -Like Spoil
This spoil type was mildly alkaline, low in soluble
salts, carbonaceous material, and heavy metals, and silt
loam in texture (Table I) with montmorillonite domi-
nating the clay fraction. Plant establishment in spoil
was relatively high when compared with that measured
in soil. One plot, located in Wyoming, contained soil -
like spoil.
Forage production as a function of soil depth is pre-
sented in Fig. 2. The highest relative production (80
of the maximum yield) was measured when spoil com-
posed the entire growth medium. Production showed an
irregular pattern of increase and decrease throughout
the plot and was unrelated to soil depth. Rodent damage
and vagaries in plant establishment were two of the
more obvious factors causing yield variations.
Patterns of moisture withdrawal departed from the
generic situation presented in Fig. 3. Significant mois-
ture withdrawal was observed throughout the 110 -cm
monitoring zone in both soil and spoil, and there was no
indication of roots concentrating at the soil /spoil inter-
face.
Precise identification of the chemical and physical
traits that made this spoil conducive to plant growth was
not possible. The soil -like spoil used in this plot was ob-
tained from overburden lying near the surface (within
the upper 20% of the highwall). This material was pre-
sumably weathered under existing environmental condi-
tions, a situation not thought to exist with the other
spoil types. The spoil contained relatively low levels of
Fe and other minerals; high mineral levels can interfere
with plant nutrient absorption. In addition, the spoil
was essentially free of carbonaceous material, a con-
stituent of other spoil types that appeared detrimental to
plant growth. Working with spoil in the midwest,
McFee et al. (1981) were likewise unable to precisely de-
fine spoil properties adversely affecting plant growth.
so-
80-
70-
60-
50-
40-
30 -
20-
10-
0
90 -
50 -
70 -
60-
50-
40-
30-
20-
10-
0
60
70
60
50
40
30
• NATIVE GRASSES
o INTROWR D GRASSES
• WET (MOWING SEASON
°DRY GROWNG SEASON
20
to
125 150
25 50 75
DEPTH OF SOIL OVER SPOIL, CM
Fig. 4— Response of cool- season grass production to increasing sell
depth over spoil (spoil types combined) on the basis of species
origin, precipitation, and time.
Influence of Species, Precipitation, and Time
The production data were also pooled on the basis of
species, precipitation, and years to evaluate the
influence of these variables on soil depth requiremnts.
Results are presented in Fig. 4.
When the response of perennial grass production to
increasing soil depth was expressed on the basis of
native species (western wheatgrass, thickspike wheat -
grass, and green needlegrass) and introduced sp*CIe
(crested wheatgrass and pubescent wheatgrass), the
response patterns were essentially parallel and were not
statisically different at the 5% level. Therefore.. the
soil depth requirements for maximum productim Hof
cool - season grasses, as previously discussed, are
for either introduced grasses or native grass.
.1. E:nvlron. Qual., Vol, 13, ao, 3, 1914