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
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Table 13. Characteristics of topsoil, subsoils, and
minespoll in the Zap wedge experiment.
Material EC SAR Available Clay
Water'
mmholcm
Topsoil 1 3
Subsoils.
7 6
4 5
C ,. 1 2
Spoil 5 15
decreased. The effect of the topographic configura-
tion and slope aspect on runoff and runon of rainfall
and on the accumulation and melting of snow ap-
parently had as great an effect on crop yields as did
soil depth at thicknesses greater than 20 to 36
inches. Highest yields of crested wheatgrass were
obtained at soil thicknesses of 20 to 32 inches and
highest yields of spring wheat at thicknesses of 35
to 43 inches. Yield differences due to topographic
position were less pronounced for spring wheat than
'Gravimetric water content
1.4 -
12
1.0 -
1.6 -
.6-
d co 14 V 4 U N
0
Average Soil Depth (in.)
20 40 60
9 24
12
14
6
18
Spring Wheat
Crested Wheatgrass
45
34
13
46
Subsoils
OA
•B
oC
80 100 120
Distance from End of Plot (yards)
North South
Figure 5. Average relative yields of spring wheat (1976 and
1978) and crested wheatgrass (1978, 1979, 1981) as af-
fected by topographic location, total soil thickness and
subsoil material at the Zap double wedge experiment.
Average yield for each crop assigned relative yield 1.0.
11
for crested wheatgrass. Yield patterns of Russian
wildrye (not given) were similar to those of crested
wheatgrass.
Average yields at midslope positions (average of
both north and south positions) and for the
topographic summit (where soil thickness was
greatest) are given in Table 14. Wheat yields were
higher on plots with finer - textured moderately saline
subsoil materials (A and B) than on plots with
coarse - textured nonsaline subsoil (C) at both mid-
point and summit. Wheat yields were not ap-
preciably different between midslope and summit
positions over finer - textured subsoils (A and B);
yields over coarse - textured subsoil (C) were higher
at the midslope position. Crested wheatgrass yields
each year were somewhat higher at the midslope
position than at the summit position and were higher
over the coarse - textured nonsodic subsoil material
(C) than over the finer - textured subsoils (A and B). In
1978, a higher rainfall year, crested wheatgrass
yields were higher at the midslope position; greatest
yield differences were noted over the coarse -
textured subsoil (C).
Table 14. Average spring wheat yields for 1976 and 1978
and crested wheatgrass yields for 1978 and the average for
1979 and 1981 as affected by different subsoil materials
and topographic location at the Zap wedge experiment.
Topographic
position Subsoil
A
Midslope B
C
A
Summit B
C
Wheat Crested Wheatgrass
(1976,78) 1978 1979,1981
bu /A
15.1
13.8
10.4
14.5
14.6
7.7
tons /acre
1.39 0.60
1.45 0.71
1.74 0.86
1.35 0.52
1.38 0.53
1.16 0.75
Soil water storage in topsoil and subsoil in the
spring was consistently greater at midslope posi-
tions than at summit positions for all crops (data not
given). Soil water use (evapotranspiration) by spring
wheat was generally later in the growing season than
that of crested wheatgrass, and soil water use from
the top 2 feet during the growing season was similar
at both midslope and summit positions. Total water
use by wheat was greater on the plots with the fine -
textured moderately saline subsoils (A and B) than
on plots over the coarse - textured nonsaline subsoil
(C). With crested wheatgrass, growing season water
use was not different between the different subsoil
materials but was significantly higher at midslope
than at summit positions.
The relative effect of topographic position was
greater for crested wheatgrass than for wheat. The
most rapid period of growth and water use by
crested wheatgrass is earlier in the season than that
of wheat; therefore, crested wheatgrass would be ex-