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SOIL SCI. SOC. AM. 3., VOL. 50, 1986 <br />trenches to within 0.23, 0.46, and 0.69 m of the <br />Topsoil (from the native William¢ loam) was then placed i <br />longitudinal strips on all trenches at thicknesses of 0.23, O. - <br />and 0.69 m to give a uniform final soil surface, each to <br />thickness occupying one -third the width of the trench. <br />were used to fill and compact the <br />in one trench for each spoil and subsoil treatment. Spoilvraa <br />replaced in the other trench of each spoil and subsoil, = <br />ment with front end loaders without compaction to sim <br />conditions created by a draghne, and to give a relay► <br />noncompacted condition_ Topsoil treatments at each <br />subdivided into two replic each of which <br />further subdivided, into three fertility a 1 <br />treatments were annual braodcast app Fertility ilia <br />were 0 kg N ha - ' and 0 kg P ha -i ;, 34 kg hal, and )4 <br />P ha -1 , and 67 kg N nd 45 ha - �, designatedihe <br />low, medium, and high fertility, vel Plots with <br />fertility treatments on undisturbed land nearby were <br />_ <br />fished to compare with yields from'•the declaimed <br />Pl ots. , ,,.,_•,.. _:, 4 .::,r 9 {. -, <br />`Olaf . wheat (Triticum aestivum - ) was growls ins <br />METHODS AND MATERIALS `Park' barley (Hordeum vulgare L) in 1980, corn, (Zed <br />L. cv. Agsco' 3x75)' in 1981; `Lew' -wheat m 1982, and <br />A site was selected in west - central North Dakota near Un- ( Pioneer 3978) in 1983. Grain and silage samples <br />derwood. The native soil was a Williams loam (fine - loamy, dried at 60 °C: Silage yields are reported at 700 g kg <br />mixed Typic Argiborolls), developed on glacial till. Average content, corn grain yields - al 150 g kg and wheat and <br />annual precipitation is 0.42 m, most of which falls in the ley yields at oven -dry weights; Yields were harvested <br />spring and summer. each subsubplot from an area 3.3 m for wheat and bars • <br />t each 16-m wide, -m rig, d from <br />Eight trenches were excavated, 58 to , to 11- m 0.76 -m a <br />, 1 ,,n8 pmt <br />- ieatine o1 <br />420 <br />0.61 m of loamy sand topsoil. Doll et al. (1984) at- <br />tributed this lack of response to thicker topsoil re- <br />placement to the droughty nature of the replaced top- <br />soil. On moderately sodic spoil (SAR = 11), yields on <br />plots covered with 0.30 m of sandy loam topsoil were <br />equivalent to yields from plots with 0.60 m of sandy <br />loam topsoil (Pole et al., 1979). <br />Concurrent with the initiation of mining north and <br />east of the Missouri River in North Dakota, experi- <br />ments were undertaken to determine topsoil and sub- <br />soil thickness requirements of nonsaline, nonsodic <br />spoil material. Treatments were incorporated into these <br />experiments to determine how N and P fertilizer, and <br />spoil compaction affected yields on topsoil and sub- <br />soil /spoil variables. Supplemental water was added to <br />selected plots in 1982 and 1983 to examine crop re- <br />sponses to irrigation. The effects of spoil compaction <br />will be discussed in another publication. <br />(Bower and Wilcox, 1965) and soluble Ca, Mg, and Na con <br />centrations were determined quantitatively using atomic ab- <br />sorption spectrophotometry. The Na bicarbonate method <br />(Knudsen, 1980) was used to determine P levels in the top- <br />soil and available K was determined from om NH: acetate ex- <br />tracts (Carson, 1980). <br />Two trenches were filled with loamy sand spoil, two with <br />clay loam spoil, and two with silty clay loam spoil to within <br />0.23, 0.46, and 0.69 m of the surface. Two additional trenches <br />were filled with loamy sand spoil to within 1.5 m of the <br />- surface (Fig. 1). Clay loam subsoil, removed from the <br />trenches, was placed on the loamy sand spoil in these two <br />Fig. 1. Cross - section of trench showing placement of topsoil, subsoil, <br />and spoil. <br />soil and fertihty treatments is subplots an <br />spectively. Yields from the irrigatedplots in 1982 kn su b s ub pIa it - <br />were dropped f�r'oont - the > an�i° <br />a1Yf varfance the no <br />gated trencli'piot"' afa idwere- yzed separatel <br />split -block c t opsoil thickness a3 the main plots i <br />tility as the subpiots.: The bidistarbed plots were'anal <br />separately`as `a rand`om`riect:�Plete block: Tukey's <br />estly significant difl'erence`(HSD) -test was.used to test" <br />nificant differences between treatment means of. each <br />ysis of variance. r i i 418' i a . • �,� ;:. , . _ <br />si2?i .3 3 115 t:4_ ;;V i 4f >c �r <br />RESULTS AND DISCUSSION <br />Thickness , topso ; significantly incr re .. <br />except for barley grain .yields in .1980 and corn_ silage <br />Table 1. Chemical and phisicel chars <br />cteriatics of soil and <br />used in the trench plot's. _ ; <br />: Gravelly <br />loamy Clay <br />Topsoil 'Subsoil r - sand loam t <br />Sand, off, 86 84 - : - 78 40 ,- <br />Silt, % 48 34 ; 13 - 31 49 <br />Clay, % - - 26 , 32 - 9 <br />Soil -water content at 0.17 0.19 0.08 0.19 <br />- 1.5MPa,m'm' . 1.4 <br />7.0 <br />10.1 r• <br />7.5 <br />2.7 - <br />� - -� <br />and 4.6 -m deep, then filled with one of three different tax Z orn. lgg2 and¢ 1483 th high Ong a trickly+ <br />tures of spoil. Physical and chemical characteristics of the noncompacted tea e s we i$a�. <br />materials are described in Table 1. Particle size distribution , , i ' gowingOn,theSe plots <br />h ter . late June - and <br />SAR - <br />Soluble Na, mmol L" <br />Soluble Ca, mmol <br />Soluble Mg, mmol <br />PH <br />EC, dSm' <br />P, kg ha"' <br />K. kg ha - ' <br />MI <br />of spoil, topsoil, and subsoil was determined using the y- l ives �fi n=igaioi ter _ . - <br />drometer method (Day, Pa 1965). W content at -1 5 M - July , and the - grovvine n �iTiee pl s m 4983. <br />was determined using pressure membrane apparatus (Rich- 152 bind mm of irrigation u► Iu an . ugu " -s = ` <br />ands, 1965). A glass electrode was used to measure pH (Peach, .. Yield data fr the.P9n Wi nch plots were a <br />1965). Soluble salts were determined on saturation extracts do " . t ,., . - <br />;t lit hlock with the su <br />as a no_nran <br />spoil by compactions tri4tmsnts as whole plots and _`�_h. <br />. <br />0.8 a 1.1 . 1.3 <br />, <br />0.7 2.0 2.8 <br />3.0 , . 1.1 - 1.0 <br />1.9 2.4 3.7 <br />7.4 7.5 " - 7.7 <br />0.9 0.7 1.0 <br />12 <br />399 <br />