Abstract Eight trenches were excavated to a depth of 4.6 m and filled with one of three different textures of spoil to evaluate topsoil and subsoil thickness requirements for crop production on nonsaline, nonsodic spoil material. Yields of wheat ( Triticum aestivum L.) in 1979 and 1982, barley ( Hordeum vulgare L.) in 1980, and corn ( Zea mays L.) in 1981 and 1983 were compared on plots with 0.23, 0.46, or 0.69 m of topsoil replaced over loamy sand spoil with and without subsoil, over clay loam spoil, or over silty clay loam spoil. Crop yields increased with increasing thickness of replaced topsoil, especially on trenches filled with loamy sand spoil. Crop yields were greater when subsoil was replaced than when no subsoil was replaced on loamy sand spoil at a given topsoil thickness. Average yields from the trenches were equal to or better than average yields from undisturbed plots in 1979 and 1983. On irrigated plots in 1983, response of silage and corn grain to subsoil/spoil treatments was similar to the nonirrigated plots. Wheat grown on irrigated plots in 1982 did not respond significantly to topsoil thickness or subsoil/spoil treatments. At least 0.69 m of topsoil plus subsoil was required to achieve highest yields on nonsodic, nonsaline, loamy sand spoil, but 0.46 to 0.69 m of topsoil was sufficient for highest yields on clay loam and silty clay loam nonsaline, nonsodic spoil. Crop yields were not increased by broadcast applications of N and P fertilizer.
Prairie dogs (Cynomys spp.) can influence vegetation dynamics and landscape hydrology by altering soil properties, yet few studies have evaluated soil responses to prairie dog activities across a range of soil types. This study was conducted to quantify prairie dog effects on soil properties within three unique ecological sites differing in soil and landscape attributes on a 1400 ha ranch near McLaughlin, SD. Soil properties and infiltration rate were evaluated within thin claypan, loamy, and shallow loamy ecological sites corresponding to footslope, backslope, and summit–shoulder landscape positions, respectively. Prairie dog activity was found to influence soil properties similarly across ecological sites. Prairie dog activity contributed to considerable soil heterogeneity, with on-mound areas characterized as acidified, nutrient “hot spots” compared with off-mound areas. On-mound areas possessed faster infiltration rates than off-mound areas within loamy and shallow loamy ecological sites. Soil organic C was greater in on-mound areas compared with off-mound areas, but only at intermediate depths (10 to 30 cm). Results from this study suggest postextirpation restoration efforts should consider soil heterogeneity induced by prairie dog activity within and across ecological sites.
Abstract Laboratory calibrations were used to determine the effect of coal in spoil on neutron moisture meter measurements. Calibrations were conducted on clay loam and loamy sand minespoils from western North Dakota, with and without coal added. Volumetric water contents were overestimated by 3.7% in clay loam containing 8% coal by weight, and 4.7% in loamy sand containing 9% coal by weight using a calibration curve based on similar material without coal. The equivalent water content of the coal (θ c ) was calculated from the H content of the coal. Correction of calibration curves containing coal by adding θ c to volumetric water contents substantially accounted for differences between calibration curves with and without added coal. Due to the large variability in both concentration and size of coal fragments in minespoil, accurate calibration is difficult at best. Since the slope of the calibration curve is unaffected by the presence of coal, changes in soil‐water content over time can be accurately determined from one calibration curve. At sites containing coal fragments, absolute measurements of soil‐water content are difficult, and therefore, only relative differences in water content over time should be determined.
Abstract Water redistribution in a complex landscape needs to be quantified in order to determine field productivity. Landscape effects on water use and spring wheat ( Triticum aestivum L.) yields were studied by monitoring two fields at each of two locations in North Dakota for 5 years. Four soil series at different positions within each field were monitored: the Zahl loam series (fine‐loamy, mixed Entic Haploboroll) on hilltops and shoulder positions, the Williams loam series (fine‐loamy, mixed Typic Argiboroll) on side slopes and hilltops, the Bowbells loam series (fine‐loamy, mixed Pachic Haploboroll) on footslopes and toeslopes, and the Tonka silt loam series (fine, montmorillonitic, frigid Argiaquic Argialboll) in small undrained depressional areas. Topographic factors were calculated at each site by measuring the slope in four directions, 90° apart, and adding the slopes together. If a slope was downward toward a site, it was considered positive, if a slope was upward toward a site it was considered negative. This number, if positive, would indicate that runon water would be added to the site and, if negative, water would be lost from the site due to runoff. Topographic factors were calculated 3, 6, 15, and 30 m from each site. As expected, wheat yields from the four soils were in the order Tonka > Bowbells > Williams > Zahl. Spring wheat grain yields ranged from 5.1 Mg ha −1 on Bowbells in 1985 to no yield in 1988 at the Underwood location. Spring wheat grain yields were generally correlated to total water use. When the topographic factor was added into the regression of yield vs. total water use, the coefficient of determination, R 2 , increased in the first 3 yr. The last 2 yr of the study were drought years and the topographic factor accurately reflected the lack of water redistribution in those years. Topographic factors measured 15 m from the site gave the highest R 2 values.
Soil water retention and transport functions are needed to model infiltration and redistribution of water in reclaimed mineland profiles. Besides primary particles of sand, silt, clay, and rock fragments, some mineland soil profiles in west-central North Dakota also contain lignite coal fragments ranging in sizes from <1 to about 300 mm or more. The objective of this study was to evaluate the water retention properties of soil mixed with coal fragments. For preliminary investigations in the laboratory, disturbed soil and coal samples of sizes <2.0 mm were used. Two types of coal samples, one commercial lignite with high water repellency and the other a degraded lignite with low water repellency, were mixed with three types of soils. The soil samples collected from subsoil and minespoil materials of reclaimed minelands included a sandy loam, a loam, and a sodic silty clay loam (equivalent to premine B and C horizons of Straw loam, a fine-loamy, mixed Cumulic Haploboroll). Air-dry samples of soil and coal were thoroughly mixed and bulk mixtures with coal contents of 5, 10, 15, 25, and 50% by oven-dry weight were produced. The subsamples of the components and the mixtures were wetted with water and desorbed at air pressures ranging from 5 to 1500 kPa. Water contents of the mixtures, in general, were linearly proportional to the coal contents. From the soil water content vs. pressure head relationships of ingredient soil and coal samples, volumetric water contents of soil-coal mixtures were predicted by using mass and volume balance interpolation equations. At all pressures heads, the predicted volumetric water contents approximated the measured values with a high degree of accuracy.
