The Rhoades and Wade series of two Solonetzic (Sodic) soil associations in the Chestnut great soil group (Mollisols) in western North Dakota were characterized with respect to chemical and physical properties. Infiltration and vegetative growth were directly proportional to thickness of A horizons and inversely related to exchangeable Na percentage (ESP) of the claypan. The impervious claypan in Rhoades frequently had < 15 ESP but lower horizons had higher ESP values. The claypan and lower horizons of Wade usually had ESP's > 15. Concentration of adsorbed cations in claypan layers of both associations were Mg > Ca > Na > H. The H was present only in the upper few centimeters. The principal soluble salts of the Rhoades association were sulfates of Na, Mg, and Ca listed in decreasing order of occurrence, with total concentration usually < 120 meq/liter of saturation extract. Soluble salts of the Wade association greatly exceeded those found in Rhoades; the Wade series contained nearly equal concentrations of Na and Mg sulfates. The results suggest that remedial treatment on Rhoades soil should consist of deep plowing to destroy the claypan and to include calcareous subsoil. Gypsum or sulfur might also be beneficial. The reclamation of Wade soil will require additional and more intensive treatments.
We studied the movement of sodium and other ions in sodic strip-mine spoils reclaimed by soil spreading. In columns containing two different soils placed over minespoil, both model calculations and measurements indicated that considerably more Na migrated upward by salt diffusion than by convective flow generated by soil-water evaporation. More Na movement occurred in columns without evaporation than in columns with evaporation: reduced water contents reduced diffusion, and very low minespoil hydraulic conductivity severely restricted convective flow. Application of column results and model calculations to field observations of salt movements in topsoil-covered minespoils under semiarid, continental climatic conditions indicated that salt diffusion is a significant mechanism for Na accumulation in soil, provided the spoil is highly dispersed and the necessary chemical gradient is present. However, these calculations and data both indicate that significant quantities of Na would diffuse only 10 to 15 cm upward in materials of this nature.
Data by which we can quantify effects of soil depth upon productivity from controlled experiments are essentially lacking for semiarid regions. In connection with mined land-reclamation research in North Dakota, an experiment was established in which soil was reconstructed by building a wedge with productive subsoil (B and upper C horizon) on top of leveled sodic mine spoils derived from shale. Thickness of the subsoil wedge ranged from 0 to 210 cm. Topsoil (A horizon) was then spread over the subsoil wedge to provide a topsoil either 0, 20, or 60 cm thick. A fourth treatment consisted of mixing subsoil and topsoil within the wedge in a 3:1 ratio (no topsoil on the surface). Four crops—alfalfa (Medicago sativa L.), crested wheatgrass (Agropyron desertorum), native warm-season grasses (Bouteloua gracilis and Bouteloua curtipendula), and spring wheat (Triticum aestivum L.)—were grown each year on these plots from 1975 through 1979. Yields of all crops increased as total soil thickness (topsoil plus subsoil) increased to the 90- to 150-cm range. Highest yields equaled or exceeded yields that would be expected in these years on similar undisturbed soil types under good management in the same county. In most instances, over 90% of the maximum yields observed was obtained when 70 cm of subsoil plus 20 cm of topsoil covered the sodic spoils (SAR = 25, clay = 38%). Yields from 60 cm of topsoil were similar to those from 20 cm of topsoil. With no topsoil, only native grama grasses produced over 75% of maximum, but all crops except wheat produced at least 90% of maximum with at least 90 cm of the mixed subsoil-topsoil spread over spoils (wheat yields were only about 80% of maximum). Water was extracted from the upper 30 to 90 cm of spoils when the soil-spoil interface was within 90 cm of the soil surface. Thickness of topsoil had no influence on depth of water extraction. Alfalfa extracted water to about 135 cm if sodic spoils were within 90 cm of the surface and to about 175 cm where spoils were covered with at least 150 cm of soil materials. Depth of water extraction by crested wheatgrass under these two situations was about 120 and 150 cm; by native grasses about 80 and 120 cm; and by spring wheat about 75 and 90 cm, respectively. There was no evidence of any accumulation of soil water just above the soil-spoil interface under any situation.
A field experiment was conducted to evaluate soil water, water table, and soil temperature relations in an area having a high water table, saline soil, and artesian water. The water table during winter lowered owing to upward migration of ground water toward the colder surface soil. However, the water content of the 2.7‐meter soil profile increased in an amount of water exceeding that accountable by the drop in the water table, precipitation, and horizontal flow. The additional water was most likely contributed from the artesian aquifer underlying the area.
We analyzed effluents from subsurface drains installed to intercept flow from two saline seeps to evaluate chemical composition as a function of time and drain flow rate. The seeps were discharges of saline groundwater on upland hillside sites as contrasted to lowland or depressional sites that impound water. Electrical conductivity of the drain water ranged from 7 to 13 millimhos per centimeter. Magnesium sulfate and sodium sulfate were the predominant dissolved salts, calcium concentrations were consistently low, and nitrate concentrations were high enough to make the waters unfit for human consumption and a potential hazard to the health of livestock. The nitrate seemed to come from two sources—exchangeable ammonium of geologic origin oxidized to nitrate deep in the profile and nitrate leached from the root zone during the fallow period. Salt concentrations were not related to drain flow rate. During the 5-year study, effluent from the drains amounted to a surface-depth equivalent of 6.9 centimeters of water for the recharge area and contained the equivalent of 6100 kilograms of dissolved salt and 50 kg of nitrogen per hectare of recharge area. However, two-thirds of both the water and the salt were discharged during 1 year. Even though seeps can be hydrologically controlled by installing interceptor drains, drainage may be environmentally unacceptable because of the dissolved salt load. The best approach is to utilize the soil water while it is a nonsaline resource in the root zone of the recharge area.
Soil salinity can frequently be reduced and controlled under dryland conditions of the Northern Plains by proper use of dryland cultural practices that promote soil water conservation. Summer fallow significantly reduced salinity in the root zone, whereas salinity increased under a small grain crop. Soil salinity reductions attributed to fallow were greater under a deeper water table regime compared to more shallow water table conditions. A straw cover or small grain stubble mulch during the winter, in conjunction with summer fallow, led to further salinity reductions. The straw mulch was more effective in reducing salinity at a more severely saline and higher water table site than at a more moderate location. Summer fallow was more effective at the more moderate site compared to the severe location. Under the combination of summer fallow and winter vegetative mulch, precipitation in excess of evapotranspiration losses supplied water for leaching. Growing a crop, except during high rainfall periods, did not leave excess water. Our findings suggest that summer fallow with winter vegetative residue management can be effectively utilized in the cultural rotation for reducing soil salinity under dryland conditions.
Exchangeable ammonium nitrogen is present in Paleocene (Fort Union) shale below a depth of 10 meters in North Dakota and eastern Montana. Above 10 meters, exchangeable ammonium nitrogen is nitrified in situ. The lack of viable nitrifying organisms and the probable lack of oxygen prevent in situ nitrification below 10 meters. Shale samples incubated at 27°C under nonsterile conditions or shales exposed to atmospheric contamination exhibited active nitrification without additional treatment.
Abstract Numerous factors affect the composition and quality of crops. One of these factors is soil thickness, which can affect quantity of nutrients available, availability of water, and rooting depth. This experiment was conducted in North Dakota to determine the effects of variable thicknesses of topsoil and subsoil over sodic mine spoils on nitrogen (N) and phosphorus (P) concentrations in blue grama and side oats grama ( Bouteloua gracilis and Bouteloua curtipendula ), crested wheatgrass ( Agropyron desertorum ), alfalfa ( Medicago sativa ), and hard red spring wheat ( Triticum aestivum ). Milling and baking qualities of spring wheat were also evaluated. Total phosphorus concentration in most crops was not consistently affected by subsoil thickness; however, total P in plant material was usually greatest when subsoil was covered with either 20 or 60 cm of topsoil. Mixing subsoil and topsoil in a 3:1 ratio frequently gave plant P concentrations almost as low as for treatments of no topsoil over subsoil. A notable exception was alfalfa. Plant nitrogen concentration tended to decrease as subsoil thickness increased. Much of this decrease may have resulted from simple dilution, since total plant growth generally increased as total soil thickness increased to 90 to 120 cm. Except for alfalfa, N concentration was greater in all crops produced on 20 to 60 cm of topsoil over subsoil than on plots with no topsoil or subsoil and topsoil mixed. Generally, milling and baking properties of the wheat grain were closely related to the grain N concentration. Based on several parameters of milling and baking quality, flour from wheat produced on plots with 20 or 60 cm of topsoil generally was superior in milling and baking properties to flour from wheat on plots with no topsoil or with subsoil and topsoil mixed. In general, presence of topsoil affected crop quality by enhancing nutrient uptake by the plant. On the other hand, increased subsoil thickness often increased rooting depth and water availability, resulting in increased plant growth and, consequently, dilution of nutrient concentrations in the crops produced.
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