Land-use effects on soil-water retention characteristic

Tillage can negatively affect soil physical properties such as bulk density, organic matter content, and soil hydraulic properties, which in turn affect how plants grow. The objective of this study was to evaluate water retention characteristics of a Jay silt loam soil under cultivated agriculture and native tallgrass prairie in northwest Arkansas. Air-dry soil samples collected from 0-10 cm depth were re-wet with varying amounts of distilled water to create a range of water contents. After overnight equilibration, the water potential was measured on the re-wet soil samples using a dewpoint potentiameter. The relationship between water potential (Ψ) and water content (θv) for the cultivated agricultural and undisturbed prairie soil was modeled using the equation Ψ = aθv –b, where a and b are coefficients determined from fitting the data and represent the water retention characteristics for the soil of the two different land uses. The a and b coefficients did not differ significantly due to land use. Therefore, the results of this study did not support our hypothesis that agricultural land use significantly affects water retention characteristics. However, increasing the number of soil samples in which the water potential was measured could have sufficiently decreased the variability in the a and b coefficients so that significant differences in water retention characteristics as a result of land use could have been demonstrated

Using combined prediction models to quantify and visualize stormwater runoff in an urban watershed

Stormwater runoff can transport nutrients, sediments, chemicals, and pathogens to surface waterbodies. Managing runoff is crucial to preserving water quality in rapidly developing urban watersheds like those in Northwest Arkansas. A watershed containing the majority of the University of Arkansas campus was designated as the study area because stormwater from it drains into the West Fork of the White River, designated as an impaired waterbody due to siltation. The project objective was to develop methodology to test existing stormwater drainage infrastructure, identify potential areas of improvement, and estimate potentially contaminated runoff by combining two widely used prediction models. The U.S. Department of Agriculture’s Natural Resource Conservation Service’s curve number (CN) method was used to estimate runoff depths and volumes, while a flow-direction model was created that integrated topography, land use, and stormwater drainage infrastructure in a geographic information system. This study combined the CN and flow-direction models in a single geodatabase to develop flow direction/quantity models. Models were developed for 5-, 10-, 25-, 50-, and 100-year floods and varied by the antecedent moisture content. These models predicted flow directions within existing drainage infrastructure and runoff volumes for each flood, and served as a hypothetical flood analysis model. Results showed that between 24,000 m3 (5-year flood) and 60,000 m3 (100-year flood) of runoff would be transported to the West Fork of the White River. The methodology developed and results generated will help stormwater planners visualize localized runoff, and potentially adapt existing drainage networks to accommodate runoff, prevent flooding and erosion, and improve the quality of runoff entering nearby surface waterbodies

Effects of vegetation removal on native soil quality in eastern Arkansas

Aboveground vegetation removal practices, such as cutting and baling and burning, can both positively and negatively affect a prairie ecosystem. Burning can stimulate growth and species diversity, but removing vegetation and the nutrients it contains without equal replenishment of those nutrients could cause a steady decline in available soil nutrients. The objective of this study was to evaluate the effects of vegetation removal techniques in a native tallgrass prairie in eastcentral Arkansas. Soil samples were collected from the top 10 cm in each soil mapping unit that existed in each of three prairie areas that differed by the amount of time since aboveground vegetation had been removed by cutting and baling (i.e., 0, 6, and 24 years). Soil samples were analyzed for bulk density, particle-size distribution, organic matter, pH, electrical conductivity (EC), and extractable nutrients. Bulk density and EC were highest in the prairie area in which vegetation removal by cutting and baling still occurs at the present, but organic matter was highest in the prairie area in which cutting and baling ceased in 1998 (i.e., 6 years prior). Soil pH was highest in the prairie area in which cutting and baling ceased in 1980 (i.e., 24 years prior). No consistent trends among the three prairie treatments existed for extractable soil nutrients. The results of this study indicate that common prairie management practices in the Grand Prairie region of east-central Arkansas significantly affect soil physical and chemical properties. Prairie management practices need to be considered carefully to insure long-term sustainability and proper ecosystem functionin

Rice Biomass Response to Various Phosphorus Fertilizers in a Phosphorus-Deficient Soil Under Simulated Furrow-Irrigation

Wastewater-recovered phosphorus (P), in the form of the mineral struvite (MgNH4PO4∙6H2O), may provide a sustainable alternative to decreasing rock-phosphate reserves. Struvite can be generated via precipitation methods, potentially reducing the amount of P runoff to aquatic ecosystems. The objective of this greenhouse tub study was to evaluate the effects of chemically and electrochemically precipitated struvite (CPST and ECST, respectively) on aboveground plant response in a hybrid rice cultivar grown using furrow-irrigation compared to other common fertilizer-P sources [i.e., triple super phosphate (TSP) and diammonium phosphate (DAP)] using three replications of fertilizer treatment in a P-deficient silt loam (Typic Glossaqualfs). Aboveground rice dry matter (DM), aboveground DM P uptake, grain yield, and grain P uptake from CPST and ECST did not differ from DAP or TSP. However, aboveground DM P concentration was numerically largest (P \u3c 0.05) from TSP (0.05 %), which did not differ from DAP, and was at least 2.5 times larger than that from ECST, CPST, and the unamended control (UC). Similar rice responses among struvite and other common fertilizer-P sources suggest CPST and ECST are both possible alternative fertilizer-P sources that warrant further research into struvite’s role in food production and water quality restoration and preservation

Bermudagrass growth in soil contaminated with hydraulic fracturing drilling fluid

Hydraulic fracturing is the process of injecting aqueous solutions at high pressure to break apart rock formations and increase the extraction of natural gas. The solutions are recovered and have been land-applied as one disposal technique. Excessive fluid application can result in increased soil salinity that can inhibit plant growth. The objective of this greenhouse study was to evaluate the effects of inorganic fertilizer, broiler litter, and Milorganite® and soil depth interval (0-15 cm or 0-30 cm) on the growth of bermudagrass [Cynodon dactylon (L.) Pers] in soil that was collected from a site that had been contaminated with fracturing fluid and was initially devoid of vegetation. Amendment rates were added to provide 60 mg of plant-available N/kg. Bermudagrass was sprigged and harvested after nine weeks and shoot, root, and total biomass were determined. Addition of inorganic fertilizer, broiler litter, or Milorganite® resulted in greater shoot biomass compared to unamended soil. Plants grown in 0-30-cm-depth soil had greater root biomass compared to the 0-15-cm soil depth. The addition of recommended plant nutrients and mixing of the contaminated surface soil with the subsurface soil enhanced bermudagrass growt

Soil particle-size analysis: A comparison of two methods

Knowing the proportion of particle sizes in soil is important to soil scientists and agronomists. The mixture of sand, silt, and clay influences water movement, solute transport, nutrient retention, and many other properties and processes in soil. The standard method for particle size determination is a somewhat time-consuming process. An equally accurate but shorter method would be appealing for many reasons. The objective of this study was to compare a standard method of particle-size analysis using a hydrometer to an abbreviated hydrometer method, which, instead of 12 h for the standard method, requires about 3 h to complete. Twenty-four soil samples of varying textural classes determined by the standard method were reprocessed for particle-size and textural-class determination using an abbreviated hydrometer method. Results of the methods comparison showed that the textural class from the abbreviated method matched that of the standard method in only 10 of 24 samples and that the abbreviated method over-estimated the amount of total sand in the soil sample. The abbreviated method was reasonably accurate in comparison to the standard method with respect to percentages of clay and silt. Based on this comparison, the time savings gained with the abbreviated method do not outweigh the lack of accuracy of particle-size determination with coarsetextured soils, but may be justifiable for fine-textured soils without a large fraction of sand-sized material

Corn response to wastewater-recycled phosphorus fertilizers

The ability to recycle phosphorus (P) from wastewaters could provide a sustainable, continuous source of P that might also help protect surface water quality from P enrichment. The mineral struvite (MgNH4PO4 · 6H2O) is an understudied material that can be created from P- and nitrogen (N)-containing wastewater and has been shown to have agricultural fertilizer value. The objective of this study was to evaluate the effects of electrochemically precipitated struvite (ECST), chemically precipitated struvite (Crystal Green; CG), diammonium phosphate (DAP), monoammonium phosphate (MAP), rock phosphate (RP), and triple superphosphate (TSP) on corn (Zea mays) response in a greenhouse pot study. The effects of fertilizer treatment on select plant properties were evaluated. Corn plant properties and elemental tissue concentrations differed (P \u3c 0.05) among fertilizer amendments. Belowground dry matter from ECST was 1.9 times greater than that from CG, TSP, DAP, and the No P/+N, and No P/-N control treatments. Corn cob-plus-husk tissue P concentration from ECST was similar to that from MAP and DAP and was 1.2 times larger than that from CG. Corn stem-plus-leaves tissue P concentration from ECST differed from that from all other treatments and was 1.8 times greater than that from the No P/+N control. Results generated from this study not only provide information on the new, thus understudied, electrochemically precipitated struvite material, but also further demonstrate why more research should be conducted on the implementation of struvite as an alternative fertilizer-P source and struvite’s potential impact on sustainable food production and the preservation of water resources

Rice Biomass Response to Various Phosphorus Fertilizers in a Phosphorus-Deficient Soil Under Simulated Furrow-Irrigation

Wastewater-recovered phosphorus (P), in the form of the mineral struvite (MgNH4PO4∙6H2O), may provide a sustainable alternative to decreasing rock-phosphate reserves. Struvite can be generated via precipitation methods, potentially reducing the amount of P runoff to aquatic ecosystems. The objective of this greenhouse tub study was to evaluate the effects of chemically and electrochemically precipitated struvite (CPST and ECST, respectively) on aboveground plant response in a hybrid rice cultivar grown using furrow-irrigation compared to other common fertilizer-P sources [i.e., triple super phosphate (TSP) and diammonium phosphate (DAP)] using three replications of fertilizer treatment in a P-deficient silt loam (Typic Glossaqualfs). Aboveground rice dry matter (DM), aboveground DM P uptake, grain yield, and grain P uptake from CPST and ECST did not differ from DAP or TSP. However, aboveground DM P concentration was numerically largest (P \u3c 0.05) from TSP (0.05 %), which did not differ from DAP, and was at least 2.5 times larger than that from ECST, CPST, and the unamended control (UC). Similar rice responses among struvite and other common fertilizer-P sources suggest CPST and ECST are both possible alternative fertilizer-P sources that warrant further research into struvite’s role in food production and water quality restoration and preservation

Landuse and Physiographic Region Effects on Soil Carbon and Nitrogen Sequestration in Arkansas

Increasing understanding of soil carbon (C) sequestration dynamics and general functioning in disappearing native grassland ecosystems, has the potential to enhance soil rehabilitation and ecosystem restoration. The objective of this study was to evaluate the effects of landuse (native tallgrass prairie and managed agriculture) and physiographic region (northwest Arkansas and east-central Arkansas) on the change in soil C and nitrogen (N) storage and other soil properties over a 15-year period. Despite the native prairie losing soil C at a rate of 4.7 Mg ha−1 year−1 over the 15-year duration of this study, soil C storage in 2016 was more than 2.5 times greater in the native prairie than in the cultivated agroecosystems in the Grand Prairie. Averaged across landuse, TC concentration (P < 0.01) and content (P < 0.01) changed more over time in the Ozark Highlands region of northwest Arkansas (0.02% year−1 and 0.28 Mg ha−1 year−1, respectively), than in the Grand Prairie region of east-central Arkansas. This study demonstrates the value of direct measurements over time for assessing temporal changes in soil properties and results can potentially direct future restoration activities to be as successful as possible

Dilute-acid-extractable phosphorus, arsenic, and selenium in weathered and fresh coal fly ash

Fly ash is a byproduct of the combustion of coal, primarily by coal-fired power plants. Over 97.8 million tonnes of fly ash are produced each year in the United States. Fly ash can contain trace elements in concentrations that can cause health risks. Recent spills have highlighted that fly ash disposal is problematic. The objective of this study was to evaluate the effects of fly-ash type (fresh and weathered) from a local coal-burning power plant and extraction time (2 and 6 h) on dilute-acid extractable concentrations of phosphorus (P), arsenic (As), and selenium (Se). Ash samples were extracted with 0.1 M HCl and shaken for either 2 or 6 h. Extracts were analyzed by inductively coupled argon plasma mass spectrometry. Phosphorus concentrations increased with the longer extraction time, but there was no significant difference between ash type. Arsenic and Se concentrations were greater in fresh ash and decreased with longer extraction time in fresh ash, but no difference between extraction times was observed in weathered ash. It was determined that P concentrations were not related to As and Se concentrations, but were possibly dependent on calcium phosphates because of the high pH of fly ash. The lower As and Se concentration in the fresh ash, 6-h extraction, as compared to the 2-h extraction suggests that a process analogous to environmental weathering occurred during extraction. Research into the behavior and speciation of these insoluble forms will help explain movement and behavior of trace elements in fly ash