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Temple, TX, United States

Jeong J.,Blackland Research Center | Jeong J.,Texas AgriLife Research Center | Santhi C.,U.S. Department of Agriculture | Arnold J.G.,Texas A&M University | Srinivasan R.,North Carolina State University
Transactions of the ASABE | Year: 2011

Onsite wastewater systems (OWSs) are a significant source of nonpoint-source pollution to surface and groundwater in both rural and suburban settings. Methods to quantify their effect are therefore important. The mechanics of OWS biogeochemical processes are well studied. However, tools for their assessment, especially at the watershed scale, are limited. As part of this work, modeling capabilities were developed within the Soil Water Assessment Tool (SWAT) such that OWSs and their subsequent environmental impacts can be evaluated A case study was initiated on the Hoods Creek watershed in North Carolina to test the new SWAT algorithms. Included were: (1) field-scale simulations of groundwater quantity (water table height) and quality (N, P), (2) Monte Carlo evaluations of OWS service life to evaluate suggested calibration parameters, and (3) assessments of watershed-scale pollutant loadings within the model. Results were then analyzed at both the field and watershed scales. The model performed well in predicting both site groundwater table levels (R 2 = 0.82 and PBIAS = -0.8%) and NO3-N concentration in the groundwater (R 2 = 0.76, PBIAS = 2.5%). However, the performance for PO4-P simulations was less reliable due to difficulty in representing the mobility of soluble P in the soil. An advanced P algorithm is recommended to address the sophisticated physiochemical properties of soil particles and improve the model's performance. © 2011 American Society of Agricultural and Biological Engineers ISSN 2151-0032. Source


McAlister J.,Blackland Research Center | Fox W.,Blackland Research Center
American Journal of Environmental Sciences | Year: 2014

The Kaw Nation and Black land Research Center in July 2012 conducted a sediment core sampling from Kaw Lake. Kaw Lake is a reservoir constructed in 1976 by the Army Corps of Engineers for the purpose of water supply and recreation. It is located 11 miles east of Ponca City, Kay County, Oklahoma. This reservoir covers approximately 17,040 acres (69 km2) and is also known to be the seventh largest lake in Oklahoma by surface area. This lake holds 428,600 acre feet (528,700, 00 m3) of water which is said to be the ninth largest lake in Oklahoma. The lake is fed by the Arkansas River that flows from Colorado, through kansas and into Kaw Lake. The Arkansas River flows through Kaw Lake shared by several small creeks and empties into the Mississippi River. The purpose of the study was to determine the rate of sediment accumulation and examine the level of nutrient and heavy metals accumulation or deposition at the bottom of the lake. Four core samples from different parts of the lake at different depth were sampled for analysis. Each core sample was sectioned into 20 cm, dried and ground into homogenous powder. Samples from each section were tested for organic carbon content and heavy metals. Organic carbon content was verified by burning through a muffle furnace, while the remaining core samples were digested into a solution and ran through an Atomic Absorption Spectrophotometer (AAS) to evaluate the concentration of heavy metals. Particle size analyses were also determined. Results were organized by depth, concentration, particle size distribution and bulk density. Data showed phosphorous and some heavy metals concentrations at core 3 and 4 were higher than core 1 and 2. Phosphorous concentration at four sediment core sites ranged from 350 mg kg-1to 550 mg kg-1. Whereas Aluminum concentration was 40,000 mg kg-1to 70,000 mg kg-1, Barium 280 mg kg-1to 420 mg kg-1, manganese 600 mg kg-1to 710 mg kg-1, iron 30,000 mg kg-1to 48,000 mg kg-1are few to be cited. Bulk density, a measure of soil mass per unit of volume of soil in a water increased with water depth as the water content decreased. © 2014 D. Alemayehu et al. Source


Meki M.N.,Texas AgriLife Research Center | Marcos J.P.,Pennsylvania State University | Atwood J.D.,Blackland Research Center | Norfleet L.M.,Blackland Research Center | And 3 more authors.
Journal of Soil and Water Conservation | Year: 2011

Corn (Zea mays L.) stover removal thresholds are subject to many site-specific factors. Current data do not provide practical stover removal guidelines for given site-specific conditions. We used the Agricultural Policy Environmental Extender (APEX) model to assess the effects of site-specific factors and corn stover removal from 3,703 farm fields within the Upper Mississippi River Basin (UMRB). From among the many management and resource attribute factors across these farm fields, we chose the site-specific factors of two land types (highly erodible land [HEL] and non-HEL), three soil textures (clayey, loamy, and sandy), four hydrologic groups (A, B, C, and D), and two management scenarios (Baseline and Enhanced Conservation Treatment) to characterize the variability of stover production potential. The Baseline management reflects farmer management practices reported in the Conservation Effects Assessment Project National Cropland Assessment database, while the Enhanced Conservation Treatment reflects additional conservation practices and management scenarios needed to mitigate sediment, nutrient, and soil organic carbon (SOC) losses. For evaluation purposes, we used the Conservation Effects Assessment Project National Cropland Assessment "acceptable planning criteria" but with more stringent SOC criteria, which does not allow stover removal on sites that lose SOC. Overall, grain and stover yields and N and P losses decreased, while sediment and SOC losses increased with increasing stover removal. On average, Baseline stover yields on HEL were slightly lower than on non-HEL, while yields were higher on loamy, followed by clayey, and then sandy soils. Hydrologic group D soils had the highest Baseline stover yields, followed by those in group B, then group C, and then group A with the lowest yields. The Enhanced Conservation Treatment management drastically mitigated sediment and nutrient losses by 69% and 57%, respectively. Differential impacts of stover removal were most pronounced among the soil textural classes, followed by soil hydrologic groups, and then land type. Overall, the findings of this research underscore the importance of site-specific factors in determining corn stover removal thresholds. For the Upper Mississippi River Basin and for sites meeting the "acceptable planning criteria," sufficiently "safe" corn stover removals are possible such that only a portion of the available corn acreage would be required to produce enough ethanol to exceed the National 2012 Energy Independence and Security Act goal. However, we do not evaluate issues associated with ethanol plant economic feasibility, such as spatial concentration of stover production. © 2011 Soil and Water Conservation Society. All rights reserved. Source

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