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Agricultural activities can accelerate the offsite transport of productive soil from fields leading to stream water quality degradation. Identification of the nature and relative contribution of different sources to fine-grained sediment (e.g., silts, clays) in streams is important to effectively focus agricultural best management practices in watersheds. Sediment fingerprinting techniques through the use of geochemical tracers are commonly used to differentiate relative contribution from various sources. Research was conducted in lowland streams in the Pleasant Valley watershed in South Central Wisconsin (USA) to identify provenance of fine-grained sediment deposits and evaluate the impact of land use on relative contributions from the following potential sources: cropland, pasture, woodland, and eroding stream banks. Results show that both agriculture (croplands and pastures) and eroding stream banks are primary sources to fine sediment deposits on the stream bed with contributions ranging from 19 to 100% and 0 to 81%, respectively. The increase in area under agricultural land use within a subwatershed results in greater contribution from agriculture (R 2 = 0.846, p = 0.0034). Relative contributions from eroding stream banks increased with increasing area under grasslands and woodlands within a subwatershed (R 2 = 0.814, p = 0.0055). Subwatersheds with greater mass of fine sediment deposited on the stream bed per unit area should be prioritized for best management practices. The conservation practices should be targeted to stream banks or croplands depending on the dominant source of fine sediment within a subwatershed. Site specific changes in relative contributions from different sources to fine-grained sediment in this watershed highlights the complexities involved in sediment transport dynamics. The nested sampling sites helped determine that sediment dynamics at the subwatershed scale need to be considered for application of targeted conservation techniques. [ABSTRACT FROM AUTHOR]

• Macropore characteristics were quantified as a function of land use and tillage. • Land use and tillage influenced pores in surface soils (0–100 mm) substantially. • Effect of land use and tillage on pores of different sizes was not similar. • Larger soil cores can help capture variability in soil macropore characteristics. Quantification of soil macropores is important to enhance our understanding of preferential flow behavior in soils. However, knowledge of 3D soil architecture for different land uses in a continental climate region is limited. X-ray computed tomography is a novel technique that can provide valuable information about the 3D features of the soil, such as connectivity, length density, and tortuosity, that largely control water flow through the macropores. In this study, X-ray computed tomography and image analysis were employed to quantify the soil macropore characteristics from four combinations of different land uses and soil tillage practices - native grassland (Nat), alfalfa (Alf), conventional till-corn (CT), and no-till corn (NT) systems. A total of 15 undisturbed soil columns, 150 mm in diameter and 500 mm in length, were collected from different fields. The macropore characteristics were distinctively different for different land use and tillage treatments, especially near the surface depth (top 100 mm). The soil macropores under CT were highly connected and concentrated mostly in the surface soil layer. In contrast, macropores under NT were larger and had well-developed pore networks. The Alf field had relatively larger and more vertically oriented macropores as compared to the Nat field. Relatively larger macroporosity and a higher number of macropores were observed in the surface of soils collected from Nat field. Macropore characteristics were mostly similar between Alf and NT treatments. The results of this study facilitate quantitative evaluation of 3D soil macropore features with significant implications for non-equilibrium flow prediction and contaminant transport modeling in soils. [ABSTRACT FROM AUTHOR]

Excessive delivery of fine-grained sediment and sediment-bound nutrients to surface waters results in water quality impairment. Information on the relative contribution of different sources contributing sediment to river systems is a prerequisite to target management practices. The overall goal of this study was to determine the sources of stream bed sediment at a subwatershed scale using sediment fingerprinting approach in an urbanized, 31 km2 Moore's Mill Creek watershed in Southern Piedmont region in Alabama, USA. The relative source contribution from construction sites and stream banks was quantified for two different particle size fractions, 63–212 μm (fine sand) and <63 μm (silt and clay). Results of this study showed that both construction sites and stream banks were important sources of stream bed sediment. The stream bed sediment in the upstream reaches originated largely from channel bank sources, and in the lower reach (watershed outlet), construction sites were the dominant sources of stream bed sediment. The results of this study showed that the relative source contribution from different sources is dependent on the particle size of the sediment, time and location of sampling within a watershed, riparian buffers, and areas of construction activities in proximity to the sampling sites. Conservation practices in this watershed should be targeted to stream banks or construction sites depending upon the dominant source of stream bed sediment within a subwatershed. Overall, this study underscores the importance of considering the spatial and temporal variability of sediment sources as a function of sediment particle size for targeted implementation of best management practices. • Sediment fingerprinting technique was used to identify sediment sources. • Construction sites and stream banks were investigated as sources of sediment. • Relative source contributions to stream bed sediment varied with particle size. [ABSTRACT FROM AUTHOR]

Site-specific soil hydraulic properties (SHPs) are critical for determining irrigation thresholds and adopting the best irrigation practices. In this study, we optimized two single-layer SHPs for two management zones (namely, zone 1 and zone 2) delineated in a crop field using topographic attributes, soil texture, and historical crop yield to demonstrate the need for zone-specific SHPs. The inverse HYDRUS-1D model was used to optimize a single-layer zone-specific SHPs using multilayered observed soil water pressure heads (h) measured in both zones. Statistical indices for goodness of fit showed that a single layer SHPs simulate h during the growing season well. The irrigation thresholds and amounts determined using zone-specific optimized SHPs were used to trigger irrigations. Different irrigation scenarios using 15 cm, 30 cm, and 60 cm soil depths were developed using the zone-specific optimized SHPs in the HYDRUS-1D model to meet irrigation water demand and reduce water stress. The ratio of actual root water uptake (ARWU) and potential root water uptake (PRWU) were calculated to compare improvements in satisfying daily water demand and to reduce the water stress under different irrigation scenarios. Out of the total irrigation water triggered during growing seasons, greater than 61 % and 75 % in zone 1 was triggered in July 2018 and in May-June 2019, respectively. However, greater than 73 % in July 2018 and greater than 72 % in May-June 2019 were triggered in zone 2. Based on the simulations of various irrigation scenarios in HYDRUS-1D, we found that installing sensors at 15 cm or 30 cm can help meet the daily irrigation water demand on time than sensors at 60 cm depth. This study discussed the importance of critical water demands due to the distribution of precipitation over the growing season and need of zone-specific optimized SHPs for site-specific irrigation management within the field. • Raw or observed soil hydraulic properties showed variability across the field. • Soil hydraulic properties were optimized using multilayered soil water pressure. • Irrigation thresholds were optimized using optimized soil hydraulic properties. • Irrigation scenarios improved actual root water uptake during growing seasons. • Sensor installation was recommended at 15 cm and 30 cm depths to trigger irrigation. [ABSTRACT FROM AUTHOR]

Phosphorus (P) and Ammonium Nitrogen (N) are essential nutrients for plants and environmental stability. However, their excess in water causes eutrophication, damaging aquatic ecosystems. While adsorption is a promising solution, finding affordable and efficient adsorbents remains a challenge. In this study, magnesium (Mg), iron (Fe), and Mg/Fe doped biochars (BC) adsorbents were synthesized, and evaluated for adsorption of individual P and N and a P + N mixture from a solution and wastewater from a wastewater treatment plant. Compared to other adsorbents, Mg/BC showed excellent performance in adsorbing phosphorus (P) and ammonium nitrogen (N) from aqueous solutions. It demonstrated a large adsorption capacity of 64.65 mg/g and 62.50 mg/g from individual P and N solutions, and 30.3 mg/g and 27.67 mg/g from the P and N mixture solution, respectively. In addition, Mg/BC efficiently removed P and N from real-life wastewater. In the real wastewater, P and N removal efficiencies reached 88.30% and 59.36%, respectively. Kinetics analysis revealed that the pseudo-second-order model accurately described the adsorption of phosphorus (P) and ammonium nitrogen (N) in all solutions. The adsorbent followed the monolayer-Langmuir isotherm for N ions and the multilayer-Freundlich isotherm for P, indicating efficient adsorption processes. Thermodynamic experiments indicated that the adsorption of P and N was not only feasible but also occurred spontaneously in a natural manner. This study revealed that the strategic modification of biochar plays a crucial role in advancing effective wastewater treatment technologies designed for nutrient removal. [Display omitted] • Air calcined metal chloride adsorbents were devolved for P & N adsorption from wastewater. • Maximum adsorption P (64.65 mg/g) & N (62.50 mg/g) was found with Mg/BC adsorbent. • Efficiently simultaneous adsorption of P & N was achieved by Mg/BC adsorbent. • P and N adsorption mechanisms were studied. [ABSTRACT FROM AUTHOR]