Rainfall Simulation Study Research Articles

Potential Release of Phosphorus by Runoff Loss and Stabilization of Arsenic and Cadmium in Mining-Contaminated Soils with Exogenous Phosphate Fertilizers

Phosphate has been proven to be effective in remediating soils contaminated with potentially toxic elements (PTEs); however, the potential release of phosphorus (P) through runoff and the impact on PTEs’ transport in this process have never been assessed. A rainfall simulation study was conducted to investigate P runoff loss and its impact on the stability of arsenic (As) and cadmium (Cd) after applying potassium dihydrogen phosphate (PDP), superphosphate (SSP), and ground phosphate rock (GPR) in soil trays packed with As–Cd-contaminated soil. The phosphorus loss through runoff and sedimentary phases followed the order of SSP > PDP > GPR > control. Phosphate fertilizers’ application reduced the mobility of As and Cd. In the first rainfall, the enrichment ratios (ERs) of As and Cd in the sedimentary phase after PDP, SSP, and GPR treatment were 0.12, 0.04, and 0.08 and 0.24, 0.16, and 0.07 units lower than the control, respectively. The <53 μm fraction in the sedimentary phase accounted for 53.06–75.95%, and phosphate fertilizers significantly enhanced the As and Cd stability in this fraction. The XPS analysis showed that the conversion of As(III) to As(V) and the generation of Cd–phosphate compounds were important reasons for enhancing As and Cd stability. This study demonstrated that PDP might be capable of the remediation of As–Cd contamination with the least release of P to watersheds.

Impact of broiler litter and swine liquid manure on nutrient loss in runoff from three consecutive one acre-inch rainfall events

Manure is an important source of plant nutrients and organic matter that can benefit soil health over time. However, indiscriminate use of manure can lead to environmental problems including eutrophication of water bodies caused by nutrient runoff during precipitation events. There is a need to understand the effect of manure source and application rate on nitrogen (N) and phosphorus (P) forms and their losses during runoff events. In this study, we assessed the impact of application rate of broiler litter (BL) and swine liquid manure (SLM) on runoff volume, soil, N, and P losses using a rainfall simulator and three consecutive 2.45 cm rainfall events. Surface Decatur silty clay loam (0–0.06 m) was collected and packed in trays (0.55 x 0.30 × 0.06 m3). Manure was surface-applied to the soil at equivalent P rates ranging from 62 to 249 kg ha−1 for BL and 5–18 kg ha−1 for SLM, respectively. Rainfall events took place 7, 14, and 21 d after manure application. Results indicated that the runoff volume decreased at the highest manure application rate compared to the lowest manure application rate. The total suspended solids (TSS) loss was lower in control compared to BL and SLM treatments. The loss of nitrate-N (NO3-N) dissolved reactive P (DRP) and dissolved organic P (DOP) in runoff water was maximum at the highest application rates for both the BL and SLM with respect to control. Mehlich 3 extractable P (M3P) and water soluble P (WSP) increased with increasing P application rates for both manure types in soils following post rainfall simulation study. An increase in M3P and WSP, along with a decrease in soil P storage capacity following post-rainfall simulation for higher P application rates, indicates caution should be taken for considering the manure application rate to prevent environmental nutrient loss during runoff events.

Evaluating the Effectiveness of the Biodegradable Superabsorbent Polymer (Fasal Amrit) on Soil Hydrological Properties: A Laboratory Rainfall Simulation Study

Superabsorbent polymers (SAPs) are effective soil amendments that can control soil erosion by improving soil quality. However, many commercial SAPs face challenges including limited biodegradability, high costs, and adverse effects on soil hydrological properties, which can lead to increased water and soil loss. This study examined the potential of lower dosages of biodegradable SAPs to improve the hydrological properties of “Shimajiri-maji” (clay) soil. Three concentrations of biodegradable Fasal Amrit polymer (EFP) (P1: 0, P2: 3 g m−2, and P3: 6 g m−2) were evaluated under three simulated rainfall intensities (I1: 35; I2: 70 and I3: 110 mm h−1) and two gradients (7.5%, and 15%) during consecutive storms. The time to generate runoff, infiltration, runoff, soil loss, and water storage (WS) were quantified over one hour. The results show that runoff generation was delayed in EFP-treated soils compared to the control. Both polymer treatments enhanced infiltration (P2 > P3 > P1) and reduced runoff and soil loss (P2 < P3 < P1). Higher EFP rates improved water storage at surface depths (P3 > P2 > P1). EFP-treated soils exhibited lower interrill erodibility, suggesting greater resistance to soil erosion compared to the control. EFP treatments also significantly improved the soil’s physical properties (bulk density, porosity, organic matter, aggregate stability). EFPs can diminish runoff and soil loss as the EFP-treated plots exhibited greater aggregate stability than the control. It was concluded that low EFP concentrations can improve soil hydrological properties and mitigate soil erosion. Further investigations are needed to optimize the EFP concentrations for different soil types.

Pesticide extraction from soil into runoff in North American and Australian croplands

Context Do some pesticides run off more than others? How does pesticide runoff vary with pesticide properties? Aims Improve understanding of pesticide runoff from croplands. Methods Concentrations in surface soil and in runoff from three Australian rainfall simulation studies and three rainfall simulation and five catchment studies in North American croplands were used. The ratio of event averaged runoff concentrations and the surface soil concentrations is the runoff extraction ratio. Key results Pesticide runoff concentrations were closely related to soil surface concentrations at the start of rainfall. Runoff extraction ratios were not significantly different for 13 pesticides with a wide range of properties, on gentle slopes (0–3%), but were significantly lower for three pesticides. On steeper slopes, runoff extraction was significantly greater for atrazine but lower for glyphosate and metolachlor. Low sloping, furrow irrigated fields had low sediment concentrations and low pesticide runoff concentrations for more tightly sorbed pesticides, but not for less sorbed pesticides. Runoff extraction was not significantly different for simulated and most catchment studies. Conclusions Similar runoff extraction ratios were due to similar hydrology and limited sediment concentrations. Different runoff extraction occurs on bare soil if (a) pesticides are leached from the runoff-mixing layer, requiring sorption coefficients less than two and significant infiltration, and no interflow, (b) sediment concentrations are either low (<2 g L−1) or high (>100 g L−1) and (c) pesticides have different concentration profiles in the runoff-mixing layer. Implications Conditions studied apply for croplands in the North American mid-west on silty soils and for Australian clay soils.

Overview of the research gaps in the rainfall simulator study

AbstractUrban flooding, soil erosion, and water pollution are common issues nowadays. The hydrological cycle is being disrupted due to improper planning of development that necessitates extensive studies conducted globally to study ways to address these issues. Significant and accurate data are required to rectify and amend the current situation. Rainfall simulators (RSs) are widely applied in research as they replicate the natural rainfall under controlled conditions and are repeatable. However, based on the published research, it is found that there are significant gaps. The RS has no standardization to cater different environmental conditions, yet vital rainfall characteristics and aspects have to be carried out wisely for better accuracy and data analysis. This review article discusses the gaps and parameters required in RS experiments.

Pesticide extraction from soil into runoff under a rainfall simulator

Context Runoff estimation is an important aspect of pesticide environmental behaviour and is the major loss pathway to the environment. Aims To improve understanding of pesticide runoff. Methods Data from three rainfall simulator studies was used. Twelve pesticides were studied ranged from tightly sorbed (DDE, soil sorption coefficient (KD) ~15 000 L kg−1) to weakly sorbed (dimethoate, KD < 30). Key results Event runoff pesticide concentrations were closely related to soil concentrations (0–25 mm depth). The ratio of runoff to soil concentration (the runoff extraction ratio, ERO), was similar for pesticides with a wide range of sorption and across the three soils: runoff concentration (μg L−1) = 28 × soil concentration (mg kg−1). ERO decreased with time after spraying, presumably due to lower concentrations in the top few mm of soil. Conclusions This model provides improved or similar estimates of pesticide runoff than previous models. Similar ERO values between sites was probably due to similar hydrology (high rainfall intensity, surface sealing, moist subsoils) and erosion, and because the same masses of soil and water are involved in mixing. Reduction in runoff concentrations by leaching was not influential, because infiltration was small and soil sorption too high. Implications Conditions studied apply during summer storms on most cotton and grain land on clay soils in the northern grain and cotton lands in eastern Australia. The model should be applicable under these conditions.

Effects of Selected Manure Sources on Runoff, Soil Loss, and Nutrient Transport

Highlights Surface water runoff was reduced following manure additions. Sediment yield was reduced following manure additions. Nutrient loss was increased following manure additions. Abstract. Soil erosion models are becoming increasingly accurate and now can simulate a variety of surface covers which can lessen erosion by reducing detachment and movement of soil particles. Currently, there is limited data on the effects of animal manure on soil erosion. Most process-based models credit animal manure as crop residue cover. Thus, there is a need for bench studies under laboratory conditions, as well as field studies to determine the effects manure applications have on runoff and sediment loss. Rainfall simulation studies were conducted to evaluate the influence of different animal manures on runoff, sediment yield, and nutrient loss using undisturbed soil monoliths placed in perforated trays. The soil was collected from fields managed under long-term no-till and a conventional till for over 15 years. Poultry litter, solid dairy manure, liquid swine manure, liquid dairy manure applied to the experimental units were compared to a no manure treatment. Generally, sediment yield and runoff amounts were reduced following manure application regardless of source (averaged across all rainfall events and manure rates), with reductions generally occurring with increasing rates of manure. When evaluating each rainfall event separately, runoff increased with increasing rates of manure for the liquid dairy manure only in the initial rainfall simulation events due to surface sealing. However, the effects of surface sealing decreased from the first rainfall simulation event to the third event. Sediment yield tended to be higher in conventional till versus no-till (only evaluated with liquid dairy manure); however, the addition of manure tended to be more effective at reducing sediment loss with conventional till. Dissolved reactive P, NH4-N, and NO3-N levels in the runoff effluent increased for all of the manure sources with increasing rates of manure. These results suggest that manure applications can reduce soil loss, especially from the conventionally-tilled treatment. Keywords: Manure, Rainfall simulation, Runoff, Soil erosion.

Per- and Poly-Fluoroalkyl Substances in Runoff and Leaching from AFFF-Contaminated Soils: a Rainfall Simulation Study.

The mobilization and transport of per- and poly-fluoroalkyl substances (PFASs) via surface runoff (runoff) from aqueous film-forming foam (AFFF)-contaminated soils during rainfall, flooding, or irrigation has not been thoroughly evaluated, and the effectiveness of carbonaceous sorbents in limiting PFASs in runoff is similarly unquantified. Here, laboratory-scale rainfall simulations evaluate PFAS losses in runoff and in leaching to groundwater (leachate) from AFFF-contaminated soils varying in texture, PFAS composition and concentration, and remediation treatment. Leaching dominated PFAS losses in soils with a concentration of ∑PFAS = 0.2-2 mg/kg. However, with higher soil PFAS concentrations (∑PFAS = 31 mg/kg), leachate volumes were negligible and runoff dominated losses. The concentration and variety of PFASs were far greater in leachates regardless of the initial concentrations in soil. Losses of PFASs were dependent on the C-chain length for leachates and more on the initial concentration in soil for runoff. Suspended materials did not meaningfully contribute to runoff losses. While concentrations of most PFASs declined significantly after the first rainfall event, desorption and transport in both runoff and leachates persisted over several rainfall events. Finally, results showed that sorption to AC mostly occurred during, not prior to, rainfall events and that 1% w/w AC substantially reduced losses in runoff and leachates from all soils.

Water retention and infiltration affected by conventional and conservational tillage on a maize plot; rainfall simulator and infiltrometer comparison study

Tillage practices have a profound influence on the propensity for overland flow formation. The hydrological behavior of nine experimental plots was investigated by means of saturated hydraulic conductivity (Ks) and water retention analysis provided by single-ring infiltrometer (INF) and rainfall simulator (RS) infiltration measurements. The applied management practices encompassed no-tillage, reduced tillage and several forms of conventional tillage methods. Specifically, the influence of wide and narrow sowing rows and the use of cover crops were examined. Finally, the applicability of INF and RS for overland flow formation evaluation on cropped plots was compared. The reduced tillage practices resulted in the Ks and water retention increase, implying a lower propensity for overland flow formation. The Ks in the reduced tillage plots were higher by 30–50% compared to conventionally tilled and by 20% compared to no-tilled plots, respectively. The differences in water retention were less straightforward as the reduced tilled plots exhibited higher retention than conventionally tilled plots (by >20%) but lower values compared to no-tilled plots in June (by 15%). The utilization of narrow sowing rows generally resulted in higher Ks and enhanced water retention compared to wide rows. The use of cover crops in the conventionally tilled plots led to a 40% increase in Ks and a 90% increase in water retention. Hence, the use of reduced tillage, narrow sowing rows or cover crops in the conventionally tilled plots were found desirable for the mitigation of soil erosion, flash flood occurrence and sufficient groundwater recharge. Eight times higher variance of Ks using a single-ring infiltrometer compared to RS indicated the incomparability of these two methods. Therefore, the RS should be considered as a benchmark for evaluating the propensity to overland flow formation on cropped plots.

Christiansen uniformity revisited: Re-thinking uniformity assessment in rainfall simulator studies

Rainfall simulators have been used extensively for a variety of research applications. The uniformity and spatial distribution of simulated rainfall is an important metric to consider when conducting rainfall simulator experiments. Over the past 80 years, several methods of assessing rainfall distribution and uniformity over the plot surface below a rainfall simulator have been developed. However, the Christiansen Uniformity Coefficient (CU; Christiansen, 1942) is most frequently used. Here, we provide a critique of this established methodology and metric for quantifying rainfall distribution characteristics. Uniformity coefficients express the distribution of rainfall across the plot surface as a single percentage value. Therefore, if all collection beakers receive equal volumes of water during an experimental run, the rainfall simulator or irrigation system would be applying water with 100% uniformity. There are shortcomings with using a single percentage value to represent rainfall simulator rainfall distribution, especially over a larger plot surface, and CU is highly dependent on the sampling methodology employed. This paper assesses rainfall uniformity by conducting a series of controlled uniformity experiments and resampling different grid layouts of collection containers. Results demonstrate that the coarseness of the sampling methodology affects rainfall uniformity coefficient values. CU values of 45 – 51% were recorded under a dense (17 × 17) sampling grid layout, compared to CU values of 81% using a coarser (8 × 8) sampling methodology, despite being subjected to comparable rainfall events. This paper explores the sensitivity of CU to the resolution and spatial layout of the sampling methodology used and assesses whether the CU captures repeatability and localised variability of uniformity between experimental runs. A complementary statistical approach expressing variations in relation to their standard deviation from the mean is presented. Understanding how experimental setup (i.e. number, density, spatial configuration of collection containers) affects CU is critical when interpreting results from different rainfall simulator studies and an understanding of the factors which influence CU is critical to benchmark the results of uniformity testing across different rainfall simulator setups.

Assessing runoff and erosion on woodland‐encroached sagebrush steppe using the Rangeland Hydrology and Erosion Model

AbstractThe transition of sagebrush‐dominated (Artemisia spp.) shrublands to pinyon (Pinus spp.) and juniper (Juniperus spp.) woodlands markedly alters resource‐conserving vegetation structure typical of these landscapes. Land managers and scientists in the western United States need knowledge and predictive tools for assessment and effective targeting of tree‐removal treatments to conserve or restore sagebrush vegetation and associated hydrologic function. This study developed modeling approaches to quantify the hydrologic vulnerability and erosion potential of sagebrush rangelands in the later stages of woodland encroachment and in response to commonly applied tree‐removal treatments. Using experimental data from multiple sites in the Great Basin Region, USA, and process‐based knowledge from decade‐long vegetation and rainfall simulation studies at those sites, we (1) assessed the capability of the Rangeland Hydrology and Erosion Model (RHEM) to accurately predict patch‐scale (12 m2) measured runoff and erosion from tree canopy and intercanopy hydrologic functional units in untreated and burned woodlands 9 years postfire, and (2) developed and evaluated multiple RHEM approaches/frameworks to model aggregated effects of tree canopy and intercanopy areas on patch‐ and hillslope‐scale (50 m length) runoff and erosion processes in untreated and treated (burned, cut, and masticated) woodlands. The RHEM accurately predicted measured runoff and sediment yield from patch‐scale rainfall simulations as partitioned on untreated and treated tree canopy and intercanopy areas and effectively parameterized the dominant controls on runoff and erosion process in woodlands. With few exceptions, evaluated hillslope‐scale RHEM frameworks similarly predicted reduced hydrologic vulnerability and erosion potential for conditions 9 years following tree removal by burning, cutting, and mastication treatments. Regressions of RHEM‐predicted hillslope runoff, sediment, and hydraulic/erosion parameters with bare ground and ground cover attributes indicate all RHEM frameworks effectively represented the dominant controls on hydrologic and erosion processes for rangelands and woodlands. The results provide RHEM frameworks and recommendations for assessing hydrologic vulnerability and erosion potential on woodland‐encroached sites and predicting the effectiveness of tree removal to reestablish a water and soil resource‐conserving vegetation structure on sagebrush rangelands. We anticipate our RHEM or similar modeling approaches may be applicable to analogous water‐limited landscapes elsewhere subject to woody plant encroachment.

Cover Image, Volume 51, Issue 2

Dr. Rory Maguire and Dr. Sheldon Hilaire hammer in steel frame for a field plot at Kentland Farm Research Station in preparation for rainfall simulation studies See S.S. Hilaire et al., “Culturable antibiotic‐resistant fecal coliform bacteria in soil and surface runoff after liquid dairy manure surface application and subsurface injection,” https://doi.org/10.1002/jeq2.20332. Photo by Jesse Radolinski. image

The importance of incorporating rain intensity profiles in rainfall simulation studies of infiltration, runoff production, soil erosion, and related landsurface processes

The temporal sequence of fluctuating rainfall intensities during an event - the intensity profile or 'rainfall pattern' - is known to affect water partitioning at the ground surface and associated erosional processes. There can be large differences in runoff ratios and runoff rates between early-peak and late-peak events, and hence in the depth, speed, and sediment transport capacity of resulting overland flow. Whilst rainfall intensity may fluctuate continually during all IPs in natural rainfall, there is little information on the rates of such intensity fluctuations that can be used to guide the design of rainfall simulation experiments. This review analyses relevant data derived from published high-resolution rainfall records and also from new analyses of data from Australian ground observing stations. Both sources confirm the occurrence of rates of intensity change of greater than 500 mm h−1 min−1. It is suggested that the fluctuating intensities characteristic of natural rainfall need to be employed in rainfall simulation experiments in order to generate results applicable to natural landsurface processes like infiltration or soil removal. Constant-intensity rain, as commonly used in rainfall simulation experiments, lacks both the kinds of rapid intensity fluctuations seen in natural rainfall, as well as any representation of natural intensity profiles. These unrepresentative conditions can result in lower runoff rates and larger proportions of infiltration than when intensity fluctuations are present. There is thus a strong case for changing the design of rainfall simulation to reflect more closely natural intensity fluctuations and intensity profiles and their influence on key surface processes such as overland flow and soil erosion.

Estrogenicity of agricultural runoff: A rainfall simulation study of worst-case scenarios using fresh layer and roaster litter, and farrowing swine manure

Scientists have correlated land application of animal wastes as fertilizer with the feminization of fish. Two questions were asked. 1) Under a worst case scenario when animal waste (layer and roaster litter, or farrowing swine slurry) is applied and tilled in 24 h prior to a surface-runoff producing rainfall, will estrogenic equivalents exceed the Lowest Observable Effect Concentration (LOEC) for fish (10 ng/L)? 2) Can calcium concentrations in runoff, measured using a rapid meter-based method, be used as a sentinel of elevated estrogenic activity? In a 3-yr study wastes were surface-applied and incorporated and 24 h later, 1.5 by 3 m plots were subjected to simulated rainfall and again 1 wk. and 3 wk. later. Nutrients in runoff were also measured, and in year 1 total coliforms and E. coli. were assessed. Except for an initial preliminary test run, runoff from all plots and years never exceeded 10 ng/L E2Eq equivalent. Calcium concentrations in runoff were not related to estrogenicity, negating its use as a sentinel marker. Specific estrogens in animal waste and runoff were identified by mass spectrometry with concentrations in runoff dependant on manure source and timing of rainfall. As expected, total coliform and E. coli concentrations in runoff were increased by the application of layer litter. Concentrations of nutrients in runoff would not be expected to result in surface water concentrations higher than guidelines for protection of aquatic species. Animal wastes applied in quantities appropriate for crop nutrient requirements, tilled into the soil surface, in observance of regulations avoiding application within 24 h of a predicted rain event, should not result in estrogen levels of environmental concern.

Rare earth oxide tracking coupled with 3D soil surface modelling: an opportunity to study small-scale soil redistribution

PurposeSmall-scale runoff and soil redistribution processes are important factors in rainfall simulation studies. Therefore, the main objective of this study is to examine the feasibility of rare earth oxide (REO) tracking combined with 3D surface modelling and soil crust analysis by scanning electron microscopy.Materials and methodsFour 40 mmh−1 rainfall simulations (divided into two blocks) were conducted on a Luvisol sample at 9% slope steepness. In a block, two successive simulations were run on a tilled, and then, on a crusted surface. Before the first rainfall simulation of a block, the tilled surface was prepared by hoeing and application of four REO tracers (Pr6O11 Sm2O3, Ho2O3 and Yb2O3) to the freshly tilled surface. REOs divided the parcel into two back, and two front sub-parcels. The REO runoff content was measured by XRF, while the redistributed REOs were measured by SEM on polished crust samples taken after the second experiment in each block. Additionally, before and after 3D models of the surface were created for determining runoff direction and redistribution pattern.Results and discussionAccording to the REO content of the soil loss samples, the soil washed down from the front sub-parcels, while back parcels started contributing to soil loss only during the second block experiments. The surface microtopography changed between the experiments. The runoff path from the back sub-parcels headed to one side of the parcel. This strong, cross-side runoff pattern explained the lack of the back sub-parcel REOs in the soil loss. Meanwhile, in the crust samples, several forms of the redistribution were identified. The REOs of the back sub-parcels were found in the samples that were collected in runoff paths, and the leaching pattern became traceable with REOs. Moreover, we were able to reconstruct the original surface easily on SEM images.ConclusionsSmall-scale redistribution and the role of the microtopography of the surface should be considered as an erosional factor in erosion studies in a more detailed way. Behaviour of the REO as a soil sediment tracer has great potential, although questions remain. REO tracing applied with runoff direction modelling and SEM analysis of soil crust samples was suitable to monitor the runoff path, and explain the soil redistribution pattern horizontally and vertically.

Salt Balance of Moderately Saline-Alkaline Rangeland Soil and Runoff Water Quality from Rainfall Simulation Studies near Moab, Utah U.S.A.

Salt Balance of Moderately Saline-Alkaline Rangeland Soil and Runoff Water Quality from Rainfall Simulation Studies near Moab, Utah U.S.A.

Effect of Broiler Litter Application Method on Metal Runoff from Pastures

Loss of metals from agricultural fields to surface water bodies causes deterioration of surface water quality. Method of application of broiler litter can affect loss of metals in surface runoff. Subsurface banding of broiler litter can decrease loss of P and N in surface runoff relative to surface application of broiler litter. However, limited research has been done to evaluate the impact of litter application method on loss of metals in surface runoff. Therefore, the objective of this research was to quantify differences in loss of metals in surface runoff from a tall fescue pasture as a function of method of application of broiler litter (i.e., surface vs. subsurface application). A rainfall simulation study was conducted in the Sand Mountain region of north Alabama. Results indicate that concentration and loadings of Cu, K, Mg, and Zn decreased in surface runoff as a result of application of broiler litter in subsurface bands and were similar between the subsurface‐banded broiler litter and control (no litter applied) treatments. Greater than 90% of the applied rainfall infiltrated, indicating that losses of metals via lateral and subsurface flows can be substantial. Overall, results of this study show that application of broiler litter in subsurface bands can reduce loss of metals in surface runoff. Future research studies should investigate the impact of method of application of broiler litter on the metal losses in leachate and subsurface flows.Core Ideas Broiler litter application method affects loss of metals in runoff. Subsurface banding of broiler litter reduced concentrations of metals in runoff. Loss of metals via lateral flow pathways could be significant in this region.

Effects of adding biochar of different particle sizes on hydro-erosional processes in small scale laboratory rainfall experiments on cultivated loessial soil

Adding biochar to soil is an efficient method to improve soil physicochemical properties. Understanding the effect of this method on soil and water loss is also important. However, there is insufficient data available to assess this effect. Thus, a simulated rainfall (intensity 90 mm h−1) study was conducted to explore the effect of biochar particle sizes (2–1, 1–0.25, and <0.25 mm) and incubation times (0 and 8 months) of biochar and soil mixture on soil and water loss. Our experiments consisted of measuring soil loss, surface runoff, >2 mm water-stable soil aggregate content, and soil saturated hydraulic conductivity (Ksat) from a perforated box (1 m long and 0.4 m wide) with a 27% slope gradient that contained soil, with a constant application rate of biochar at 1% (wt/wt). Soil without biochar was used as the control. The results indicated that biochar-treated soil delayed the time to runoff compared to the control by 12.67% to 32.58%, with the smallest particle size (<0.25 mm) and 8 months incubation being the most effective. In general, all tested biochar particle sizes had some control on soil and water loss. The total runoff volume after biochar additions of 2–1, 1–0.25, and <0.25 mm particle sizes decreased by 2.04%, 24.21%, and 29.63% and by 14.72%, 13.83%, and 30.76% with no incubation and 8 months of incubation, respectively, while the total erosion decreased by 12.86%, 34.30%, and 34.29% and by 20.41%, 11.85%, and 31.93% with no incubation and 8 months of incubation, respectively, compared to the control. Eight months of incubation could effectively decrease both the total runoff and amount of erosion only for soil amended with 2–1 mm biochar particles compared to those with no incubation. Furthermore, 2–1, 1–0.25, and <0.25 mm biochar treatments could increase >2 mm water-stable soil aggregate content and Ksat relative to the control. We speculated that the positive effects of biochar on soil and water loss were possibly due to an improvement in soil physical properties, such as an increase in the >2 mm water-stable soil aggregate and Ksat.

Impact of Flue Gas Desulfurization Gypsum and Manure Application on Transfer of Potentially Toxic Elements to Plants, Soil, and Runoff.

There are concerns regarding the fate of nutrients from surface application of animal manure. One approach to reduce losses of P is to treat manure with industrial byproducts such as flue gas desulfurization (FGD) gypsum. However, concerns regarding potentially toxic elements contributed to the environment have arisen based on previous element-rich forms of FGD gypsum that included fly ash, whereas "new" FGD gypsum without fly ash is much lower in contaminants. This study examined the impact of FGD gypsum application on soil, plants, and runoff when applied alone or with poultry litter (PL) to soil. The study consisted of a plant response study (four rates of FGD gypsum of 0, 2.2, 4.4, and 8.9 Mg ha and four rates of PL of 0, 4.4, 8.9, and 13.4 Mg ha) and a rainfall simulation study (3.4 Mg PL ha with four rates of FGD gypsum of 0, 2.2, 4.4, and 8.9 Mg ha and controls). Plant, soil, and runoff samples were analyzed for As, Ba, Be, Ca, Cd, Ba, Co, Cr, Cu, Fe, K, Mg, Mn, Na, Ni, P, Pb, Sb, Se, Tl, V, and Zn. Results indicated that FGD gypsum application would not result in increased potentially toxic elements in plants, soil, or runoff. In addition, the application of FGD gypsum significantly reduced P, As, and Fe concentrations in runoff, indicating that FGD gypsum can reduce the negative impact of manure surface application on surface water degradation.

Phosphorus Leaching from an Organic and a Mineral Arable Soil in a Rainfall Simulation Study.

Phosphorus derived from agricultural systems has been found to cause eutrophication of surface waters. To combat this, the specific location of soil profile P release is necessary for development of effective mitigation strategies. This paper describes a P leaching study of two Swedish arable soils, an organic (Typic Haplosaprist) and a mineral soil (Typic Hapludalf), both with high P content. Undisturbed soil columns isolated 0- to 20-, 20- to 40-, 40- to 60-, and 60- to 80-cm depth intervals. These were placed in a rainfall simulator and subjected to four 50-mm rainfall events to identify the origin of P leachate as a function of soil depth interval and physicochemical properties. Phosphorus losses were greatest from the two uppermost layers of both soils after 200 mm of artificial rainfall was applied at 5 mm h. Total P concentration in leachate from the 0- to 20-cm layer ranged from 2.1 to 8.8 mg L for the mineral and 3.7 to 10.3 mg L from the organic soil, with most (95-100%) in dissolved reactive P form. Degree of P saturation correlated well with total P leaching losses from the organic soil ( = 0.84) but not the mineral soil ( = 0.69), suggesting that the presence of Al and Fe (hydr)oxides has a stronger influence on P leaching in the organic soil. Results indicate that both soils have the potential to contribute concentrations of P above those known to cause eutrophication of surface waters.