Aluminum-based water treatment residual use in a constructed wetland for capturing urban runoff phosphorus: Column study

Aluminum-based water treatment residuals (Al-WTR) have a strong affinity to sorb phosphorus. In a proof-of-concept greenhouse column study, Al-WTR was surface-applied at 0, 62, 124, and 248 Mg/ha to 15 cm of soil on top of 46 cm of sand; Al-WTR rates were estimated to capture 0, 10, 20, and 40 years of phosphorus from an urban watershed entering an engineered wetland in Boise, Idaho, USA. Creeping red fescue (Festuca rubra) was established in all columns; one set of columns received no Al-WTR or plants. After plant establishment, once per week over a 12-week period, ~1.0 pore volumes of ~0.20 mg phosphorus/L was added to each column. Infiltration rates were measured, leachate was collected and analyzed for soluble phosphorus, and fescue yield, phosphorus concentration and uptake were determined. After plant harvest the sand, soil, and the Al-WTR layer were collected and analyzed for Olsen phosphorus, amorphous aluminum, iron, and phosphorus storage capacity (PSC), and soluble+aluminum+iron-bound, occluded, and calcium-bound phosphorus phases. Infiltration rate increased only due to the presence of plants. Leached phosphorus decreased (50%) with plants present; Al-WTR further reduced soluble phosphorus leaching losses (60%). Fescue yield, phosphorus concentration and uptake increased with increasing Al-WTR rate, due to Al-WTR sorbing and potentially making phosphorus more plant available; Olsen-extractable phosphorus increased with increasing Al-WTR rate, supporting this contention. The PSC was reduced with the 62 Mg/ha Al-WTR rate but maintained with greater Al-WTR rates. The 124 and 248 Mg/ha Al-WTR rates also contained greater phosphorus associated with the soluble+aluminum+iron and occluded phases which should be stable over the long-term (e.g., decadal). It was recommended to apply Al-WTR near the 124 and 248 Mg/ha rates in the future to capture urban runoff soluble phosphorus in the Boise, Idaho engineered wetland

Copper Sequestration Using Local Waste Products

Dairies utilize copper sulfate (CuSO4) foot baths to control hoof infections. Typical solutions are 5 or 10% CuSO4 (pH ~6), equal to 12,500 or 25,000 ppm Cu, respectively. When spent, hoof bath solutions are usually disposed of in waste lagoons and subsequently utilized for irrigation. In the Magic Valley, this practice appears to be causing soil Cu concentrations to increase. The goal of our research was to use local waste products to sequester Cu from a simulated hoof bath solution and to use waste products to adsorb excessive Cu from Cu-affected soils

Copper Sequestration Using Local Waste Products

Dairies utilize copper sulfate (CuSO4) foot baths to control hoof infections. Typical solutions are 5 or 10% CuSO4 (pH ~6), equal to 12,500 or 25,000 ppm Cu, respectively. When spent, hoof bath solutions are usually disposed of in waste lagoons and subsequently utilized for irrigation. In the Magic Valley, this practice appears to be causing soil Cu concentrations to increase. The goal of our research was to use local waste products to sequester Cu from a simulated hoof bath solution and to use waste products to adsorb excessive Cu from Cu-affected soils. We utilized lime waste and fly ash from the Amalgamated Sugar Company, LLC (Twin Falls, ID) to identify Cu sorption maximum as a function of pH. In triplicate, solutions containing one gram of material and increasing Cu concentrations (0, 2500, 5000, 12500, 25000 ppm Cu) were shaken for one month buffered at either pH 6, 7, 8, or 9. Materials shaken at pH 6 adsorbed the greatest amount of Cu, but concentrations up to 25000 ppm did not maximize all adsorption sites. Thus, additional solutions containing waste materials and Cu concentrations of 75000 and 100000 ppm Cu were shaken for one month at pH 6. Results showed that at pH 6 lime waste and fly ash adsorbed a maximum of ~ 45000 and 26000 ppm of Cu. The use of lime waste to sequester Cu from spent dairy CuSO4 hoof baths appears to be a viable option. Because lime waste adsorbed a greater quantity of Cu as compared to fly ash, we investigated the ability of lime waste to sequester Cu from Cu-affected soils. A soil from the Logan Soil Series (Typic Calciaquoll; pH 8.0; CEC = 14 meq/100g; % lime = 50%) which had received 0, 250, 500, or 1000 ppm Cu approximately one year earlier was utilized. Using a completely randomized design with four replicates, lime waste was applied at 0, 0.5, 1, and 2% by weight (~0, 10, 20, and 40 tons/acre), thoroughly incorporated, and allowed to incubate at 90% of field capacity for 3 months, after which 15 alfalfa (Medicago sativa L.) seeds were planted in each pot. Plants were allowed to grow for 2.5 months, and then were harvested at ½” above the soil surface, oven dried at 60oC for 72 hours, ground, weighed, and analyzed for total Cu content. Soils were air-dried, ground to pass a 1/16” screen, and then diethylenetriaminepentaacetic acid (DTPA; a measure of plant-availability) extractable Cu was measured. Soils were also subjected to a sequential metal extraction procedure which identified Cu associated with a) soluble species, carbonates, and cation exchange sites, b) iron and manganese oxyhydroxides, c) organic matter and sulfides, and d) residual phases. Increasing soil Cu application rate decreased alfalfa yield, but increasing lime waste application rate had no effect on improving alfalfa yield. Increasing soil Cu application also increased plant Cu concentration, while increasing lime application rate caused a decrease in plant Cu concentration. Increasing soil Cu application increased DTPA extractable Cu content, while increasing lime application rate did not affect extractable soil Cu content. Increasing Cu application rate increased Cu bound in all soil phases. Lime waste significantly affected Cu associated with most soil metal phases, but the changes were not large enough to help decrease soil Cu concentrations to below levels that would affect alfalfa growth and Cu accumulation. The use of lime waste to sequester Cu from Cu-affected soils, unlike from solution, does not appear to be a viable treatment process. Results of these studies will be published in a peer reviewed journal later this year

Assessment of Phosphorus Retention in Irrigation Laterals

Irrigation laterals transport irrigation return flow, including water, sediment, and dissolved nutrients, such as phosphorus (P), back to surface water bodies. Phosphorus transformations during transport can affect both P bioavailability and the best management practices selected to minimize P inputs to waters of the United States. The objective of this study was to determine P retention in three irrigation laterals. Soluble reactive P (SRP) concentrations in lateral waters were increased from 0.08 to 0.25 mg L -1 (0.08 to 0.25 ppm) by constantly injecting a phosphate (PO4) solution for 2.5 hours. Bromide (Br) was used as a conservative tracer to determine dilution effects. Water was sampled at 10-minute intervals, beginning 30 minutes prior to injection and 120 minutes following injection, at one upstream location and various downstream locations to approximately 1,550 m (~1 mi) from injection sites. When at steady state, SRP concentrations only decreased by 5% over the lengths studied, equating to P uptake lengths of over 18 km (11.2 mi), which was one to two orders of magnitude greater than natural streams; the linear SRP uptake rate was 0.011 mg L -1 km -1 (0.018 ppm mi -1 ). Longer P uptake lengths and lower uptake rates in irrigation laterals, as compared to natural streams, may be due to the elevated sediment equilibrium P concentration, greater water velocities, and removal of vegetation causing a reduction in frictional resistance. Reducing water velocities should optimize irrigation lateral conditions to reduce uptake length and maximize P uptake

Clinoptilolite Zeolite Influence on Nitrogen in a Manure-Amended Sandy Agricultural Soil

Development of best management practices can help improve inorganic nitrogen (N) availability to plants and reduce nitrate-nitrogen (NO3-N) leaching in soils. This study was conducted to determine the influence of the zeolite mineral clinoptilolite (CL) additions on NO3-N and ammonium-nitrogen (NH4-N) in two common Pacific Northwest soils. The effects of CL application rate (up to 26.9 Mg ha-1) either band applied or mixed with a set rate of N fertilizer on masses of NO3-N and NH4-N in leachate and soil were investigated in a column study using a Portneuf silt loam (coarse-silty mixed mesic Durixerollic Caliciorthid) and a Wolverine sand (Mixed, frigid Xeric Torripsamment). All treatments for each soil received a uniform application of N from urea fertilizer, with fertilizer banded or mixed with CL. In the Portneuf soil, band application of CL and N contained 109% more total inorganic N (NO3-N + NH4-N) in the soil/leachate system compared with mixing. In both soils, CL application rate influenced the quantity of NO3-N and NH4-N in the leachate and soil. Application of CL at rates of 6.7 to 13.4 Mg ha-1 resulted in the conservation of inorganic N in the soils. Band applying CL and N seems to conserve available inorganic N in the soil compared with mixing CL and N possibly because of decreased rates of microbial immobilization, nitrification, and denitrification

Continuous biosolids application affects grain elemental concentrations in a dryland-wheat agroecosystem

Continuous land application of biosolids in a beneficial-use program changes trace-element availability to plants over time. Consequently, what regression model, if any, could best predict wheat (Triticum aestivum L.) grain concentrations in a biosolids-amended dryland agroecosystem? We calculated paraboloid, linear, quadratic, and exponential-rise-to-a maximum equations for grain Ba, Cd, Cu, Mn, Mo, Ni, P, and Zn concentration versus number of biosolids applications and/or soil NH4HCO3-dithethylenetriaminepentaacetic acid (AB-DTPA) extract concentrations for two sites that had each received six applications of Littleton/Englewood, CO, USA Wastewater Treatment Facility biosolids. The paraboloid-regression models were superior (higher R2 values, lower S.E. of the estimate) to other models. Soils classified the same as the Weld soil (used in this study) at the family level (fine, smectitic, mesic Aridic Argiustolls) encompass 25 soil series in 10 US states with an aerial extent of 2.3 × 106 ha. The paraboloid-regression model approach probably would be applicable to these similarly classified soils

Soil phosphorus availability differences between sprinkler and furrow irrigation

Water flowing in irrigation furrows detaches and transports soil particles and subsequently nutrients such as phosphorus. To reduce the risk of erosion and offsite phosphorus transport, producers in south-central Idaho have been converting from furrow to sprinkler irrigation. We completed research on soil phosphorus dynamics in furrow versus sprinkler irrigated soils from four paired-fields in the region. Surface soils (0-2.5 inches) were obtained from fields in September following barley harvest. Furrow irrigated soils contained 38 parts per million of plant-available phosphorus (i.e. Olsen-extractable), on average, as compared to 20 parts per million under sprinkler irrigation. These results are important as 20 parts per million extractable phosphorus can be construed as the point where soil phosphorus is considered low to medium in soil testing; extractable phosphorus values over 40 parts per million limit sites to phosphorus application based on crop uptake only. These soils were also analyzed using a sequential extraction technique, and total and amorphous iron were determined to identify inorganic phosphorus pools. Soils under furrow irrigation had greater concentrations of inorganic phosphorus in the soluble/aluminum-bound/iron-bound and occluded phases, and in the amorphous iron phase. Phosphorus concentrations in all other soil phases were similar between the two irrigation practices. Findings suggest that iron redox chemistry plays a large role in phosphorus release under furrow irrigation, even in aridic systems. In terms of soil phosphorus, results support the use of sprinkler irrigation as a best management and conservation practice

Biochar and Manure Affect Calcareous Soil and Corn Silage Nutrient Concentrations and Uptake.

When added to soils, carbon-rich biochar derived from the pyrolysis of woody materials can sequester atmospheric carbon dioxide, mitigate climate change, and potentially increase crop productivity. However, research is needed to confirm the suitability and sustainability of biochar application to different soils. We applied four treatments (dry wt.) to an irrigated calcareous soil in Nov. 2008: control; stockpiled dairy manure, 18.8 Mg/ha; hardwood-derived biochar, 22.4 Mg/ha; and manure + biochar using previous rates. Nitrogen fertilizer was applied when needed (based on pre-season soil test N and crop requirements) in all plots and years with N mineralized from added manure included in this determination. Available soil nutrients (NH4-N, NO3-N, Olsen P, diethylenetriaminepentaacetic acid (DTPA)-extractable K, Mg, Na, Cu, Mn, Zn, Fe), total C and N (TC, TN), total organic C (TOC), and pH were determined periodically, and silage corn nutrient concentration, yield, and uptake were measured over two growing seasons. Biochar treatment resulted in a 1.5-fold increase in available soil Mn and 1.4-fold increase in TC and TOC, where manure produced a 1.2- to 1.7-fold increase in soil macro- and micro-nutrients (except Fe), compared to controls. In 2009, biochar increased corn silage B concentration but produced no yield increase; and in 2010, biochar decreased corn silage TN (33%), S (7%) concentrations, and yield (36%) relative to controls. Manure produced a 1.3-fold increase in corn silage Cu, Mn, S, Mg, K, and TN concentrations and yield compared to the control in 2010. The combined biochar-manure effects were not synergistic, except in the case of available soil Mn. In these calcareous soils biochar did not alter pH or availability of P and cations, as is typically observed for acidic soils. If the second year results are indicative of future effects, they suggest that biochar applications lead to reduced N availability in calcareous soils and may need to be accompanied by additional N inputs if yield targets are to be maintained

Sulfate Foot Baths on Dairies and Crop Toxicities

A rising concern with the application of dairy wastes to agricultural fields is the accumulation of copper (Cu) in the soil. Copper sulfate (CuSO4) from cattle footbaths is washed out of dairy barns and into wastewater lagoons. The addition of CuSO4 baths can increase Cu concentration significantly in manure slurry, from approximately 5.0 grams per 1,000 liters to 90.0 grams per 1,000 liters. The Cu-enriched dairy waste is then applied to agricultural crops, thus raising concerns about how soils and plants are impacted by these Cu additions

Cross-linked polymers increase nutrient sorption in degraded soils

Cross-linked polymer hydrogels, such as polyacrylamide co-polymer (XPAM) or polyacrylate (XPAA), can alter soil chemistry and crop nutrient uptake but the persistence of these effects has been little studied. This 9-y, irrigated, outdoor pot study evaluated a single, one-time addition of XPAM or XPAA at 0.25% or 0.5% dry wt. (5.6 or 11.2 Mg ha-1) in a degraded calcareous silt loam. Controls included an unamended degraded soil and an unamended, non-degraded soil (i.e. topsoil). Soils were hand-tilled and planted to crops each year. We measured nutrients in soil and leachate water each year, and in the first 5 y, crop yields and nutrient uptake. Both hydrogels increased average soil pH and electrical conductivity (EC), soil extractable K, Na, and TOC, and decreased soil extractable Mg relative to the control. Unlike XPAM, XPAA produced a greater increase in soil extractable K, increased extractable Fe, Zn, Mn, and Cu, increased Olsen P, and decreased total inorganic C. Neither hydrogel affected crop yields but XPAA increased K and Zn and decreased Mg and Na uptake in crops compared to controls. Relative to the control, both hydrogels decreased cumulative Ca, Mg, and S leaching mass losses and increased mean EC of leachate. Unlike XPAM, XPAA increased cumulative leaching mass losses of K, P, NO3-N, and NH4-N relative to the control. The hydrogels’ soil effects persisted for greater than or equal to 7 years and their effect differed as a function of the quantity of included counterions and the stability of the gel structure after soil placement