Organic Waste Nitrogen and Phosphorus Dynamics Under Dryland Agroecosystems

Organic waste beneficial-use programs effectively recycle plant nutrients when applied at agronomic rates. Plant-nutrient availability, transport, and fate questions have arisen when organic wastes such as biosolids have been applied to dryland agroecosystems. What is the Nfertilizer equivalency of biosolids? What is the N mineralization rate of biosolids over periods of excess moisture or drought, and over long periods of time? Would biosolids, applied at an agronomic N rate for dryland winter wheat (Triticum aestivum L.), oversupply P? If overapplication occurred, what would the repercussions be in terms of excess soil P? Our objectives were to determine: biosolids N fertilizer equivalency; biosolids N mineralization during years of above and below average precipitation, and long-term N mineralization; which soil P phases dominate following years of biosolids application; and the potential increased environment risk of P when applying an agronomic N rate or excessive rate of biosolids. To address questions related to N dynamics, we utilized research results collected between 1993 and 2004 from a site in Eastern Colorado which received 0, 1, 2, 3, 4, and 5 dry tons biosolids A-1. To address questions related to P dynamics, results collected between 1982 and 2003 from a second Eastern Colorado site which received 0, 3, 6, 12, and 18 dry tons biosolids A-1 were used. During years of above-average and below-average precipitation, first-year biosolids N mineralization rates were estimated at 25-32% and 21-27%, respectively; long-term first-year mineralization rate ranged between 27-33%. Based on wheat-grain N uptake, we found that an application rate of 1 dry ton biosolids A-1 supplied about 20 lbs N A-1. Based on the Colorado P index risk assessment, biosolids applied at agronomic N rates would not force producers to alter application strategies. However, based on this risk assessment, biosolids over-application would force land application to be based on crop P requirements. Previous results showed a minimum of 3 cropping cycles were necessary to reduce soil P concentrations to levels considered less apt in causing environmental degradation. A future reduction in water availability may force some Idaho agricultural land to shift from irrigated to dryland conditions. And, coupled with the increased production of dairy waste, land applicators will need to find new means to protect natural resources under dryland conditions. Results from our studies can help improve nutrient use efficiency and minimize environmental risk associated with dryland organic waste land application

Fifteen Years of Wheat Yield, N Uptake, and Soil Nitrate-N Dynamics in a Biosolids-Amended Agroecosystem. Agriculture, Ecosystems and Environment

Understanding N dynamics in biosolids-amended agroecosystems can help avoid over-application and the potential for environmental degradation. We investigated 15-years of biosolids application to dryland-wheat, questioning what is the relationship between cumulative grain yield and N uptake (N removal) and biosolids or N fertilizer rates and how many times biosolids or N fertilizer are applied? How are wheat-grain production and N uptake intertwined with residual soil nitrate-N? We found that biosolids or N fertilizer rates plus the number of applications of each material produced planar-regression (3-dimensional) models with 15-years of grain yield and N uptake data (all R2 > 0.93). To evaluate how yield or N uptake impacted residual soil nitrate-N, we completed linear regressions on yield, N uptake, and soil nitrate-N. We then correlated the slopes where P<0.10 for the yield and soil nitrate-N and the N uptake and soil nitrate-N. A significant negative relationship was found for biosolids application for each of these comparisons while the N fertilizer results were inconsistent. For the biosolids treatments, as yield or N uptake increased, residual soil nitrate-N decreased. Our findings show that planar regression models could aid biosolids beneficial-use management programs when considering agroecosystem N dynamics

Drinking Water Treatment Residuals: A Reveiw of Recent Uses

Coagulants such as alum, [Al2(SO4)3X14H2O], ferric chloride [FeCl3], or ferric sulfate [Fe2(SO4)3] are commonly used to remove particulate and dissolved constituents from water supplies in the production of drinking water. The resulting waste product, called water-treatment residuals (WTR), contains precipitated Al and Fe oxyhydroxides resulting in a strong affinity for anionic species. Recent research has focused on using WTR as cost-effective materials to reduce soluble phosphorus (P) in soils, runoff, and land-applied organic wastes (manures and biosolids). Studies show P adsorption by WTR to be fast and nearly irreversible, suggesting long-term stable immobilization of WTR-bound P. Because excessive WTR application can induce P deficiency in crops, effective application rates and methods remain an area of intense research. Removal of other potential environmental contaminants [ClO4, Se(+IV and +VI), As(+III and +V), Hg] by WTR has been documented, suggesting potential use of WTRs in environmental remediation. While creation of Al plant toxicity and enhanced Al leaching are concerns expressed by researchers, at circumneutral soil pH conditions these effects are minimal. Radioactivity, trace element levels, and enhanced Mn leaching have also been cited as potential problems in WTR usage as a soil supplement. However, these issues can be managed so as not to limit the beneficial use of WTRs in controlling off-site P losses to sensitive water bodies or reducing soil-extractable P concentrations

Copper and zinc speciation in a biosolids-amended semiarid grassland soil

Predicting trace metal solid phase speciation changes associated with long-term biosolids land application is important for understanding and improving environmental quality. Biosolids were surface-applied (no incorporation; 0, 1, 2, 5, 10, and 15 tons per acre) to a semi-arid grassland in 1991 (single) or again in 2002 (repeated). In July 2003, soils were obtained from the 0-3, 3-6, and 6-12-inch depths in all plots. Using soil pH, soluble anion and cation concentrations from 0.01 moles per liter calcium chloride extractions, and dissolved organic carbon content, copper and zinc associated with minerals, hydrous ferric oxide, or dissolved organic phases was modeled using Visual Minteq. Scanning electron microscopy and energy dispersive x-ray analysis was also utilized to identify solid phase metal associations present in single and repeated biosolids-amended soils. Based on soil solution chemistry and verified using Visual Minteq, greater than 89 and 96 percent of copper and zinc, and greater than 99 percent of zinc were adsorbed to hydrous ferric oxides in all single or repeated biosolids-applied soils, respectively. However, when detected in the repeated biosolids treatments, only 59-79 percent of copper was adsorbed to hydrous ferric oxides while 21-41 percent was associated with dissolved organic carbon; downward copper movement was associated with dissolved organic carbon. The scanning electron microscopy and energy dispersive x-ray analysis of clay-sized separates from all soil depths led to direct observation of iron-zinc, aluminum-zinc, and aluminum-copper associations. Results implied that even after surface-applying biosolids either once or twice of up to 15 tons per acre, soil solution concentrations, Visual Minteq predictions, and scanning electron microscopy and energy dispersive x-ray analysis suggested minimal shifts occur in phases controlling long-term copper and zinc solubility

Infrequent Composted Biosolids Applications Affect Semi-arid Grassland Soils and Vegetation

Monitoring of repeated composted biosolids applications is necessary for improving beneficial reuse program management strategies, because materials will likely be reapplied to the same site at a future point in time. A field trial evaluated a single and a repeated composted biosolids application in terms of long-term (13–14 years) and short-term (2–3 years) effects, respectively, on soil chemistry and plant community in a Colorado semi-arid grassland. Six composted biosolids rates (0, 2.5, 5, 10, 21, 30 Mg ha?1) were surface applied in a split-plot design study with treatment (increasing compost rates) as the main factor and co-application time (1991, or 1991 and 2002) as the split factor applications. Short- and longterm treatment effects were evident in 2004 and 2005 for soil 0–8 cm depth pH, EC, NO3-N, NH4-N, total N, and AB-DTPA soil Cd, Cu, Mo, Zn, P, and Ba. Soil organic matter increases were still evident 13 and 14 years following composted biosolids application. The repeated composted biosolids application increased soil NO3-N and NH4-N and decreased AB-DTPA extractable Ba as compared to the single composted biosolids application in 2004; differences between short- and long-term applications were less evident in 2005. Increasing biosolids rates resulted in increased native perennial grass cover in 2005. Plant tissue Cu, Mo, Zn, and P concentrations increased, while Ba content decreased depending on specific plant species and year. Overall, the lack of many significant negative effects suggests that shortor long-term composted biosolids application at the rates studied did not adversely affect this semi-arid grassland ecosystem

Organic Waste Nitrogen and Phosphorus Dynamics Under Dryland Agroecosystems

Organic waste beneficial-use programs effectively recycle plant nutrients when applied at agronomic rates. Plant-nutrient availability, transport, and fate questions have arisen when organic wastes such as biosolids have been applied to dryland agroecosystems. What is the Nfertilizer equivalency of biosolids? What is the N mineralization rate of biosolids over periods of excess moisture or drought, and over long periods of time? Would biosolids, applied at an agronomic N rate for dryland winter wheat (Triticum aestivum L.), oversupply P? If overapplication occurred, what would the repercussions be in terms of excess soil P? Our objectives were to determine: biosolids N fertilizer equivalency; biosolids N mineralization during years of above and below average precipitation, and long-term N mineralization; which soil P phases dominate following years of biosolids application; and the potential increased environment risk of P when applying an agronomic N rate or excessive rate of biosolids. To address questions related to N dynamics, we utilized research results collected between 1993 and 2004 from a site in Eastern Colorado which received 0, 1, 2, 3, 4, and 5 dry tons biosolids A-1. To address questions related to P dynamics, results collected between 1982 and 2003 from a second Eastern Colorado site which received 0, 3, 6, 12, and 18 dry tons biosolids A-1 were used. During years of above-average and below-average precipitation, first-year biosolids N mineralization rates were estimated at 25-32% and 21-27%, respectively; long-term first-year mineralization rate ranged between 27-33%. Based on wheat-grain N uptake, we found that an application rate of 1 dry ton biosolids A-1 supplied about 20 lbs N A-1. Based on the Colorado P index risk assessment, biosolids applied at agronomic N rates would not force producers to alter application strategies. However, based on this risk assessment, biosolids over-application would force land application to be based on crop P requirements. Previous results showed a minimum of 3 cropping cycles were necessary to reduce soil P concentrations to levels considered less apt in causing environmental degradation. A future reduction in water availability may force some Idaho agricultural land to shift from irrigated to dryland conditions. And, coupled with the increased production of dairy waste, land applicators will need to find new means to protect natural resources under dryland conditions. Results from our studies can help improve nutrient use efficiency and minimize environmental risk associated with dryland organic waste land application

Drinking Water Treatment Residuals: A Reveiw of Recent Uses

Coagulants such as alum, [Al2(SO4)3X14H2O], ferric chloride [FeCl3], or ferric sulfate [Fe2(SO4)3] are commonly used to remove particulate and dissolved constituents from water supplies in the production of drinking water. The resulting waste product, called water-treatment residuals (WTR), contains precipitated Al and Fe oxyhydroxides resulting in a strong affinity for anionic species. Recent research has focused on using WTR as cost-effective materials to reduce soluble phosphorus (P) in soils, runoff, and land-applied organic wastes (manures and biosolids). Studies show P adsorption by WTR to be fast and nearly irreversible, suggesting long-term stable immobilization of WTR-bound P. Because excessive WTR application can induce P deficiency in crops, effective application rates and methods remain an area of intense research. Removal of other potential environmental contaminants [ClO4, Se(+IV and +VI), As(+III and +V), Hg] by WTR has been documented, suggesting potential use of WTRs in environmental remediation. While creation of Al plant toxicity and enhanced Al leaching are concerns expressed by researchers, at circumneutral soil pH conditions these effects are minimal. Radioactivity, trace element levels, and enhanced Mn leaching have also been cited as potential problems in WTR usage as a soil supplement. However, these issues can be managed so as not to limit the beneficial use of WTRs in controlling off-site P losses to sensitive water bodies or reducing soil-extractable P concentrations

Infrequent Composted Biosolids Applications Affect Semi-arid Grassland Soils and Vegetation

Monitoring of repeated composted biosolids applications is necessary for improving beneficial reuse program management strategies, because materials will likely be reapplied to the same site at a future point in time. A field trial evaluated a single and a repeated composted biosolids application in terms of long-term (13–14 years) and short-term (2–3 years) effects, respectively, on soil chemistry and plant community in a Colorado semi-arid grassland. Six composted biosolids rates (0, 2.5, 5, 10, 21, 30 Mg ha?1) were surface applied in a split-plot design study with treatment (increasing compost rates) as the main factor and co-application time (1991, or 1991 and 2002) as the split factor applications. Short- and longterm treatment effects were evident in 2004 and 2005 for soil 0–8 cm depth pH, EC, NO3-N, NH4-N, total N, and AB-DTPA soil Cd, Cu, Mo, Zn, P, and Ba. Soil organic matter increases were still evident 13 and 14 years following composted biosolids application. The repeated composted biosolids application increased soil NO3-N and NH4-N and decreased AB-DTPA extractable Ba as compared to the single composted biosolids application in 2004; differences between short- and long-term applications were less evident in 2005. Increasing biosolids rates resulted in increased native perennial grass cover in 2005. Plant tissue Cu, Mo, Zn, and P concentrations increased, while Ba content decreased depending on specific plant species and year. Overall, the lack of many significant negative effects suggests that shortor long-term composted biosolids application at the rates studied did not adversely affect this semi-arid grassland ecosystem

Biosolids Application to No-Till Dryland Agroecosytems

Dryland agroecosystems are generally ideal environments for recycling biosolids. However, what is the efficacy of biosolids addition to a no-till dryland management agroecosystem? From 2000 to 2010, we studied application of biosolids from the Littleton/Englewood, CO Wastewater Treatment Plant versus commercial nitrogen fertilizer in dryland no-till wheat (Triticum aestivum, L.)-fallow (WF) and wheat-corn (Zea mays, L.)-fallow (WCF) rotations at a site approximately 50 miles east of Denver, CO. We tested if biosolids would produce the same yields and grain phosphorus, zinc, and barium concentrations as an equivalent rate of nitrogen fertilizer, that biosolids-borne phosphorus, zinc, and barium would not migrate below the 4 inch soil depth, and that biosolids application would result in the same quantity of residual nitrate-nitrogen as the equivalent nitrogen fertilizer rate. Biosolids and nitrogen fertilizer produced similar wheat and corn yields; but, biosolids application resulted in smaller wheat grain barium due to the soil formation of barium sulfate. Biosolids application produced greater soil nitrate-nitrogen concentrations than nitrogen fertilizer in the 1 to 2 foot and 2 to 3 foot depths for the WF rotation and all but the 2 to 4 inch and the 4 to 5 foot depths for the WCF rotation. We concluded that biosolids application in a no-till managed dryland agroecosystem is an efficacious method of recycling this nutrient source