Olawale O. Oladeji

Efficacy of drinking-water treatment residual in controlling off-site phosphorus losses: a field study in Florida.

Land application of drinking-water treatment residuals (WTR) has been shown to control excess soil soluble P and can reduce off-site P losses to surface and ground water. To our knowledge, no field study has directly evaluated the impacts of land application of WTRs on ground water quality. We monitored the effects of three organic sources of P (poultry manure, Boca Raton biosolids, Pompano biosolids) or triple superphosphate co-applied with an aluminum-based WTR (Al-WTR) on soil and ground water P and Al concentrations under natural field conditions for 20 mo in a soil with limited P sorption capacity. The P sources were applied at two rates (based on P or nitrogen [N] requirement of bahiagrass) with or without Al-WTR amendment and replicated three times. Without WTR application, applied P sources increased surface soil soluble P concentrations regardless of the P source or application rate. Co-applying the P sources with Al-WTR prevented increases in surface soil soluble P concentrations and reduced P losses to shallow ground water. Total dissolved P and orthophosphate concentrations of shallow well ground water of the N-based treatments were greater (>0.9 and 0.3 mg L(-1), respectively) in the absence than in the presence ( approximately 0.6 and 0.2 mg L(-1), respectively) of Al-WTR. The P-based application rate did not increase ground water P concentrations relative to background concentrations. Notwithstanding, Al-WTR amendment decreased ground water P concentrations from soil receiving treatments with P-based application rates. Ground water total dissolved Al concentrations were unaffected by soil Al-WTR application. We conclude that, at least for the study period, Al-WTR can be safely used to reduce P leaching into ground water without increasing the Al concentration of ground water.

Land Application of Aluminum Water Treatment Residual: Aluminum Phytoavailability and Forage Yield

Negative impacts of land‐applied aluminum (Al)–rich water treatment residuals (WTRs), which have been suggested to improve soil phosphorus (P) sorption, could include excessive immobilization of plant‐available P and Al phytotoxicity. We studied the impacts of an Al‐rich WTRs on agronomic returns and plant Al concentrations in glasshouse and field studies. The glasshouse study was a 4 × 2 × 3 factorial experiment with one control in a randomized complete block design and three replicates. Four sources of P were each applied at two agronomic rate [44 kg P ha−1, P‐based rate; and 179 kg plant‐available nitrogen (PAN) ha−1, N‐based rate] to topsoil (0–15 cm) of a sandy, siliceous, hyperthermic Arenic Alaquods. Three WTR rates (0, 10, and 25 g kg−1 oven‐dry‐weight basis) were further applied, whereas the control received neither P source nor WTRs. Bahiagrass (Paspalum notatum Fluggae), ryegrass (Lolium perenne L.), and a second bahiagrass crop were continuously grown in succession for 18 months. Applied WTRs increased soil Al but not plant Al concentrations (22–80 mg Al kg−1), which fell within the normal concentration range for pasture plants. In the glasshouse, when WTRs were incorporated with the soil, bahiagrass dry matter (DM) accumulation was reduced, but ryegrass DM was not affected even at 25 g kg−1 WTR. A 2‐year field study, with same treatments but two rates of WTRs (0 and 10 g kg−1 WTR) surface applied to established bahiagrass on the same soil type (Spodosols) showed neither reduced yields nor increased plant Al phytoavailability in the WTR treatments. The studies show no increase in plant Al is associated with Al‐WTRs applied to reduce excess soil‐soluble P and P losses but plant DM accumulation may be reduced.

Drinking‐Water Treatment Residual Effects on the Phosphorus Status of Field Soils Amended with Biosolids, Manure, and Fertilizer

Abstract Concerns about surface water pollution with phosphorus (P) from biosolids and manures are prompting land application guidelines that limit residual application rates to those based on crop‐P removals (typically, no more than 2 Mg ha−1). Such rates are so low that the beneficial recycling of residuals is seriously threatened. Greater application rates [i.e., nitrogen (N) based] require judicious selection of residuals (low soluble P contents) and/or soil amendments, such as drinking‐water treatment residuals (WTRs) to control soluble P concentration. Although in the short term, WTR is effective in reducing soluble P levels, field studies to evaluate the stability of WTR‐immobilized P are scarce. The initial objective of this study was to determine the effects of WTR on P losses to surface and groundwater from Florida sand amended with different P sources (biosolids, manure, and inorganic fertilizer) applied at P‐ and N‐based rates. However, this objective could not be pursued to its logical conclusion because of severe flooding of the field 17 months after amendment application. The flooding appears to have compromised the treatments (moved soil and associated amendments across plots), which forced early termination of the experiment. Measurements taken after the flooding, however, provided a unique opportunity to assess the usefulness of WTR in controlling P solubility following severe flooding of WTR‐amended plots. Soluble P values measured from WTR‐amended A horizon plots were significantly lower than the plots without WTR amendment throughout the study. Phosphorus‐specific measurements in the Bh horizon suggest that excessive P leaching apparently occurred in the plots without WTR amendment and the control plots, whereas very little or no P leaching occurred in the WTR‐amended plots. Thus, despite extensive hurricane‐induced flooding of the fields, the WTR was able immobilize P and prevent excessive P leaching. We conclude that WTR could reduce offsite P transport, which will lower P loads into nutrient‐sensitive surface water systems, and that WTR‐immobilized P is stable even under severe flooding conditions.

Relative Phosphorus Phytoavailability of Different Phosphorus Sources

Understanding differences in the phytoavailability of various phosphorus (P) sources should improve matching P additions to plant needs and minimize excessive buildup of bioavailable P, which can degrade aquatic systems. We evaluated relative P phytoavailability (RPP) of different P sources in glasshouse and field studies. Bahiagrass (Paspalum notatum Fluggae), ryegrass (Lolium perenne L.), and a second bahiagrass crop were grown in succession in a P‐deficient soil amended with four sources of P (triple superphosphate (TSP), Boca Raton and Pompano; biosolids, and poultry manure), each applied at two rates in the glasshouse study and to an established bahiagrass pasture in the field. The RPP values estimated from plant P uptake of each organic source of P relative to TSP in the glasshouse were similar for the three croppings and similar to the estimates derived from the field study, but varied for the different P sources. Values ranged from 30% for poultry manure to 85% for Boca Raton biosolids. Boca Raton biosolid P was as readily available as P in TSP and would be classified as a high RPP (>75% RPP) source, but Pompano biosolids and manure would be classified as moderate RPP materials (25–75% RPP). The RPP values observed in manure and Pompano biosolid treatments are consistent with 50% “effectiveness” suggested for biosolid P in U.S. Environmental Protection Agency (USEPA) guidelines, whereas P bioavailability of Boca Raton biosolids is similar to mineral fertilizer.

Effect of Long-Term Application of Biosolids for Mine Land Reclamation on Groundwater Chemistry: Nutrients and Other Selected Qualities

Leaching of nitrogen (N) and phosphorus (P) to groundwater can limit the land application of fertilizer, biosolids, and other soil amendments. Groundwater quality monitoring data collected over a 34-yr period at a 1790-ha site in Fulton County, Illinois, where strip-mined land was reclaimed with biosolids, were used to evaluate long-term impacts of biosolids on groundwater N, P, and other parameters. Seven strip-mined fields repeatedly treated with biosolids at 801 to 1815 Mg ha cumulative rate (equivalent to 24-55 dry Mg ha yr) between 1972 and 2004 were compared with another seven fields treated annually with chemical fertilizer at agronomic rates. Groundwater from wells installed in each of the fields and two public wells that served as background (reference) were sampled for 35 yr, monthly between 1972 and 1986 and quarterly between 1987 and 2006. Data show greater chloride (Cl), sulfate (SO) and electrical conductivity (EC) of groundwater from wells in biosolids fields than those in fertilizer fields. Also, groundwater nitrate N (NO-N) concentrations were greater in biosolids-amended fields than in fertilizer fields, but below regulatory limit of 10 mg L in Illinois Part 620 regulation. Conversely, groundwater P concentrations were consistently lower in biosolids than in chemical fertilizer wells throughout the 35-yr monitoring period. The study demonstrates that the repeated application of biosolids, even at higher than agronomic rate, would cause only minor nitrate increase and no P increase in groundwater.

Effects of long-term application of biosolids for mine land reclamation on groundwater chemistry: trace metals.

Data collected for 35 yr from a 1790-ha strip mine reclamation site in Fulton County, Illinois, where biosolids were applied from 1972 to 2004, were used to evaluate the impacts of long-term biosolids application on metal concentrations in groundwater. Groundwater samples were collected between 1972 and 2006 from wells installed in seven strip-mined fields treated with biosolids at cumulative loading rates of 801 to 1815 dry Mg ha and from another seven fields (also strip mined) treated with mineral fertilizer. Samples were collected monthly between 1972 and 1986 and quarterly between 1987 and 2004 and were analyzed for total metals. The concentrations of metals in groundwater were generally below regulatory limits. Lead, Cd, Cu, Cr, Ni, and Hg concentrations in groundwater were similar for the biosolids-amended and fertilizer-treated sites across all sampling intervals. Zinc concentration was increased by biosolids application only for samples collected before the 1993 promulgation of the USEPA 40 CFR Part 503 rule. Iron and Mn were the only metals that were consistently increased after biosolids application; however, Mn concentrations did not exceed the 10 mg L regulatory limits. Zinc, Cu, Cd, Pb, Fe, Al, and Mn concentrations in groundwater decreased with time, coupled with the change from pre-part 503 to post-Part 503 biosolids. The concentrations of other metals, including Ni, Cr, and Hg, did not increase in groundwater with the prolonged biosolids application. The study suggests that the long-term application of biosolids at high loading rates does not result in trace metal pollution of groundwater.

Soil‐Test Methods for Florida Sands Treated with an Aluminum–Water Treatment Residual and Various Phosphorus Sources

Use of aluminum (Al)–rich water treatment residuals (Al‐WTR) has been suggested as a practice to immobilize excessive phosphorus (P) in Florida soils that could represent an environmental hazard. Fertilizer P requirements can differ in WTR‐amended and unamended soil, so careful selection of soil‐testing methodology is necessary. Acidic extractants can dissolve WTR sorbed P and overestimate plant‐available P. We evaluated the suitability of the Mehlich 1 P (M‐1P) and other agronomic soil‐test procedures in an Al‐WTR‐treated Florida soil. Bahiagrass (paspalum notatum Fluggae), ryegrass (Lolium perenne L.), and a second bahiagrass crop were grown in succession in a Florida topsoil amended with four sources of P at 44 kg P ha−1 (P‐based rates) and 179 kg PAN ha−1 [nitrogen (N)–based rates] and three WTR rates (0, 10, and 25 g kg−1 oven‐dry basis). Both water‐extractable P (WEP) and iron (Fe) strip P (ISP), but not M‐1P, values of soil sampled at planting of each grass were greater in the absence than in the presence of WTR. Total plant P uptake correlated with WEP (r2 = 0.82***) and ISP (r2 = 0.75***), but not M‐1P (r2 = 0.34***). Correlations of the dry‐matter yield, P concentration, and P uptake of the first bahiagrass were also better with WEP and ISP than with M‐1P values. However, regression of plant responses with M‐1P improved after the first crop of bahiagrass. Both WEP and ISP values were better predictors of available soil P than M‐1P in a field study with same four P sources surface applied to established bahiagrass at the same two P rates, with and without WTR. Both WEP and ISP are recommended as predictors of P adequacy in soils treated with WTR, especially for soils recently (< 5 months) treated with Al‐WTR.