J. Thomas Sims

Advances in the Characterization of Phosphorus in Organic Wastes: Environmental and Agronomic Applications

There is international interest today in the fate and transformation of phosphorus (P) applied to soils due to historical overapplication of P from organic wastes. This overapplication has increased soil solution P concentrations and enriched the erodible fraction of soil with P. This is of major concern as significant water quality deterioration can occur if P applied to soils in organic wastes reaches water bodies. Just as the bioavailability of P compounds depends upon their chemical form, it is becoming increasingly apparent that information about different forms of P is needed for holistic management of organic wastes. A number of chemical and biological methods have been employed to partition total P into more specific chemical forms in organic wastes. However, there has been no previous effort to review and synthesize the literature and to critically analyze the various techniques with promise for chemical speciation of P in organic wastes. In this chapter, we review various types of organic wastes and factors affecting P composition in organic wastes, from production to land disposal. Then, we discuss the various methods that have been used to characterize P forms, including water extractable P (WEP) physicochemical fractionation, sequential chemical fractionation, enzymatic hydrolysis, nuclear magnetic resonance (NMR), and x‐ray absorption near edge structure (XANES) spectroscopy. To summarize the conclusions, WEP is quick chemical test that should be employed to determine the readily dissolved P in organic wastes and to assess the potential risk of wastes on water quality. The potential bioavailability of P forms in the liquid wastes can be similarly assessed by a rapid and low cost physicochemical fractionation method. Enzymatic hydrolysis and solution state NMR can be of great benefit to characterize organic P species in wastes, whereas solid‐state NMR and XANES spectroscopy are better suited to study the inorganic P minerals in the wastes. NMR and XANES methods are both quantitative and can be used to study the influence of management practices on P speciation. Solid‐state NMR and XANES methods are capable of performing analysis of heterogeneous material and provides complementary information about P compounds in organic wastes. The combined use of sequential chemical fractionation and spectroscopic methods (NMR, XANES) allows for accurate identification of P compounds in the sequential extracts. Case studies are included throughout the chapter to discuss wider applicability of a particular method. We conclude this chapter by suggesting that more than one method may be necessary for complete determination of P species in organic wastes.

Phosphorus soil testing: Innovations for water quality protection

Abstract Modern agricultural management practices for phosphorus (P), including soil testing, can no longer focus exclusively on soil fertility and agricultural productivity but must also address the role of agricultural P in nonpoint source pollution of surface waters. The eutrophication of streams, rivers, lakes, and bays as a result of P loss from soil to water points to the need for advances in soil testing that can contribute to water quality protection. A concerted research effort to modify, refine, and advance soil testing for P to achieve environmental as well as agronomic objectives has been underway for the past decade; unfortunately, little of this research has been adopted by soil testing programs in the United States. The intent of this paper is two‐fold. First, to briefly review some of this research, illustrating its potential value in soil P management programs that, by necessity, must today have both agronomic and environmental components. And second, to provide recommendations as to how ...

Evidence for struvite in poultry litter: effect of storage and drying.

The use of spectroscopic techniques (especially phosphorus-31 nuclear magnetic resonance [(31)P-NMR] and X-ray absorption near edge structure spectroscopy) has recently advanced the analysis of the speciation of P in poultry litter (PL) and greatly enhanced our understanding of changes in P pools in PL that receive alum (aluminum sulfate) to reduce water-soluble P and control ammonia emissions from poultry houses. Questions remain concerning changes of P species during long-term storage, drying, or after application of PL to cropland or for other uses, such as turfgrass. In this study, we investigated a set of six PL samples (of which three were alum-amended and three were unamended) that had been characterized previously. The P speciation was analyzed using solid-state (31)P-NMR spectroscopy, and the mineralogy was analyzed by powder X-ray diffraction (XRD) after storing the samples moist and dried for up to 5 yr under controlled conditions. The magnesium ammonium phosphate mineral struvite was identified in all but one PL samples. Struvite concentrations were generally lower in dried samples (< or = 14%) than in samples stored moist (23 and 26%). The moist samples also had higher concentrations of phosphate bound to aluminum hydroxides. Solid-state NMR spectroscopy was in general more sensitive than XRD in detecting and quantifying P species. Although phosphate associated with calcium and aluminum made up a large proportion of P species, they were not detected by XRD.

Assessment of phosphorus leaching losses from a free draining grassland soil

Intact soil monoliths (70 cm deep, 50 cm diameter), collected from a free draining Lismore silt loam soil (Udic Haplustept) under grassland, were used to evaluate phosphorus (P) leaching for two years. The objective of the study was to investigate the effect of the application of mineral P fertiliser (at 45 or 90 kg P ha–1 y–1) and/or farm dairy effluent (FDE) (30 to 60 kg P ha–1 y–1) on P losses by leaching. Annual mean total P (TP) concentrations and losses were higher from the treatments that received both FDE and P fertiliser (203–429 μg L–1; 1.4–2.5 kg ha–1) compared with P fertiliser alone (77–151 μg L–1; 0.6–1.3 kg ha–1). The form of applied P influenced the pattern of P forms leached. For example, significantly higher P losses in different P forms were observed for the combined mineral P fertiliser and FDE treatment (P45/FDE200) than fertiliser alone (P90/N200/U). This is due to the inclusion of liquid FDE in the former treatment although the total P inputs were similar for both treatments. This illustrates the potential of these soils to adsorb soluble inorganic P applied from mineral P fertiliser, while FDE contained unreactive P forms that were mobile in the soil profile. There was a distinct pattern of P forms leached in the following order: particulate unreactive P (PUP: 40–70%)>dissolved unreactive P (DUP: 14–53%)>particulate reactive P (PRP: 5–12%)>dissolved reactive P (DRP: 1–11%). Results also suggest that changing the irrigation method from flood to spray may be the most effective means to reduce P loss in these stony, free-draining soils.

A comparison of Mehlich I and Mehlich III extractants as predictors of manganese, copper and zinc availability in four Delaware soils

Abstract The relative effectiveness of Mehlich I (.025N H2SO4 + .05N HCl) and Mehlich III (0.2N CH3COOH + 0.25N NH4NO3 +.015N NH4F + .013N HNO3 + .001M EDTA) extractants as predictors of Mn, Cu and Zn uptake was assessed in a greenhouse experiment with four Delaware soils. The soils were adjusted to eight pH levels by addition of Ca(OH)2 or elemental S, and received comparable amounts of Mn, Cu and Zn as either (1) MnSO4 + CuSO4 + ZnSO4 or (2) Poultry Manure. Mehlich 1 and III extractable Mn and Zn, but not Cu, were well correlated in most instances. Excellent correlations were obtained between Mn uptake and Mehlich I and Mehlich III extractable Mn, for all soils and sources. In general, however, neither Zn nor Cu was found to correlate well with plant uptake. Based on this study, conversion to Mehlich III, as a routine soil test extractant for micronutrients, would not result in a significant improvement over the currently used Mehlich I extractant.

Sorption of atrazine and dicamba in Delaware coastal plain soils: a comparison of soil thin layer and batch equilibrium results

The mobility and retention of atrazine and dicamba in six Atlantic Coastal Plain soils were estimated by soil thin-layer chromatography (soil-TLC). The soils studied were representative of the major agricultural regions in Delaware and were sampled, by horizon, to the water table. Four horizons from each profile were leached simultaneously with distilled water on one soil-TLC plate. Two values were obtained from each plate: the ratio of the distance traveled by the herbicide center of mass over that traveled by the solvent front (Rm), and a sorption distribution coefficient (Kd). The Rm values ranged from 0·06 to 0·94 for atrazine and from 0·80 to 0·94 for dicamba. Herbicide mobility was found to be greatest in coarse-textured soil horizons that contained low levels of organic matter, clay, and Fe and Al oxides. Correlation analysis indicated that effective cation exchange capacity, exchangeable acidity, exchangeable aluminum, and clay were useful predictive variables or both atrazine mobility and sorption. Organic matter was not useful for predicting soil-TLC derived sorption estimates; however, it was correlated to Kd-batch estimates. Distribution coefficients calculated from soil-TLC data were found to be in general agreement with Kd values obtained for the same soils by batch equilibrium techniques. The average Kd-soil-TLC values for atrazine and dicamba were 2·09(±2·24) and 0·03(±0·02), respectively. The ratio of the batch Kd to the soil-TLC Kd ranged from 0·1 to 19 (x=1·6, SD=3·8) for atrazine and from 2·9 to 38 (x=12·6, SD=8·7) for dicamba. Thus, although for some horizons agreement between the two methods was good, for other horizons significant discrepancies existed. It is suggested that the soil-TLC gives results under non-equilibrium conditions, whereas the batch procedure is, by definition, at quasi-equilibrium. These fundamental differences may account for the observed differences between the two methods. It is also suggested that, due to this difference, the soil-TLC procedure can provide additional information relevant to herbicide partitioning in the field environment that is not provided by traditional batch equilibrium techniques.

Assessing potential impacts of a wastewater rapid infiltration basin system on groundwater quality: a delaware case study.

Rapid infiltration basin systems (RIBS) are receiving increased interest for domestic wastewater disposal in rural areas. They rely on natural treatment processes to filter pollutants and use extremely high effluent loading rates, much greater than natural precipitation, applied to a small geographic area instead of disposal to surface water. Concerns exist today that adopting RIBS in areas with shallow groundwater and sandy soils may increase ground and surface water pollution. We conducted a field study of RIBS effects on N and P concentrations in soils and groundwater at Cape Henlopen State Park, Delaware, where a RIBS designed and operated following USEPA guidance has been used for >25 yr. Site and wastewater characteristics (water table of 8 m, Fe- and Al-oxide coatings on soils, organic-rich effluent) were favorable for denitrification and P sorption; however, we found high P saturation, reduced soil P sorption capacity, and significant total P accumulation at depths >1.5 m, factors that could lead to dissolved P leaching. Very low soil inorganic N levels suggest that wastewater N was converted rapidly to NO-N and leached from the RIBS. Extensive groundwater monitoring supported these concerns and showed rapid offsite transport of N and P at concentrations similar to the effluent. Results suggest that high hydraulic loads and preferential flow led to flow velocities that were too large, and contact times between effluent and soils that were too short, for effective N and P attenuation processes. These findings indicate the need for better site characterization and facility designs to reduce and monitor contaminant loss from RIBS in similar settings.

Impact of farm‐dairy effluent application on the amounts and forms of phosphorus loss by leaching from irrigated grassland

Abstract Sufficient evidence exists to support the hypothesis that the eutrophication of surface waters is accelerated by increased transfer of nutrients (e.g., phosphorus, P) from landscape to water. The objective of this paper is to combine the results of a lysimeter experiment that used intact soil monolith lysimeters (50 cm diameter, 70 cm deep) and a field experiment that used field plots (10 × 2 m2) of a Lismore stony silt loam soil (Udic Ustochrept). The soils received mineral P fertiliser alone at 45 kg P ha−1 yr−1 or in combination with farm‐dairy effluent (FDE) at 200 or 400 kg N ha−1 yr−1. Annual mean total P concentrations and losses were two‐ to threefold higher from the soil amended with both FDE and P fertiliser than P fertiliser alone. The higher losses as particulate unreactive P during irrigation seasons are attributed to the regular inputs of high intensity flood irrigation, which increased the transfer of soil particles from the soil profile. Greater than 60% of P loss occurred immediately following FDE application over a 2‐year period, highlighting the importance of preferential flow in this soil. Phosphorus‐31 nuclear magnetic resonance analysis showed that FDE was rich in inorganic orthophosphate (86%) while leachate contained only 12% of inorganic orthophosphate. This indicated that inorganic P applied in FDE was sorbed because of the high P fixation capacity of Lismore subsoil, which is due to higher amounts of Fe and Al. On the other hand, orthophosphate monoesters and diesters were only 13% of P in FDE, compared with 88% in leachate suggesting that organic P forms are mobile in the soil profile, and are selectively transported through soil. The Olsen P and isotopic exchange parameters (concentration of inorganic P in the soil solution (CP) and the quantity of P that is immediately available to plants (E1min)) of Lismore soil increased with increase in P application from mineral P fertiliser and FDE. This suggests that P fixation sites in soil may be getting saturated with applied P inputs.

Changes in soil test phosphorus from broiler litter additions

Abstract Nutrient surpluses on the Delmarva Peninsula have led to a continual accumulation of soil test phosphorus (STP), a potential source for transport of phosphorus (P) to surface waters. This article examines the effects of initial soil test P concentrations and broiler litter additions on STP accumulation. Broiler litter (BL) was applied at rates of 0, 2.5, 5, 7.5, and 10 g kg−1 (dry weight) to three soils: an Evesboro sandy loam (Mesic, coated Typic Quartzipsamments), a Pocomoke sandy loam (coarse‐loamy, siliceous, thermic typic Umbraquults), and a Matapeake silt loam (fine‐silty, mixed, semiactive, mesic Typic Hapludults). Soils and BL were incubated for 16 weeks with subsamples analyzed after 4 and 16 weeks. There was a linear increase in STP (Mehlich‐3), water‐soluble P (WS‐P), iron‐oxide strip‐extractable P (FeO‐P), and Mehlich‐3 phosphorus saturation ratio (M3‐PSR) with broiler litter additions. Regression analysis indicated few significant differences in STP response to added BL between soils within the same soil group having different initial STP levels. Correlation analysis and stepwise regression indicated that increases in WS‐P and FeO‐P from added BL were more closely related to the degree of P saturation of the soil rather than traditional STP measurements. Therefore, decisions regarding manure placement within a watershed should be based on the potential P sorption capacity of the soil as well as potential P transport pathways when the goal is the reduction of P transfer to waterbodies.

Phosphorus Leaching in Soils Amended with Animal Manures Generated from Modified Diets.

New dietary modifications for dairy (reducing P content in feed) and poultry (addition of feed additives such as phytase) aim to reduce P excretion in manures. Our objective was to investigate if dietary changes were effective at reducing P leaching loss on land application of manures. We used 54 undisturbed lysimeters (30 cm diameter, 50 cm deep) collected from three typical mid-Atlantic soils. Lysimeters received 85 kg total P ha from fertilizer (superphosphate), dairy manures generated from low- or high-P diets, or broiler litters generated from normal diet or reduced P- and phytase-amended diets. Lysimeters were irrigated with 50 mm of water each week for 9 wk. The major forms of P in the leachate were dissolved (dissolved unreactive > dissolved reactive P [DRP]) rather than particulate (total particulate P). The higher P solubility (100%) in superphosphate resulted in greater leaching of DRP, whereas the lower P solubility (<30%) in dairy manures or broiler litters resulted in lower DRP leaching from soils. Preferential flow in two soils caused greater DRP leaching; this effect was more pronounced in the superphosphate-amended than in the manure/litter-amended lysimeters. The dairy and poultry dietary modification was effective at reducing the amount of P in manures and litters. However, the application of treatments at similar P rate (85 kg ha) resulted in the addition of a higher amount of manure (54-66%) in lysimeters that received low-P dairy manure-amended and phytase-amended broiler litter, which then controlled P leaching from soils.