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Controlling dissolved phosphorus (P) losses to surface waters is challenging as most conservation practices are only effective at preventing particulate P losses. As a result, P removal structures were developed to filter dissolved P from drainage water before reaching a water body. While many P removal structures with different P sorption materials (PSMs) have been constructed over the past two decades, there remains a need to evaluate their performances and compare on a normalized basis. The purpose of this review was to compile performance data of pilot and field-scale P removal structures and present techniques for normalization and comparison. Over 40 studies were normalized by expressing cumulative P removal as a function of cumulative P loading to the contained PSM. Results were further analyzed as a function of retention time (RT), inflow P concentration, and type of PSM. Structures treating wastewater were generally more efficient than non-point drainage water due to higher RT and inflow P concentrations. For Ca-rich PSMs, including slag, increased RT allowed for greater P removal. Among structures with low RT and inflow P concentrations common to non-point drainage, Fe-based materials had an overall higher cumulative removal efficiency compared to non-slag and slag materials.

The purpose of this chapter is to present the detailed laboratory methods and methodology of PSM characterization that are necessary for designing a P removal structure and screening PSMs for safety. Through the information in this chapter, laboratory personnel can follow detailed instructions for conducting a complete PSM characterization. At the most basic level, designing a P removal structure requires knowledge of the quantitative relationship between dissolved P added to a PSM and the P removed by the PSM, expressed on a mass basis. This can only be achieved by producing a flow-through “design curve” that is specific to a given retention time and inflow P concentration for the PSM of interest. This P removal design curve can either be measured directly or predicted from a chemical characterization: detailed methods for both are provided. Physical characterization methods necessary for designing a P removal structure are also provided. Last, methods of safety characterization of PSMs are given. The characterization methods given in this chapter will provide all of the necessary PSM inputs required to design a P removal structure. Instructions on how to obtain site inputs and how to design a P removal structure is given in Chap. 6.

With the problem of excess P in surface waters established and various non-point sources identified in Chap. 1, this chapter moves deeper into the mechanisms of P transport from terrestrial sources to surface waters. Specifically, P transport is split up into two main categories of sources (incidental and legacy), and broadly described as two main forms in drainage waters: particulate P and dissolved P. The two P forms are especially critical since they behave differently with regard to aquatic bioavailability and the means in which each form is transported. These inherent differences translate to differences in the types of BMPs that can be utilized for reducing transport of each of the P forms, potency of each P form for causing eutrophication, and the temporal aspect of P losses. This chapter focuses more on legacy P sources rather than incidental P losses because of the greater difficulty in controlling the latter. Phosphorus management in the context of legacy P sources is presented as a system in three main categories: (1) prevention of legacy P formation, (2) containment of legacy P, and (3) remediation of legacy P. While some conventional BMPs are effective at reducing particulate P and few are effective at partially containing dissolved transport from legacy P sources, none will remediate dissolved P losses from legacy P sources in the short-term. Because of the unique temporal aspect of legacy P and dissolved P transport, there is a need to utilize both long-term and short-term remediation for reducing dissolved P transport. The long-term remediation of legacy P sources is achieved through soil P drawdown with plants, and the dissolved P losses that occur in the short-term during that slow process can be remediated with P removal structures.

This chapter begins with a detailed presentation of the basic design methodology by estimating the mass of a specific PSM required for a specific site. This “design curve” will be thoroughly explained with several examples, as this is the heart of a proper design. Next, the reader is walked through the steps of a site assessment, with examples, that are necessary for obtaining all of the proper inputs for designing a PSM-specific and site-specific P removal structure. This includes how to estimate peak flow rates, average annual flow volume, typical dissolved P concentrations in runoff or subsurface drainage, and hydraulic head. Other inputs necessary for a proper design include the maximum area, or for ditch filters, the maximum length, the diameter of the drainage pipe to be used in the structure, the target retention time, maximum flow rate, and P removal and lifetime goals. Using all of the inputs, we present the general procedure for designing a site-specific P removal structure that meets the user constraints. This chapter also includes a detailed discussion on designing structures that flow from the top-downward vs. the bottom-upward, achieving proper drainage in a structure, and the challenges of balancing retention time with peak flow rate requirements. Although not necessary for design, we include instructions on how to predict the amount of particulate P that a P removal structure will remove. All necessary equations for obtaining necessary site inputs and conducting a design are given in this chapter.

This chapter is dedicated to the most important component of the P removal structure: PSMs, which are the component that actually removes the dissolved P. Phosphorus sorption materials are presented in great detail and explained. Many of these materials are by-products from various industries such as drinking water treatment, steel production, acid mine reclamation, energy generation, metal casting, wall board production, and bauxite mining. Other PSMs are manufactured for the sole purpose of removing dissolved P. The chemical and physical properties relevant to P removal structures are discussed in the context of choosing a suitable PSM for the situation, with a general characterization of several PSMs presented. This will include a discussion of the main mechanisms of P removal by PSMs and the implications of those mechanisms on design. Specifically, the influence of retention time and inflow P concentration on P removal by different types of PSMs are discussed in detail. The reader will clearly understand how the retention time and the inflow P concentration can have a dramatic impact on the design of a site-specific P removal structure. The common “paradox of PSMs” is presented: usually PSMs with the greatest ability to adsorb P tend to conduct water poorly (i.e. low hydraulic conductivity), and vice versa. While there are some exceptions to this, the implications of this issue are explained with several solutions provided. In addition to a general guide in choosing a suitable PSM, the chapter concludes with a discussion on safety considerations of PSMs that originate as by-products, and the need to screen some materials for safety. Recommendations and thresholds for PSM safety screening are provided.

This chapter discusses the disposal options for the spent PSMs after they have achieved their useful lifetime in a P removal structure. This includes (1) use of the spent PSMs as a soil P fertilizer, (2) use as a plant growth media, (3) assessing P availability in the spent PSMs, (4) potential P stripping from the PSMs and recharge, (5) land application of spent PSMs for purposes other than P fertility, (6) non-plant use of spent PSMs, and (6) safety considerations in beneficial re-use of spent PSMs. The majority of this discussion is on the land application of PSMs to soils, and any potential benefit that that the PSMs may have on soil quality and plant growth. The potential beneficial re-use of spent PSMs strongly depends on how stable the PSM-bound P is, and forms of P contained on it. A discussion on the economics of P-stripping and PSM regeneration is also included. Several tables consisting of safety characterization data from various by-product PSMs are shown.

With the establishment of how to design a PSM- and site-specific P removal structure, this chapter is intended for those readers who have the Phrog (Phosphorus Removal Online Guidance) software, or would like to learn about the software. The Phrog software allows the user to quickly design and examine many different options for a structure design at a specific site and PSM to be utilized. The user simply inputs the required PSM information, site assessment information, and the targets: retention time, desired peak flow rate, lifetime, and P removal. The resulting output consists of the required mass and orientation of the PSM, the required number of drainage pipes, and a table that lists the annual P removal until the PSM is no longer effective at removing P. In addition, the ability of the software to predict the performance, i.e. lifetime and P removal, for an already existing structure will also be explained and illustrated. The use of the software for achieving these purposes in a variety of different situations and types of P removal structures will be illustrated with software screenshots of both inputs and outputs. Examples will include design of a confined bed runoff filter, ditch filter, subsurface tile drain filter, bio-retention cell, surface inlet, and waste-water treatment plant.

The general theory of P removal structures for treating dissolved P is presented and explained along with the four necessary components for any P removal structure. While P removal structures can take many different forms, these four components must be present for a P removal structure to be effective. These four components are (1) an effective PSM in a sufficient quantity, (2) containment of the PSM, (3) the ability to replace the PSM when necessary, and (4) passive drainage via gravity at sufficient flow rates suitable for the site. The general site requirements for location of a P removal structure are also presented along with a discussion of the many different applications of this technology. A demonstration is given on how to choose the most efficient locations for reducing dissolved P loads with a P removal structure. These concepts will be illustrated through the presentation and illustration of several different styles of P removal structures. For example, ditch filters, surface confined beds for runoff interception, subsurface tile drain filters, surface and blind inlets, “bio-retention cells”, etc. Last, we provide examples of how the P removal structure can be utilized for point sources such as municipal and domestic wastewater.

Phosphorus is introduced at its most basic level: an element on the periodic table and the various forms and abundance in which it exists, as well as its necessity for all biological function, including agricultural production. This chapter serves to lay the foundation and justification for efforts to reduce P loading to surface waters. It describes eutrophication, the major problem caused by excess P in surface waters and describes the resulting negative impact that it has on recreation, drinking water treatment, and ecosystem diversity. The major sources of P to surface waters is discussed, as separated into point and non-point sources, focusing dominantly on non-point sources and describing how such non-point sources came to exist. Examples of non-point urban and agricultural scenarios are given, with some data presented. Within non-point sources, the focus is mostly on “legacy” P in soils since this P source can sustain P transport for several decades.

Made available in DSpace on 2018-12-11T16:46:12Z (GMT). No. of bitstreams: 0 Previous issue date: 2017-04-01 Improving soil organic matter (SOM) quality in tropical acid soils is important for increasing the sustainability of agricultural ecosystems. This research evaluated the effect of the surface application of lime and phosphogypsum on the quality and amount of SOM in a long-term crop rotation under no-till conditions. The research was performed in a kaolinitic, thermic Typic Haplorthox for 12 years with annual crops under no-till. The treatments included no soil amendments, and amendment with phosphogypsum, lime, and lime + phosphogypsum. After three applications of soil amendments (2002, 2004, and 2010), surface liming increased the SOM input through addition of aboveground and root biomass, varying amount according to crop species, growing season, and soil depth. Although phosphogypsum had no effect on plant biomass production, the application of phosphogypsum with lime increased nitrogen (N) by up to 50% in the uppermost soil depths. The application of lime alone significantly increased the total organic carbon (TOC) at all depths, although the greatest effects were observed at 0.10–0.20 and 0.20–0.40 m, with an increase of 44% and 41%, respectively. Moreover, lime + phosphogypsum also exhibited the highest potential for C mineralization, which was attributed to an increased proportion of TOC as particulate organic carbon (POC). The proportion of TOC as humin and fulvic acid increased with the application of lime + phosphogypsum at 0–0.05 m, with an increase from 55% to 92% and from 1.4% to 1.6%, respectively. Overall, the combination of lime and phosphogypsum increased both the labile and stable C pools. São Paulo State University (UNESP) College of Agricultural Sciences Department of Crop Science, P. O. Box 237 National Soil Erosion Research United States Department of Agriculture São Paulo State University (UNESP) College of Agricultural Sciences Department of Crop Science, P. O. Box 237

Pairing denitrifying woodchip bioreactors and phosphorus-sorbing filters provides a unique, engineered approach for dual nutrient removal from waters impaired with both nitrogen (N) and phosphorus (P). This column study aimed to test placement of two P-filter media (acid mine drainage treatment residuals and steel slag) relative to a denitrifying system to maximize N and P removal and minimize pollution swapping under varying flow conditions (i.e., woodchip column hydraulic retention times (HRTs) of 7.2, 18, and 51 h; P-filter HRTs of 7.6-59 min). Woodchip denitrification columns were placed either upstream or downstream of P-filters filled with either medium. The configuration with woodchip denitrifying systems placed upstream of the P-filters generally provided optimized dissolved P removal efficiencies and removal rates. The P-filters placed upstream of the woodchip columns exhibited better P removal than downstream-placed P-filters only under overly long (i.e., N-limited) retention times when highly reduced effluent exited the woodchip bioreactors. The paired configurations using mine drainage residuals provided significantly greater P removal than the steel slag P-filters (e.g., 25-133 versus 8.8-48 g P removed m-3 filter media d-1, respectively), but there were no significant differences in N removal between treatments (removal rates: 8.0-18 g N removed m-3 woodchips d-1; N removal efficiencies: 18-95% across all HRTs). The range of HRTs tested here resulted in various undesirable pollution swapping by-products from the denitrifying bioreactors: nitrite production when nitrate removal was not complete and sulfate reduction, chemical oxygen demand production and decreased pH during overly long retention times. The downstream P-filter placement provided a polishing step for removal of chemical oxygen demand and nitrite.

Land application of gypsum has been studied and utilized in agriculture and environmental remediation for many years. Most of the published literature has focused on gypsum application impacts on soil properties rather than crop yields. This literature review was conducted to (i) gather results from gypsum application studies relevant to crop grain yield, soil physical–chemical properties, and environmental impact; (ii) report different methods for determining gypsum application rates; (iii) suggest recommendations for future studies on land application of gypsum. Improvement in plant nitrogen use efficiency was rarely discussed as a potential mechanism for improving yield. Free Al activity has been demonstrated to be more correlated with plant yield responses to gypsum application than exchangeable Al or Al saturation. However, few authors reported Al speciation and Al activity. While gypsum is reported to improve soil chemical properties in most cases, these changes do not necessarily translate to increases in yield. Improvements in physical properties for nonsodic soils are not consistent. It is difficult to exactly determine the positive effects from gypsum application that are responsible for yield increases, since there are often many simultaneous physical and chemical changes occurring in the soil. Improvement in crop yield may be a result of an additive or synergistic effect of each of these potential changes. In addition, these potential changes, as varied as they are, appear to also vary with crop, soil type, and rainfall regime. Therefore, meta-analysis of gypsum experiments is highly recommended in order to improve gypsum recommendations across diverse environments.

Introduction Total coffee production in the world in 2013 was 8.7 million Mg of coffee beans. Coffee must be processed after harvest to separate beans from the husk, and the post-harvest process can generate different types of residues. Knowing that 50 % of the harvested coffee is husk, it is important to consider that these by-products can contribute to environmental problems if not disposed of properly. There is a need to find alternatives to the piling of coffee husk as a means of disposal at coffee farms. The objectives in this experiment were to characterize five types of coffee processing residues and assess their value as potassium (K) fertilizer by examining K release. Results Chemical characteristics of coffee residues varied with processing method, such as wet and dry processes. Application of residues to soil columns followed by 40 weeks of simulated leaching increased total K content in the soil for all treatments based on application rate, except for enriched and three-year composted coffee husk (3ycomp). Coffee processing residues had higher concentrations of K leached compared with the control with no K application, but only 3ycomp was higher than other coffee processing residues. Total K released from coffee residues increased linearly with application rate, but the decomposition of the coffee residues was low, which suggest that K release from coffee processing residues is not related to decomposition. Conclusion Post-harvest coffee processes impacted concentrations of K, nitrogen, carbon, cellulose, hemicellulose, lignin, phenol, pH, and electrical conductivity among the coffee processing residues. The K release was high (over 90 %), but it did not depend on the type of coffee processing residue, and thus, the residues can be a substitute for a mineral source of K applied to soils. The use of coffee processing residues as source of K did not prevent K losses by leaching. Some coffee residues resulted in greater K leaching than mineral KCl applied at the same rate.

Decommissioned animal waste lagoons contain large quantities of nutrients including nitrogen (N) and phosphorus (P) and can cause pollution of nearby water resources. Using short-rotation woody crops (SRWCs) for nutrient uptake and biomass production might be an inexpensive and eco-friendly method for the stabilization of decommissioned lagoons. We evaluated the annual growth performance and nutrient uptake by sycamore (Platanus occidentalis) for five growing seasons and 25 different clones of eastern cottonwood (Populus deltoides) for four growing seasons in a soil backfilled, de-watered swine lagoon in north-central Oklahoma. Growth performance and nutrient uptake of cottonwood was higher than the sycamore in our study. At the end of the study, 5-year old sycamore reached an average height of 5.84 m [standard error (SE) = 0.39] and had an average diameter at breast height (dbh) of 5.91 cm (SE = 0.20), compared to 4-year old cottonwood height of 7.58 m (SE = 0.15) and dbh of 8.22 cm (SE = 0.34), respectively. Sycamore produced almost 30 Mg ha−1of total biomass, whereas cottonwood produced 53 Mg ha−1 by the end of the study. Total N and P uptake by sycamore was 327 (SE = 24) and 51 (SE = 4) kg ha−1 respectively, whereas cottonwood N and P uptake was 699 (SE = 41) and 99 (SE = 6) kg ha−1, respectively, by the end of the study. We conclude that SRWCs can use substantial amounts of nutrients from the decommissioned lagoons while producing wood and fiber products.

Phosphorus eutrophication of lakes and streams, coming from drained farmlands, is a serious problem in areas with intensive agriculture. Installation of phosphate (P) sorbing filters at drain outlets may be a solution. The aim of this study was to improve the understanding of reactions involved in P sorption by three commercial P sorbing materials, i.e. Ca/Mg oxide-based Filtralite-P, Fe oxide-based CFH-12 and Limestone in two particle sizes (2–1 mm and 1–0.5 mm), by means of isothermal titration calorimetry (ITC), sorption isotherms, sequential extractions and SEM-EDS. The results indicate that P retention by CFH is due to surface complexation by rapid formation of strong Fe–P bonds. In contrast, retention of P by Filtralite-P and Limestone strongly depends on pH and time and is interpreted due to formation of calcium phosphate precipitate(s). Consequently, CFH can unambiguously be recommended as P retention filter material in drain outlets, whereas the use of Filtralite-P and Limestone has certain (serious) limitations. Thus, Filtralite-P has high capacity to retain P but only at alkaline pH (pH ≥ 10) and P retention by Limestone requires long-time contact and a high ratio between sorbent and sorbate.

The current increase in oil and gas drilling activity has resulted in increased production of oil-base “mud” (OBM) in need of disposal. Land application of OBM to agricultural land is a common disposal technique that presents agronomic and environmental challenges since the material is rich in petroleum hydrocarbons. The objective of this study was to determine the effect of mixing OBM with bulking materials on hydrocarbon degradation and forage production after land application of the mixtures. An OBM was collected from Oklahoma and characterized for environmentally relevant properties such as total petroleum hydrocarbons (TPH) and trace metals. The OBM was bulked with either limestone, gypsum, or caliche, at a ratio of 3:1 or 1.5:1 bulking material/OBM. All mixtures were surface applied at equal TPH loading rates (8625 kg ha–¹) and soil samples taken at 7, 45, 60, and 170 d after application for evaluation of TPH, electrical conductivity (EC), pH, and sodium absorption ratio (SAR). After 7 d >50% of applied TPH degraded, which resulted in soil concentrations less than thresholds recommended for residential neighborhoods. By Day 170, 99% of applied TPH degraded. There was mostly no difference in TPH degradation as a function of type and amount of bulking agents used with OBM. Application of OBM did not significantly decrease forage yield compared to unamended control. Therefore, use of caliche, limestone, or gypsum bulked with OBM at a 1.5:1 ratio (bulking agent/OBM) would suffice for achieving acceptable TPH degradation when mixtures are surface applied and non-incorporated.

Published in Agron. J. 106:1722–1734 (2014) doi:10.2134/agronj13.0530 Copyright © 2014 by the American Society of Agronomy, 5585 Guilford Road, Madison, WI 53711. All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. ABSTRACT

In some watersheds, the majority of the total sediment load to streams and rivers is from streambanks, but insufficient data exist on actual loading from this source and the potential protective effect of riparian protection in many watersheds. Using aerial imagery, video reconnaissance for unstable banks, and streambank phosphorus (P) sampling, this research studied streambanks throughout the Barren Fork Creek (BFC) watershed within Oklahoma to address four major objectives: (i) quantify the amount of streambank erosion and failure throughout the watershed, (ii) quantify the magnitude and the intra-site and inter-site spatial variability in streambank soil chemistry, water soluble phosphorus (WSP), and total phosphorus (TP), (iii) quantify the load of WSP and TP from streambanks in the watershed, and (iv) estimate the benefit of riparian management practices. Ten streambank study sites were selected on BFC, including seven sites with existing or historic riparian forest (historically protected, HP), and three with no riparian forest (historically unprotected, HUP). Median and mean streambank migration rates were 9.5 and 17.5 m for the HP sites compared to 37.6 and 49.2 m for the three HUP sites over the seven year period. Total WSP from streambanks on BFC from unprotected and failing banks was approximately 1.2 × 10 3 kg yr −1 , which represented approximately 10% of the dissolved P load estimated from USGS gauges on BFC. The estimated TP load was approximately 9.0 × 10 4 kg TP yr −1 , which exceeded the TP load estimated from gauge data, although TP is largely sediment-bound and thus subject to sediment transport dynamics such as floodplain deposition. Streambanks represented a considerable source of P, and riparian forest sites showed significantly lower rates of retreat. The methodology of using detailed P characterization, lateral retreat rates from aerial photography, and video reconnaissance to characterize bank stability was an effective approach for assessing the WSP and TP load contribution from streambanks.

Soil Sci. Soc. Am. J. 78:147–156 doi:10.2136/sssaj2013.06.0239 Received 21 June 2013 *Corresponding author: (Chad.penn@okstate.edu). © Soil Science Society of America, 5585 Guilford Rd., Madison WI 53711 USA All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Permission for printing and for reprinting the material contained herein has been obtained by the publisher. Application of Isothermal Calorimetry to Phosphorus Sorption onto Soils in a Flow-Through System Soil Chemistry

The closure of swine farms requires decommissioning of lagoons that contain large amounts of swine solids (sludge). Sludge is typically transported and land applied to soils. However, in some cases this process could be economically prohibitive and/or unpractical. An alternative idea is to encase sludge with lagoon soil berms after removing overlying effluent, followed by establishment of forages or short-rotation woody crops on the encased sludge. The objective of this study was to investigate growth potential for several forages and tree species into a pure layer of swine sludge. Alfalfa (Meticago sativa), bermudagrass (Cynodon dactylon), switchgrass (Panicum virgatum), green ash (Fraxinus pennsylvanica), black locust (Robinia pseudoacacia), and sycamore (Platanus occidentalis) were established in 40 cm deep pots consisting of a lagoon berm soil overlaying a sludge layer for 12 w followed by analysis of aboveground and belowground biomass production. "New" and "old" sludge was collected from an active 10 year old lagoon and decommissioned 50 year old lagoon, respectively. A control (soil only) was used. Encased sludge treatments increased forage biomass production. Sycamore and green ash were sensitive to new sludge but not old sludge as these species had less biomass production in new sludge than control and showed tissue trace nutrient deficiencies. While both sludge materials contained adequate nutrients, the new sludge had a salt concentration 1.8 times higher than old sludge as indicated by electrical conductivity (12.4 mS). Thus, the forage crops and black locust were able to thrive in new sludge due to their salt tolerance.

Vegetative filter strips (VFS) are commonly used conservation measures to protect nearby receiving streams and water bodies from sediment, nutrients, pesticides, and other contaminants applied in upslope contributing areas. Their efficiency for trapping phosphorus (P) has been examined in numerous field studies, but limited research has been performed on developing predictive equations for use in their design and assessment of water quality benefits. Existing predictive equations for P trapping efficiency are based on physical characteristics of the filter or linear regressions with only sediment reduction by the filter. The objective of this research was to develop a simple empirical regression model to quantify total P trapping efficiency by a vegetative filter strip based on the hydrologic (infiltration) and sedimentological response of the filter from ten previous studies reported in the literature. A wide range of trapping efficiencies for total P was reported, with only a few observations of 100% trapping efficiency. Using a traditional multiple linear regression approach, a regression model was derived based on runoff reduction (infiltration) and sediment reduction with a coefficient of determination (R 2 ) of 0.68 and a standard error of 14.2. A linear regression between observed and predicted total P percent reduction resulted in a slope of 0.68 and intercept of 23.5%. The length of the vegetative filter strip was not a statistically important factor, but the runoff reduction (infiltration) was statistically significant in predicting total P reduction. Therefore, P trapping efficiency predictions are improved if infiltration and sedimentation are considered explicitly rather than implicitly via filter strip length. The regression model was derived independent of the initial P concentration attached to the soil, resulting in the model overpredicting P reduction for cases when the observed P reduction was less than 40%. Removing VFS observations of total P reduction in studies with initially high soil P concentrations in the VFS, where sorption may be limited, resulted in a regression model with R 2 = 0.92 and a standard error of 5.1. A linear regression between observed and predicted total P percent reduction resulted in a slope of 0.92 and intercept of 6.3%. Therefore, the proposed regression model can be used in the design or evaluation of early-stage VFS where the sorption of P is not inhibited by saturation of the soil media and/or sediment and its associated P has not accumulated in the VFS. Furthermore, the regression model can be integrated into a numerical filter strip model capable of predicting infiltration and sedimentation without the need for estimates of numerous contaminant transport parameters.

Nitrogen (N) release rate from organic materials through mineralization is affected by the organic material and environmental conditions. Determining rates of mineralization for canola (Brassica rapa L.) meal and cottonseed (Gossypium hirsutum L.) meal with or without soapstock (a waste byproduct of seed oil extraction) will establish appropriate application rates for consumers. Canola meal, cottonseed meal, cottonseed meal with soapstock, or no treatment (control) was incorporated at a rate of 4.9 g·m−2 N into three loam soils. Experimental units were incubated for 0, 3, 7, 14, 30, or 60 days while maintaining moisture at 60% water-holding capacity and then analyzed for NH4-N and NO3-N, then plant available N was calculated as NH4-N+NO3-N. Ammonium increased with each seed meal amendment during the first 14 days of incubation and then decreased. Nitrate increased in seed meal treatments during the first 14 days of incubation and then continued to increase as NH4-N ions declined. Canola meal and cottonseed meal with or without soapstock increase plant-available soil N.

Soil washing with acidic chelators followed by liming is under consideration for remediating multi-metal contaminated soils. This technique was tested by pot experiments with a mixture of chelators (MC) as a washing agent. After washing and liming treatments, corn (Zea mays L.) was planted to assess bioavailability of heavy metals. A phytoextraction with Sedum alfredii was additionally performed after corn harvest to further decrease heavy metals in the soil. The results showed that the concentrations of Cd, Pb, and Zn in the corn grain with the washing treatment were still higher than the food standard limits in China, and liming the washed soil did not effectively decrease Cd and Pb concentrations in the corn grain. Liming the washed soil significantly increased heavy metals concentrations in leachate. The concentrations of Cd, Pb, Zn, and Cu in S. alfredii after washing were increased by 42.8, 51.2, 7.3, and 25.8%, respectively, compared to nonwashed soils. Phytoextraction rates of Cd and Zn by one crop of S. alfredii after soil washing were 47.8 and 9.82%, respectively, of the soil total metal. The phytoextraction of soils with S. alfredii, and also the liming treatment alone without phytoextraction or washing, were able to reduce exchangeable heavy metal concentrations in soils. This study suggests that the bioavailability of heavy metals could still be high after washing, liming the washed soil may release the adsorbed metal-chelates, and the phytoextraction by S. alfredii after soil washing is an effective approach to deplete the mobile Cd activated by soil washing.

Streambank nutrient loading rates are a growing concern within many watersheds. Only a few studies exist on streambank soil chemistry and phosphorus (P) concentrations, spatial distributions in watersheds, and P loading rates with a consideration of the potential uncertainty associated with the estimates. More so, limited studies compare streambank P loading for streams within similar watersheds and with similar land use and management. The objectives of this research included (1) quantifying the magnitude and spatial distribution of soil pH, electrical conductivity (EC), total P concentration, dissolved P concentration, and the degree of P saturation of streambanks in a watershed; (2) quantifying whether water-soluble phosphorus (WSP) and total phosphorus (TP) loads entering the stream from streambanks are significant based on a combined mass balance and uncertainty analysis approach; and (3) contrasting streambank P concentrations and loadings between two similar streams: Spavinaw Creek (SC) ver...

Reduction of phosphorus (P) inputs to surface waters may decrease eutrophication. Some researchers have proposed filtering dissolved P in runoff with P-sorptive byproducts in structures placed in hydrologically active areas with high soil P concentrations. The objectives of this study were to construct and monitor a P removal structure in a suburban watershed and test the ability of empirically developed flow-through equations to predict structure performance. Steel slag was used as the P sorption material in the P removal structure. Water samples were collected before and after the structure using automatic samples and analyzed for total dissolved P. During the first 5 mo of structure operation, 25% of all dissolved P was removed from rainfall and irrigation events. Phosphorus was removed more efficiently during low flow rate irrigation events with a high retention time than during high flow rate rainfall events with a low retention time. The six largest flow events occurred during storm flow and accounted for 75% of the P entering the structure and 54% of the P removed by the structure. Flow-through equations developed for predicting structure performance produced reasonable estimates of structure "lifetime" (16.8 mo). However, the equations overpredicted cumulative P removal. This was likely due to differences in pH, total Ca and Fe, and alkalinity between the slag used in the structure and the slag used for model development. This suggests the need for an overall model that can predict structure performance based on individual material properties.

Agricultural drainage ditches provide a direct pathway for high nutrient loads such as phosphorus (P) from fields to surface waters. Most practices designed to reduce P loading from fields focus on overland flow and sediment-bound P; however, P transport in these landscapes can be dominated by subsurface transport of dissolved P. Filters have been designed and are currently being field-tested that utilize P sorbing materials to remove P directly from flow in ditches. Models have been developed to predict P removal and the time of filter effectiveness. While filter performance along with model development and validation is examined in separate papers, there is a need to translate these models into usable tools for watershed managers who have to decide on filter design. This study provides examples of how these models can be used to design P-removal structures containing electric arc furnace slag (EAFS) or flue gas desulphurization gypsum (FGDG). Through the use of realistic parameters for retention time, inflow P concentration and material characteristics, the presented examples demonstrate that EAFS would outperform FGDG across a range of inflow P concentrations (0.5–10 mg/L) and removing 28–65% more P. With an average inflow P concentration of 1.62 mg/L (typical for ditches on the Delmarva Peninsula, United States), a 20-Mg EAFS filter would remove 42% more P than a 31-Mg FGDG filter. In addition, the EAFS filter would have a flow rate 10 times that of the FGDG filter. The predictive equations discussed in this paper can be used to determine the cost per unit of P removed of filters containing different materials.

Sorption of fecal bacteria in soils treated with swine effluents as a fertilizer involves complex mechanisms that are functions of the effluent constituents, soil colloid properties, and fecal bacteria population. Swine effluents contribute significant solutes and organic compounds during application and potentially increase the soil solution pH and ionic strength when in contact with soils. The objective of this research was to investigate sorption of fecal bacteria on soils treated with swine effluents and to derive a fecal bacteria sorption model based on soil properties. Sorption of Escherichia coli was investigated using a series of artificial and natural soils treated with swine effluent at varying dilution ratios (i.e., manure effluent concentrations). Note that this research conducted sorption tests based on multiple strains of the E. coli population in the manure effluent, as opposed to a specific E. coli strain. Fecal bacteria in swine effluents mainly consisted of attached bacteria as opposed to free cells in suspension (i.e., planktonic form). Sorption of surface-bonded E. coli appeared to be controlled by processes occurring in the substrate (i.e., surfaces to which the bacteria attached) as a function of the soil solution pH and ion exchange. For soils up to 30% clay content and 3.0% total carbon content, nonlinear equations characterized the sorption of E. coli in the artificial and natural soils. For soils with percent clay less than or equal to 11%, total carbon played a primary role in the estimated sorption of fecal bacteria. For soils with clay percentages larger than 11% and lower than 30%, sorption of fecal bacteria was directly correlated to amorphous aluminum and iron concentrations, percent clay, and total carbon. In addition, dispersion resulting from alkalinity buildup due to adding effluent to the soils in the presence of soil organic matter decreased observed sorption of E. coli in some cases, especially at higher effluent ratios. Experimental data indicated that predictions based exclusively on the percent clay content overestimated sorption of E. coli on soils treated with swine effluent in most soils. Manure effluent concentration, the presence of attached bacteria, and soil dispersion under high effluent concentrations should be considered when modeling fecal bacteria transport in soils. Future environmental research should be conducted with actual manure sources and multiple strains of an E. coli population.

Phosphorus (P) removal structures have been shown to decrease dissolved P loss from agricultural and urban areas which may reduce the threat of eutrophication. In order to design or quantify performance of these structures, the relationship between discrete and cumulative removal with cumulative P loading must be determined, either by individual flow-through experiments or model prediction. A model was previously developed for predicting P removal with P sorption materials (PSMs) under flow-through conditions, as a function of inflow P concentration, retention time (RT), and PSM characteristics. The objective of this study was to compare model results to measured P removal data from several PSM under a range of conditions (P concentrations and RT) and scales ranging from laboratory to field. Materials tested included acid mine drainage residuals (AMDRs), treated and non-treated electric arc furnace (EAF) steel slag at different size fractions, and flue gas desulfurization (FGD) gypsum. Equations for P removal curves and cumulative P removed were not significantly different between predicted and actual values for any of the 23 scenarios examined. However, the model did tend to slightly over-predict cumulative P removal for calcium-based PSMs. The ability of the model to predict P removal for various materials, RTs, and P concentrations in both controlled settings and field structures validate its use in design and quantification of these structures. This ability to predict P removal without constant monitoring is vital to widespread adoption of P removal structures, especially for meeting discharge regulations and nutrient trading programs.

Phytoextraction using hyperaccumulating plants is generally time-consuming and requires the cessation of agriculture. We coupled chelators and a co-cropping system to enhance phytoextraction rates, while allowing for agricultural production. An experiment on I m3 lysimeter beds was conducted with a co-cropping system consisting of the hyperaccumulator Sedum alfredii and low-accumulating corn (Zea Mays, cv. Huidan-4), with addition ofa mixture of chelators (MC), to assess the efficiency of chelator enhanced co-crop phytoextraction and the leaching risk caused by the chelator. The results showed that the addition of MC promoted the growth of S. alfredii in the first crop (spring-summer season) and significantly increased the metal phytoextraction. The DTPA-extractable and total metal concentrations in the topsoil were also reduced more significantly with the addition of MC compared with the control treatments. However, mono-cropped S. alfredii without MC was more suitable for maximizing S. alfredii growth and therefore phytoextraction of Zn and Cd during the autumn-winter seasons. No adverse impact to groundwater due to MC application was observed during the experiments with three crops and three MC applications. But elevated total Cd and Pb concentrations among subsoils compared to the initial subsoil concentrations were found for the co-crop + MC treatment after the third crop.

Although N fertilizers are not acidic, their inputs to soil are acid forming. As a result of the long-term use of N fertilizers, soils in the Great Plains are becoming more acidic and this acidity may become a yield-limiting factor. In 1970, long-term plots were initiated to compare sources (anhydrous NH 3 , NH 4 NO 3 , urea, and S-coated urea), application rates (34, 68, 136, and 272 kg N ha ―1 ), and an untreated check (0 N) on wheat (Triticum aestivum L.) grain yield, soil pH, exchangeable base cations, and Al saturation. For the soil properties evaluated, significant differences among the different N sources did not exist after 30 annual applications of N fertilizer. The long-term N fertilization significantly reduced soil pH in the surface soil layer (0-15 cm), especially at the higher application levels. Soil pH decreased with time and was significantly related to the amount of total N applied for each N source. Nitrogen fertilization with each N source significantly increased exchangeable Al and Al saturation (Al sat ) but decreased exchangeable base cations (Ca 2+ and Mg 2+ ). Both exchangeable Al and Al sat increased with increasing N rate and were inversely related to soil pH. Despite decreased soil pH levels to

The potential of six industrial by-products for use as phosphorus-sorbing materials (PSMs) in solutions was evaluated. These included two different acid mine drainage treatment residuals (AMDR1 and AMDR2), water treatment residual (WTR), fly ash, bauxite mining residual, and flue gas desulfurization product (FGD). Characterization of the by-products and their mechanisms for sorption and retention of inorganic phosphorus (P) from solution identified those PSMs that sorbed primarily by an iron and aluminum (Fe/Al) mechanism, those that sorbed primarily by a calcium and magnesium (Ca/Mg) mechanism, and those that sorbed by both mechanisms. Degree of P sorption and associated mechanisms were strongly influenced by the pH, buffer capacity, ionic strength, and common ion effects.

Models for contaminant transport in streams commonly idealize transient storage as a well mixed but immobile system. These transient storage models capture rapid (near-stream) hyporheic storage and transport, but do not account for large-scale, stage-dependent interaction with the alluvial aquifer. The objective of this research was to document transient storage of phosphorus (P) in coarse gravel alluvium potentially influenced by large-scale, stage-dependent preferential flow pathways (PFPs). Long-term monitoring was performed at floodplain sites adjacent to the Barren Fork Creek and Honey Creek in northeastern Oklahoma. Based on results from subsurface electrical resistivity mapping which was correlated to hydraulic conductivity data, observation wells were installed both in higher hydraulic conductivity and lower hydraulic conductivity subsoils. Water levels in the wells were monitored over time, and water samples were obtained from the observation wells and the stream to document P concentrations at multiple times during high flow events. Contour plots indicating direction of flow were developed using water table elevation data. Contour plots of total P concentrations showed the alluvial aquifer acting as a transient storage zone, with P-laden stream water heterogeneously entering the aquifer during the passage of a storm pulse, and subsequently re-entering the stream during baseflow conditions. Some groundwater in the alluvial floodplains had total P concentrations that mirrored the streams' total P concentrations. A detailed analysis of P forms indicated that particulate P (i.e. P attached to particulates greater than 0·45 µm) was a significant portion of the P transport. This research suggests the need for more controlled studies on stage-dependent transient storage in alluvial systems. Copyright © 2011 John Wiley & Sons, Ltd.

Agricultural drainage ditches can provide a direct connection between fields and surface waters, and some have been shown to deliver high loads of phosphorus (P) to sensitive water bodies. A potential way to reduce nutrient loads in drainage ditches is to install filter structures containing P sorbing materials (PSMs) such as gypsum to remove P from ditch flow. The objective of this study was to determine the effect of land-application of gypsum removed from such filters on soil P forms and concentrations. Gypsum was saturated at two levels on a mass basis of P and applied to two soils of contrasting texture, a silt loam and a sandy loam and applied at both a high and low rate. The treated soils were incubated in the laboratory at 25˚C, and samples were collected at 1, 7 and 119 days after initiation. Soil type, time after application, gypsum rate, and P saturation level all had a significant impact on soil P forms and concentrations. However, it appears that land application of spent filter gypsum at realistic rates would have little effect on soluble P concentrations in amended soils.

Reducing phosphorus (P) loads from soils to surface waters is necessary for solving the problem of eutrophication. Many industrial by-products have been shown to sorb appreciable amounts of dissolved P from solution and it has been proposed to use P sorption materials (PSMs) such as steel slag in landscape scale “filters” for trapping dissolved P in runoff. The objective of this study was to model the effect of retention time (RT) and P concentration on P sorption by steel slag and a surface modified slag in a flow-through system. Sorption of P onto steel slag and rejuvenated-modified steel slag was measured using a traditional batch isotherm and a flow-through setting at several RTs and P concentrations. Flow-through data were used to produce a model that estimated P sorption based on RT and P concentration. The model was tested on a pilot-scale pond filter consisting of the same slag materials. For both the materials, flow-through tests indicated an increase in RT increased P removal efficiency but decreased the total amount of P removed at saturation. The Langmuir model developed from batch isotherms overestimated and underestimated P sorption in normal and rejuvenated slag respectively, relative to flow-through. Normal and rejuvenated slag removed 38 and 36% of P in the pilot-scale pond filter after 2 weeks of pumping. The Langmuir equation poorly predicted P sorption in the pond filter while the flow-through model produced reasonable estimates. Results suggest that flow-through methodology is necessary for estimating P sorption in the context of landscape P filters.

Zeolite minerals are ideal for removing ammonium nitrogen (NH4(+)-N) from animal wastes, leachates, and industrial effluents. The objectives of this study were to compare NH4+ removal and kinetics among several commercially available zeolites under various conditions and determine if calorimetry could provide information regarding kinetics of NH4+ removal. Ammonium sorption onto potassium (K) saturated zeolites was compared using synthetic vs. natural swine effluent and with either traditional batch-shaken system or a "tea bag" approach in which zeolites were contained in a mesh sack and suspended in a solution of swine effluent. Ammonium sorption was measured at four retention times using a flow-through system, and the resulting heat response was measured using isothermal calorimetry. Ammonium removal was not significantly different in synthetic vs. natural swine effluent. Ammonium removal was lower in batch-stirred compared to batch-shaken systems, suggesting that diffusion between particles was rate-limiting in the former system. Flow-through cells possessing contact times > 100 s displayed greater NH4+ sorption than batch systems, suggesting that maintaining high NH4+ concentration in solution, removal of exchange products, and sufficient reaction time are critical to maximizing NH4+ removal by zeolites. Within 100 s after NH4+ addition, endothermic heat responses indicated that NH4(+)-K+ exchange had peaked; this was followed by significant heat rate reduction for 50 min. This confirmed findings of an initial fast NH4(+)-K+ exchange followed by a slower one and suggests the 100-s period of rapid reaction is an indicator of the minimum flow through retention time required to optimize NH4+ sorption to zeolites used in this study.

Field experiments were conducted to evaluate the effects of repeated annual manure applications on sodium adsorption ratios and electrical conductivity in semi-arid environments. Swine effluent, beef manure, and anhydrous ammonia were annually applied at loading rates of 0, 56, 168, and 504 kg nitrogen (N) ha−1 to an irrigated, conventionally tilled, continuous corn (Zea mays L.) cropping study in the Oklahoma panhandle. Sodium adsorption ratios increased with swine effluent additions at the high N loading rate application; however, sodium adsorption ratio decreased with the high anhydrous ammonia loading applications and remained unchanged with beef manure applications. Linear correlations were found for swine effluent and anhydrous ammonia applications when N levels increased. Electrical conductivity levels increased 2.35 dS m−1 with the high anhydrous ammonia loading rate to a level where relative yields for crop production may be at risk of being reduced 50%.

SUMMARY AND CONCLUSIONS Isothermal titration calorimetry provided some indication of the P retention potential of 28 Oklahoma bench-mark soils. Th ere may have been some interference, however, with carbonate dissolution. While the heat of the fi rst titration indicated the degree of P retention, the characteristics of the heat patterns and thermograms (i.e., the endotherm category) may have provided some insight into P retention mechanisms. Based on the results of this study and others (Penn and Warren, 2009; Rhue et al., 2002; Miltenburg and Golterman, 1998), exother-mic peaks occurring from the addition of inorganic P solutions (NaH 2 PO 4 ) to soils indicated acid–base neutralization reac-tions (carbonate dissolution), ligand exchange of P onto Al (and also Fe) minerals, and Ca phosphate precipitation. Endothermic peaks indicated Al and Fe phosphate precipitation, evidenced by pure solution titrations and acid soils showing more endotherm characteristics than the neutral and alkaline soils. Th is confi rms previous studies (Penn and Warren, 2009; Rhue et al., 2002).Unlike the heat of the fi rst titration, endothermic charac-ter (i.e., endotherm category) provided no information on the amount of P retention. Based on the results of this study, the use of heat patterns, thermograms, and subsequent classifi cation into an endotherm category for P additions to soils should be restricted to qualitative interpretation with regard to discerning P retention mechanisms. Th e major limitation of this technique for assessing P retention in soils is mainly due to the fact that the dissolution of carbonates displays an exothermic signal that may mask endothermic signals and overlap with exotherms pro-duced from ligand exchange and Ca phosphate precipitation. Th erefore the technique would probably be improved if the P solution used in the titrations was adjusted to a pH equal to the soil being tested.Th e carbonate dissolution phenomenon also suggests the potential for the development of an ITC method for estimating soil carbonate content due to the highly exothermic nature of carbonate dissolution. Another possibility might be the develop-ment of an ITC method for estimating the surface area of a soil. Titration with a sorptive such as ethylene glycol monomethyl ether (EGME), which is used in surface area analysis, would probably produce a heat signal on sorption to the soil surface. Such a heat signal could be related back to true measurements of EGME retention. Essentially, any reaction resulting in signifi -cant heat change, with little heat from side reactions, can poten-tially be monitored using ITC or fl ow-through calorimetry. Th is makes calorimetry a real-time indicator of reaction processes, as opposed to traditional methodologies of taking discrete mea-surements before and aft er equilibrium.

For sorbing contaminants, transport from upland areas to surface water systems is typically considered to be due to surface runoff, with negligible input from subsurface transport assumed. However, certain conditions can lead to an environment where subsurface transport to streams may be significant. The Ozark region, including parts of Oklahoma, Arkansas, and Missouri, is one such environment, characterized by cherty, gravelly soils and gravel bed streams. Previous research identified a preferential flow path (PFP) at an Ozark floodplain along the Barren Fork Creek in northeastern Oklahoma and demonstrated that even a sorbing contaminant, i.e., phosphorus, can be transported in significant quantities through the subsurface. The objective of this research was to investigate the connectivity and floodplain-scale impact of subsurface physical heterogeneity (i.e., PFPs) on contaminant transport in alluvial floodplains in the Ozarks. This research also evaluated a hypothesis that alluvial groundwater acts as a transient storage zone, providing a contaminant sink during high stream flow and a contaminant source during stream baseflow. The floodplain and PFP were mapped with two electrical resistivity imaging techniques. Low-resistivity features (i.e., less than 200 O-m) corresponded to topographical depressions on the floodplain surface, which were hypothesized to be relict stream channels with fine sediment (i.e., sand, silt, and clay) and gravel deposits. The mapped PFP, approximately 2 m in depth and 5 to 10 m wide, was a buried gravel bar with electrical resistivity in the range of 1000 to 5000 O-m. To investigate the PFP, stream, and groundwater dynamics, a constant-head trench test was installed with a conservative tracer (Rhodamine WT) injected into the PFP at approximately 85 mg/L for 1.5 h. Observation wells were installed along the PFP and throughout the floodplain. Water table elevations were recorded real-time using water level loggers, and water samples were collected throughout the experiment. Results of the experiment demonstrated that stream/aquifer interaction was spatially non-uniform due to floodplain-scale heterogeneity. Transport mechanisms included preferential movement of Rhodamine WT along the PFP, infiltration of Rhodamine WT into the alluvial groundwater system, and then transport in the alluvial system as influenced by the floodplain-scale stream/aquifer dynamics. The electrical resistivity data assisted in predicting the movement of the tracer in the direction of the mapped preferential flow pathway. Spatially variable PFPs, even in the coarse gravel subsoils, affected water level gradients and the distribution of tracer into the shallow groundwater system.

The mechanism of P sorption onto soils has a strong impact on bioavailability and transport potential. Assessment of sorption energy via isothermal titration calorimetry (ITC) can potentially provide information on P sorption mechanisms. This study used ITC to examine P sorption onto poorly crystalline Georgia kaolinite at pH 4.3 and 6.3. A complementary sorption and desorption isotherm was also conducted at the same kaolinite/solution ratio as the titration experiment. In addition, other ITC experiments were performed to help interpret the kaolinite-P thermograms. Thermograms (measured heat response) for titration of P into pH 4.3 kaolinite indicated initial fast exothermic followed by slower endothermic reactions; both reactions decreased with further P additions. By the eighth titration, the net reaction turned from exothermic to endothermic, indicating that the endothermic reaction now dominated. The complementary sorption isotherm indicated a statistically significant "breakpoint" at this same P addition. In contrast, pH 6.3 kaolinite exhibited only exothermic reactions during P titrations. Based on sorption isotherms, solution thermodynamic modeling, and supporting ITC experiments, the exothermic reaction indicated P sorption onto kaolinite by ligand exchange and dissolution or protonation of kaolinite while the endothermic reaction indicated Al phosphate precipitation. Sequential desorption isotherm results showed that although the pH 4.3 and 6.3 kaolinite desorbed the same amount of P when normalized for initial surface P concentrations, kaolinite at pH 4.3 desorbed P at a greater rate than at pH 6.3. Compared with traditional solid-state techniques, ITC provides continuous data collection as reactions are occurring, rather than discrete observations.

Manure additions beyond crop P needs result in accumulated soil Ca phosphate (Ca-P). Although stable near neutral pH levels, there is concern about the solubility of accumulated soil Ca-P when soil pH conditions become acidic, potentially releasing water-soluble P (WSP). The purpose of this study was to examine changes in WSP among non-acidic, Ca-P-accumulated soils in response to six levels of acidification and acidification timing. Two soils that historically received excessive dairy manure were incubated for 8 wk with pH adjusted by single-point or gradual acid additions. After 8 wk, acid additions ceased and WSP, Mehlich-3 P (M3-P), and pH were determined before continuing the incubation for two additional weeks. Soil pH had little effect on M3-P, while acidification timing interacted with the effect of pH on WSP concentrations. After 8 wk, single-point acidification resulted in WSP decreases with decreasing pH, but gradual acidification showed the opposite effect in the pH range 4,5 to 6.5. This effect disappeared after two additional weeks of incubation, resulting in overall decreased WSP concentrations. Results suggested that among the high-P (Ca-P) soils used in this study, which contained significant Fe and Al, acidification did not increase WSP beyond the original concentrations since dissolved Ca-P was resorbed onto soil Fe and Al. This subsequent resorption of P was not immediate, however, and was dependent on kinetics. Overall decreases in soil WSP resulting from acidification is beneficial to water quality through prevention of nonpoint dissolved P losses from soils to surface waters.

Despite concerns that traditional soil sampling strategies are insufficient for assessing risk of surface water P contamination, there is no consensus that changes to these strategies, such as spatially explicit or discrete soil sampling within a field, represent enough of an improvement to justify the added cost. We conducted a study on four fields located on two dairy farms in Delaware County, New York, to characterize the spatial variability of P, Ca, Mg, Al, and Fe within two pastures and two hay fields at a 10-m scale and to interpret soil test P distribution relative to landscape and cultural practices. Pasture P distribution was characterized by various P "hot spots" that may be indicative of manure deposits by grazing animals. Hay fields contained large areas with elevated P relative to the rest of the field, with high-P areas occurring mostly near the gate and road where manure applications would be most accessible. Differences in soil properties associated with different soil map units also appear to partially explain P and Fe distributions in the mixed hay field. Results from a rainfall simulation study suggest that the use of a composite sampling strategy or an average P value for an entire field can potentially mask soil test P patterns such as those in the hay fields and result in an inaccurate estimation of P losses to surface waters. However, a composite sampling strategy may give a better estimation of P losses from pastures with "hot spots" because of the compositing effect whereby soluble P concentrations are affected by sorption processes that are controlled by low-P sediments.

The relationship between STP (soil test P) and DRP (dissolved reactive P) in runoff has been shown to vary with soil type due to differences in soil properties. The purpose of this study was to determine if soil tests could indirectly take into account differences in soil properties and thus provide one relationship with STP and runoff DRPamong a variety of soil types. Nine different soil types were sampled from four different fields to provide a range in STP. Unamended soils were packed into runoff boxes for use in a rainfall simulation study. All soils were analyzed for P, Al, and Fe using various extractions, and correlated to runoff DRP concentrations from all soils when grouped based on soil type and physiographic region. Slopes and intercepts were unique to soil type for the STP vs. runoff DRP relationship among all soil P tests except for WSP (water-soluble P) slopes, resulting in an overall universal slope of 0.0125 mg DRP L 21 , which agrees with past studies. The y intercepts from the soil WSP vs. runoff DRP relationship were well related to soil clay content (negative relationship) in addition to the fact that Coastal Plain soils had a significantly greater y intercept than Piedmont and Ridge and Valley soils when grouped by physiographic region. This suggests that Coastal Plain soils possess a greater potential for releasing DRP into runoff compared with Ridge and Valley and Piedmont soil at equivalent WSP values. This study provides a means with which to estimate potential runoff DRP concentrations by use of soil WSP and clay content.

Soil incubations are a common practice typically employed in assessing the effect of some treatment on the availability and solubility of phosphorus (P). However, standard sample preparation (drying and sieving) can alter soil chemical and physical properties, resulting in possible changes in P behavior upon soil incubation. Sixty surface soil samples were collected, air dried, and sieved before being incubated at field capacity for 7 days. After incubation, soils were allowed to air dry and were analyzed along with nonincubated samples for pH and water- and Mehlich-3-extractable elements. Incubation increased pH and decreased water-soluble P, calcium (Ca), and magnesium (Mg) relative to nonincubated soils. Increases in pH may have been due to increased solubility of residual calcium carbonates by drying and sieving. This increase in pH among soils with sufficient levels of P, Ca, and Mg resulted in the formation of Ca and Mg phosphates as confirmed by chemical speciation modeling.

the relationship between some measure of soil P and runoff dissolved P (Gburek et al., 2000; Coale et al., The relationship between soil test P (STP) and dissolved reactive 2002; Vadas et al., 2002). However, recent research has P (DRP) in runoff has been shown to vary with soil type due to differences in soil properties. This study was conducted to determine shown that this relationship will vary based on soil type the effect of mineralogy on P sorption behavior and DRP losses in (Sharpley, 1995; Sharpley et al., 1996; Pote et al., 1999; runoff using simulated rainfall. Nine different soil types were sampled Torbert et al., 2002). Therefore, an understanding of from four different fields to provide a range in STP. Unamended soils how different soil properties affect P concentrations in were packed into runoff boxes for use in a rainfall simulation study solution, leachate, and runoff is necessary to determine (7.5 cm h 1 for 30 min). A mineralogical analysis and adsorption- the effect of soil type on the relationship between STP desorption isotherm was conducted on one representative sample and runoff P losses. from each soil type. Results indicated that P retention for adsorption One of the most influential soil properties in regard and desorption in separated clay fractions and whole soils was well to P sorption is soil clay content, which has often been correlated to Al bearing minerals such as hydroxy-interlayered-vercorrelatedtoPsorptionparameters(FoxandKamprath, miculite (HIV), gibbsite, and amorphous Al. However, P retention was negatively related to kaolinite content, which was also confirmed 1970; Loganathan et al., 1987; Solis and Torrent, 1989; by isotherms conducted on pure clay minerals. Based on the isotherm Bennoah and Acquaye, 1989). However, it is the high results, all soils were split into two groups based on the ratio of HIV/ surface area and presence of various P sorbing minerals kaolinite. Soils with a HIV/kaolinite ratio 0.5 had a significantly that results in the common observation that high clay lower concentration of DRP in runoff for a given soil water soluble soils often adsorb more P compared with coarse-texP level compared with soils with a ratio 0.5. turedsoils(Loganathanetal.,1987).Phosphatesorption is attributed primarily to ligand exchange reactions between hydroxyls exposed on surfaces of minerals and P

Phosphorus lost from agricultural soils has been identified as a nonpoint source pollutant of surface waters in Delaware and throughout the Mid-Atlantic Coastal Plain. The Field Hydrologic and Nutrient Transport Model (FHANTM) 2.0 can help identify areas with a high potential for P loss, but the method used to estimate P concentrations in runoff waters needs reevaluation. The equation P d = KP o t α W β has been proposed to predict P desorption from soil to runoff. To test this equation for use in Delaware and the Mid-Atlantic Coastal Plain, we conducted rainfall simulations for 14 Delaware and Maryland soils packed into 5 by 20 by 100 cm boxes at a rainfall intensity of 7.5 cm h -1 and a slope of 5% for 30 min. We collected all runoff and measured an average soluble P concentration in runoff for the entire simulation. We predicted P concentrations using the above equation and compared them with measured values. Predicted values were well correlated to measured values (r 2 = 0.78), but P concentrations were overpredicted by an average of 20 times. After we added a calibration factor to the equation based on the amount of sediment lost in runoff during the rainfall simulation, measured and predicted soluble P concentrations exhibited a nearly 1:1 relationship. Results suggest that eroded sediment in runoff may resorb P from the runoff solution, causing the desorption equation to overpredict soluble P concentrations in runoff.

Continuous addition of municipal biosolids to soils based on plant nitrogen (N) requirements can cause buildup of soil phosphorus (P) in excess of crop requirements; runoff from these soils can potentially contribute to nonpoint P pollution of surface waters. However, because biosolids are often produced using lime and/or metal salts, the potential for biosolids P to cause runoff P losses can vary with wastewater treatment plant (WWTP) process. This study was conducted to determine the effect of wastewater treatment process on the forms and amounts of P in biosolids, biosolids-amended soils, and in runoff from biosolids-amended soils. We amended two soil types with eight biosolids and a poultry litter (PL) at equal rates of total P (200 kg ha(-1); unamended soils were used as controls. All biosolids and amended soils were analyzed for various types of extractable P, inorganic P fractions, and the degree of P saturation (acid ammonium oxalate method). Amended soils were placed under a simulated rainfall and all runoff was collected and analyzed for dissolved reactive phosphorus (DRP), iron-oxide-coated filter paper strip-extractable phosphorus (FeO-P), and total phosphorus (EPA3050 P). Results showed that biosolids produced with a biological nutrient removal (BNR) process caused the highest increases in extractable soil P and runoff DRP. Alternatively, biosolids produced with iron only consistently had the lowest extractable P and caused the lowest increases in extractable soil P and runoff DRP when added to soils. Differences in soil and biosolids extractable P levels as well as P runoff losses were related to the inorganic P forms of the biosolids.

Phosphorus (P) is a critical nutrient for plant growth in agriculture, but is also responsible for surface water enrichment that leads to toxic algal growth. While P loading to surface waters has traditionally been thought to occur from surface runoff, contributions from subsurface transport can also be significant. While P transport through many soil types is well-documented, the presence of highly conductive gravel outcrops and macropore networks can have a significant, yet poorly-documented effect on P movement to the aquifer. Floodplain soils in the Ozark ecoregion generally contain coarse chert gravel layers that exhibit macropore behavior. Previous research has evaluated short-term P transport in plot trials ranging from 1 m 2 to 100 m 2 across many Ozark ecoregion floodplain sites. Traditional methods of estimating P loading and soil saturation do not account for macropore flow and likely underestimate P transport to the water table. To address this concern, long-term P modeling was performed in HYDRUS-2D/3D using data collected from short-term plot experiments. Calibration was performed using single- and dual-porosity models with both homogeneous and heterogeneous gravel profiles. The dual-porosity model with heterogeneous hydraulic conductivity best matched experimental data, although the dual-porosity model with homogenous soil layers also performed well. Long-term P transport to a 3 m-deep water table was simulated using 9 years of both daily and 5 minute rainfall data with a P flux consistent with yearly poultry litter applications. Long-term simulations with 5 minute rainfall data found that 113 kg ha -1 reached the water table over 9 years, or 21% of P applied.

Soil fertility and plant nutrition is an applied science that integrates knowledge across all disciplines of soil and plant sciences to effectively and efficiently provide nutrients to plants. Efficient use of nutrients is required not only to maximize agricultural production but also to protect air, soil, and water quality as well as the natural resources involved in providing fertilizers to support agricultural production. This article provides an overview of the essential nutrients, their role in plant growth, behavior in soil, and management in crop production systems.

Several industries produce by-products capable of sorbing phosphorus (P) that are typically placed in a landfill. These P sorbing materials (PSMs) can reduce soluble P concentrations when added to animal manure, thereby reducing the potential for non-point P transport to surface waters after land application of the manure. Addition of PSMs to manure also provides a beneficial re-use for the by-product material. This chapter reviews and discusses the use of PSMs as manure amendments to reduce soluble P concentrations. The by-product PSMs can generally be separated chemically into two groups: iron/aluminum and calcium/magnesium. However, the ability of a PSM to reduce manure soluble P concentrations is a function of the chemistry of both the PSM and the receiving manure.