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Sugarcane mill mud/filter cake is an activated sludge-like byproduct from the clarifier of a raw sugar production factory, where cane juice is heated to ≈90°C for 1–2 hr, after the removal of bagasse. Mill mud is enriched with organic carbon, nitrogen, and nutrient minerals; no prior report utilized 16S rRNA gene sequencing to characterize the microbial composition. Mill mud could be applied to agricultural fields as biofertilizer to replace or supplement chemical fertilizers, and as bio-stimulant to replenish microorganisms and organic carbon depleted by erosion and post-harvest field burning. However, mill mud has historically caused waste management challenges in the United States. This study reports on the chemical and microbial (16S rRNA) characteristics for mill muds of diverse origin and ages. Chemical signature (high phosphorus) distinguished mill mud from bagasse (high carbon to nitrogen (C/N) ratio) and soil (high pH) samples of diverse geographical/environmental origins. Bacterial alpha diversity of all sample types (mill mud, bagasse, and soil) was inversely correlated with C/N. Firmicutes dominated the microbial composition of fresh byproducts (mill mud and bagasse) as-produced within the operating factory. Upon aging and environmental exposure, the microbial community of the byproducts diversified to resemble that of soils, and became dominated by varying proportions of other phyla such as Acidobacteria, Chloroflexi, and Planctomyces. In summary, chemical properties allowed grouping of sample types (mill mud, bagasse, and soil-like), and microbial diversity analyses visualized aging caused by outdoor exposures including soil amendment and composting. Results suggest that a transient turnover of microbiome by amendments shifts towards more resilient population governed by the chemistry of bulk soil. [ABSTRACT FROM AUTHOR]

Poultry litter is applied to crop production land in the southern United States as a waste management strategy as it is a nitrogen-rich fertilizer and plentiful throughout the region. While litter is a known reservoir for human enteric pathogens including Salmonella enterica, little is known regarding pathogen prevalence, concentration, and common serotypes within the material. Litter from thirteen farms across four southern states was examined for Salmonella. Samples (n = 490) from six of the thirteen (46.2%) farms tested positive. Thirty-three samples out of 490 (6.7%) were Salmonella positive. Salmonella was ca. 95% less likely to be collected from stacked litter piles than from the poultry house floor or pasture, and every day increase in litter age reduced the likelihood of recovering Salmonella by 5.1%. When present, concentrations of Salmonella in contaminated poultry litter were variable, ranging from <0.45 to >280,000 MPN/g. The most prevalent serotypes found were Kentucky (45.5%), Kiambu (18.2%), and Michigan (12.1%). Salmonella Kentucky also had the greatest distribution and was found on 4 of the 6 (66.7%) positive farms. Results from this survey demonstrated that Salmonella prevalence and concentration in poultry litter is highly variable, and good agricultural practices are critical to safely use poultry litter as a soil amendment on fresh produce fields. [ABSTRACT FROM AUTHOR]

Although the maritime Pacific Northwest (PNW) is the only region of the United States suitable climatically for spinach seed production, the acidic soils are highly conducive to spinach Fusarium wilt caused by Fusarium oxysporum f. sp. spinaciae. A soil bioassay developed to quantify the risk of spinach Fusarium wilt in fields has been offered to seed growers annually since 2010. Soil sampled from growers' fields each winter was planted with highly susceptible, moderately susceptible, and partially resistant spinach inbred lines, and the plants rated weekly to calculate a Fusarium wilt severity index (FWSI) and the area under the disease progress curve (AUDPC). Results for 147 soils tested from 2010 to 2013 have been published. This study examined results for an additional 248 soils tested from 2014 to 2019 with the bioassay modified to include an option of agricultural limestone amendment to the soils tested. FWSI and AUDPC were affected significantly (p <.001) by the main effects of soil and spinach inbred line, and the interaction of these factors. Correlation analyses showed a range in degree of association of FWSI and AUDPC with spinach seed crop rotation duration and soil properties, depending on the spinach inbred line (r = −.255 to –.267, n = 172 soils with characteristics suitable for correlation analyses). Stepwise regression models for 172 soils with relevant parameters for regression analyses identified spinach seed crop rotation interval, rate of agricultural limestone amendment, soil pH, and soil Fe, Mn, and Zn concentrations as most strongly associated with FWSI and AUDPC. However, the models accounted for ≤33.4% (R2) of the variability in Fusarium wilt risk. The soil bioassay remains a primary tool for spinach seed growers to select fields with low risk of Fusarium wilt. [ABSTRACT FROM AUTHOR]

Salinity stress is among the major abiotic stresses prevailing in arid and semiarid areas such as the southern high plains of the United States. In these areas, both declining quality of groundwater and cultivation practices have resulted in increased accumulation of salts in the root zone. The occurrence of excessive salts in the root zone is detrimental for plant growth and economic yield. Recently, biochar has received a great consideration as a soil amendment to mitigate the detrimental impacts of salinity stress. However, the effectiveness of biochar to mitigate the salinity stress depends on the feedstock type, pyrolysis temperature and time, soil type and properties, and plant species. Therefore, a pot experiment in a greenhouse was conducted to 1) examine the effects of salinity stress on physiology, shoot and root growth, and yield of eggplant (Solanum melongena L.), and 2) evaluate the potential of hardwood biochar and softwood biochar to mitigate the damaging effects of salinity stress on eggplant. The experiment was conducted in a split-plot design with three salinity levels of irrigation water [S0 (control, 0.04 dS·m-1), S1 (2 dS·m-1), and S2 (4 dS·m-1)] as main-plot factor and three biochar treatments [B0 (control, non-biochar), Bh (hardwood biochar), and Bs (softwood biochar)] as subplot factor with four replications. Results showed that stomatal conductance (gs) and photosynthesis rate decreased significantly, while leaf temperature and electrolyte leakage increased significantly with increase in irrigation water salinity levels. Root growth (root length density and root surface area density), shoot growth (plant height, stem diameter, and leaf area), and yield of eggplant declined with increase in levels of salinity stress. Biochar application helped to enhance gs and photosynthesis rate, and to decrease leaf temperature and electrolyte leakage in leaf tissues of plants. This resulted in better root growth, shoot growth, and fruit yield of eggplant in treatments amended with biochar than non-biochar (control) treatment. There was no significant difference in the effect of two types of biochars (hardwood and softwood biochar) on physiology, root growth, shoot growth, and yield of eggplant. Therefore, it can be concluded that softwood and hardwood biochars could be used to minimize the detrimental impacts of salinity stress in eggplant. [ABSTRACT FROM AUTHOR]

Approximately 200 million m3 of sediments are dredged every year in the United States. Of this amount, 2.3–9 million m3 are contaminated to the extent that they require special, and often costly, handling. Therefore, there is a pressing need to develop appropriate technology for the safe utilization of these sediments, especially in the case of the Hudson River, which is well known to demonstrate significant polychlorinated biphenyls (PCBs) contamination. Hence, the aim of the present study was to examine the influence of different doses of Hudson River sediments (10%, 25%, 50%, 75% and 100% admixtures) on soil quality and on the biochemical and growth response of cucumber (Cucumis sativus L. cv 'Wisconsin SMR 58'), used as potential phytoremediation tool for sediment-borne PCBs. A sediment/soil admixture was found to significantly decrease the nitrogen (N) content in the substratum; in addition, phosphorus (P) content was significantly increased by 50–100% sediment, while potassium (K) content was significantly increased by 10% sediment, and significantly decreased by >50% sediment. Although sediment treatment resulted in a gradual increase in PCB content in the soil-sediment substratum, exceeding the threshold effect concentration (TEC) for the ≥50% sediment admixture, the Microtox assay did not suggest toxicity to microorganisms. The results demonstrated also that admixture of 10–25% Hudson River sediment increased cucumber growth; however, higher doses led to growth inhibition, manifested as lower biomass and smaller leaves. Also, chlorophyll a and b content decreased with increasing doses of sediment. Phenylpropanoid and flavonol contents were significantly higher in plants grown in soil amended with 10% of sediment, but significantly lower in soil treated with a 100% sediment admixture. The anthocyanin content in plants was lower at admixtures of 50% and higher. The obtained results corresponded with the decreasing content of N and K. [ABSTRACT FROM AUTHOR]

Livestock manure is a common soil amendment for crop-livestock production systems. However, the efficiency of crop nitrogen (N) uptake from the manure-amended soil may not equate with that from inorganic N sources. The objective of this paper was to determine the efficiency of N uptake, grain yield, and total soil nitrogen (TSN) accumulation in beef manure-amended soil compared to the inorganic N fertilizer-amended soil. Data (1990–2015) from a long-term continuous winter wheat (Triticum aestivum L.) fertility experiment at Stillwater in Oklahoma, USA, were used in this report. Three of the six "Magruder Plot" treatments used in this study were manure, NPK plus lime (NPKL), and a check (no nutrients applied). Pre-plant N, P, and K were applied annually at 67, 14.6, and 27.8 kg·ha−1, respectively, while beef manure was applied every 4 years at 269 kg N·ha−1. The results indicated that grain N uptake in the manure treatment (48.1 kg·ha−1) was significantly (p<0.05) lower than that in the NPKL treatment (60.2 kg·ha−1). This represents 20.1% efficiency of inorganic N uptake than the manure N uptake. The average grain yield (1990–2015) from the manure and NPKL treatments was 2265.7 and 2510.5 kg·ha−1, respectively, and was not significantly different. There was a trend of TSN increase over the study period for both manure and NPKL treatments. The average TSN from manure and NPKL treatments was 0.92 and 0.91 g·kg−1 soil, respectively, and was not significantly different. While no significant difference between manure and NPKL grain yield was observed, there was a significantly lower uptake efficiency of manure N compared to inorganic N. Furthermore, the low uptake efficiency of the manure N could suggest a potential for environmental pollution. Appropriate timing and application rate of manure N sources could optimize crop use efficiency and limit potential threat to the environment. [ABSTRACT FROM AUTHOR]

Fresh produce outbreaks due to Shiga toxin-producing Escherichia coli (STEC) continue to occur in the United States (US). Manure-amended soils can pose a public health risk when used for growing raw agricultural commodities. Knowing the prevalence and concentration of STEC in untreated biological soil amendments of animal origin (BSAAO) is important to help guide the most appropriate pre-harvest interval(s) following application to limit risks from these soil amendments. Bovine manure samples were collected from 12 farms in Florida, including samples from piles, lagoons, barns, and screened solids. Two methods were used to detect stx1/2 and rfbE genes in samples. A prevalence rate of 9% for stx1 and/or stx2 and 19% for rfbE was observed from the 518 bovine manure samples evaluated. A most probable number (MPN) assay was performed on stx+ samples when applicable. The geometric mean for stx+ samples (n = 20) was 3.37 MPN g-1 (0.53 log MPN g-1) with a maximum value of 6,800 MPN g-1 (3.83 log MPN g-1). This research was part of a larger nationwide geographical study on the prevalence and concentration of STEC in bovine manure to help guide regulations on feasible pre-harvest intervals for the application of untreated BSAAO. [ABSTRACT FROM AUTHOR]

Coastal Plain soils of the southeastern United States are highly degraded, with low soil organic carbon (C), meager soil fertility, and poor soil structure. We tested the effectiveness of clay soil amendment to promote the formation of soil aggregates, improve organic C stability, and enhance nutrient availability in field. Subsurface clay soils (B horizon, 25% clay) were applied (∼25 T ha–1) to the top of the soil surface, followed by the planting of winter cover crop mixtures. Crop growth and nutrient uptake and relevant soil biogeochemical properties were analyzed at the end of the winter season. Additions of subsurface clay soils prompted the formation of water-stable macroaggregates (250–2000 mm) from 32 to 54% and increased mean weight diameter of the aggregates from 390 to 592 mm. Additions of subsurface clay soils increased clay content from 1.5 to 3.8% but did not change soil texture, pH, water holding capacity, and bulk density. The stock of dissolved organic nitrogen was not affected by the amendment, whereas nitrate leaching from field was reduced by 61% because of clay soil application. Clay soil additions inhibited the activities of C-cycling (N-acetyl-β-glucosaminidase, β-d-cellubiosidase, β-glucosidase, and β-xylosidase) and N-cycling (leucine aminopeptidase) enzymes but did not modify soil microbial community level substrate utilization patterns, resulting in a 63% reduction in C turnover rate and 19% increases in concentrations of labile organic C. Our results indicated that subsurface clay soil amendment can improve soil structure, nutrient availability, and the stability of labile C in the field, at least in the short term, and may be a promising management alternative to enhance the productivity and sustainability of the degraded Coastal plain soils. [ABSTRACT FROM AUTHOR]

Background and Aims: Phosphorus (P) is an essential nutrient for plants but its low availability often necessitates amendments for agronomical issues. Objectives were to determine P spatial distribution and speciation that remain poorly understood in cultivated soils. Methods: Aquic Argiudoll soil samples developed on a calcareous loam glacial till were collected from experimental plots submitted to contrasting crop rotations and amendments. Micro-X-ray fluorescence (μ-XRF) maps were collected on undisturbed samples. X-ray absorption near edge structure (XANES) spectra were collected on bulk samples and on fractions thereof, and on points of interests selected from μ-XRF maps. Results were compared with chemical analyses and extraction techniques results. Results: Chemical analyses show variations in total and exchangeable P contents depending on the samples but no significant difference is observed in terms of P distribution and speciation. P distribution is dominated by a low-concentration diffuse background with a minor contribution from minute hot spots. P speciation is dominated by phosphate groups bound to clay-humic complexes. No modification of P distribution and speciation is observed close to roots. Conclusions: This study evidenced minor effect of cropping and fertilizing practices on P speciation in cultivated soils. Despite analytical challenges, the combined use of μ-XRF and XANES provides relevant information on P speciation in heterogeneous soil media. [ABSTRACT FROM AUTHOR]

Each year, over 16 million tons of poultry litter is produced in the United States. Federal and state regulations now limit the amount of poultry litter that can be land-applied, making it difficult to store and dispose of poultry litter. The objective of this study was to evaluate composted poultry litter (CPL) as a fertilizer source for bedding plants at various rates in comparison with commercially available inorganic fertilizers in regard to plant growth and nutrient leaching. Two experiments were conducted to evaluate use of CPL as fertilizer for landscape annual bedding plants. Petunia spp. 'Celebrity Red' and Verbena hybrida 'Quartz Scarlet' were planted in raised beds simulating an urban landscape. Before planting, 10 inorganic fertilizer or CPL treatments were incorporated into the raised beds, including Peafowl® brand garden-grade fertilizer 13N-5.6P-10.9K (13-13-13) at rates of 4.9 g N/m² and 9.8 g N/m², Polyon®13N-5.6P-10.9K (13-13-13) at rates of 4.9 g N/m² and 9.8 g N/ m², and CPL at rates of 4.9 g N/m²,9.8 g N/m²,19.6 g N/m²,29.4 g N/m²,39.2 g N/m², and 49 g N/m². Use of CPL incorporated into landscape planting beds as a fertilizer source resulted in plants equal to or larger than plants grown with conventional inorganic fertilizers. Nitrate (NO3) and ammonia (NH4) levels in leachates from plots amended with CPL were comparable with plots amended with commercial inorganic fertilizers and nitrogen (N) levels were in most cases less in plots fertilized with CPL when compared with inorganic fertilizers when the same N rate was applied. Composted poultry litter may not be able to fully replace inorganic fertilizers, but it can reduce inorganic fertilizer requirements and provide an environmentally sound alternative to poultry waste disposal as well as provide beneficial aspects for plant growth in annual bedding plants. [ABSTRACT FROM AUTHOR]

This study investigated the biodegradation of the phthalate esters (PAEs) di-n-butyl phthalate (DBP) and di-(2-ethyl hexyl) phthalate (DEHP) in sludge and sludge-amended soil. DBP (100 mg kg-1) and DEHP (100 mg kg-1) were added to sewage sludge, which was subsequently added to soil. The results showed that sewage sludge can degrade PAEs and the addition of sewage sludge to soil enhanced PAE degradation. Sludge samples were separated into fractions with various particle size ranges, which spanned 0.1-0.45 μm to 500-2000 μm. The sludge fractions with smaller particle sizes demonstrated higher PAE degradation rates. However, when the different sludge fractions were added to soil, particle size had no significant effect on the rate of PAE degradation. The results from this study showed that microbial strains F4 (Rhodococcus sp.) and F8 (Microbacterium sp.) were constantly dominant in the mixtures of soil and sludge. [ABSTRACT FROM AUTHOR]

A majority of treated sewage sludge (biosolids) from U.S. wastewater treatment plants is applied to farmland as a soil amendment. Residents living close to treated farmland have reported becoming ill following land application of sludge. No systematic tracking or investigation of these reports or of land application practices that could affect off-site migration of chemical and biological constituents of the sludge has occurred, however. In the study described in this article, the authors conducted a web-based survey and phone interviews with officials at federal, state, and local regulatory and health agencies and municipal wastewater treatment plants for input on how to design and implement an investigation protocol for tracking and responding to reports of human illness near land application sites. Officials expressed a need for and interest in implementing a systematic, standardized investigation protocol and offered insights on aids and barriers to its use and collaboration among diverse agencies. Additional opinions and innovative solutions expressed in this article will assist interested users in the implementation of the investigation protocol. [ABSTRACT FROM AUTHOR]

Cropland best management practice recommendations often combine improvements to both tillage and fertilizer application practices to reduce sediment losses with surface runoff. This study evaluated the impact of conventional-till and no-till management practices with surface or deep-banded fertilizer application in sorghum-soybean rotation on runoff and sediment-yield predictions using the Soil and Water Assessment Tool (SWAT) model. The model was calibrated using USDA Natural Resources Conservation Service runoff curve number for antecedent moisture condition II (CNII), saturated hydraulic conductivity, and available water capacity parameters for runoff and USLE cropping factor (Cmin) for sediment-yield predictions for three field plots (0.39 to 1.46 ha [0.96 to 3.6 ac]) with different combinations of practices and validated for three field plots (0.40 to 0.56 ha [1.0 to 1.4 ac]) over a period of 2000 to 2004. Surface runoff calibration required CNII values greater than the recommended baseline values. No-till treatments required slightly greater curve number values than the till treatment, and this difference was similar to that associated with increasing the soil hydrologic group by one classification. Generally the model underpredicted the sediment yield for all management practices. Baseline Cmin values were adequate for treatments with soil disturbance, either by tillage or fertilizer deep-banding, but best-fit Cmin values for field conditions without soil disturbance (no-till with surface-broadcast fertilizer) were 2.5 to 3 times greater than baseline values. These results indicate current model limitations in modeling undisturbed (no-till) field management conditions, and caution that models calibrated for fields or watersheds predominated by tilled soil conditions may not function equally well in testing management scenarios without tillage. [ABSTRACT FROM AUTHOR]

Abstract: Land-based recycling of processed sewage sludge (biosolids) has traditionally been challenged by concerns over metals, organics, pathogens, odors, and public perception. Nutrient concerns, however, portend even greater challenges, and threaten land application programs in the US. Long-term application of biosolids results in accumulation of soil phosphorus (P) above concentrations needed for optimum crop yields. Water quality impairment associated with accelerated eutrophication is driving the US states to adopt policies and laws to reduce P losses to surface waters from agricultural land. Nearly all states have developed site assessment tools (P indices) to rank fields based on their vulnerability to P loss and to target remedial strategies. Biosolids have not been systematically addressed in most states and sustaining economical biosolids recycling programs will be difficult if policies fail to consider certain critical issues. Soil test P benchmarks should be based upon environmental P loss risk rather than crop response. Policies must recognize the role of mandated buffers in protecting surface water quality. Site indices must account for the sizable differences in P loss potential among biosolids types compared to mineral fertilizers and livestock manures. Finally, agronomic rate calculations must recognize different P fertilizer replacement values among biosolids products. Deployment of P management regulations for biosolids lacking scientifically defensible strategies in these areas will adversely affect land-based recycling. Sustainability requires additional research and intentional inclusion of biosolids in implementation of evolving P management policies. [Copyright &y& Elsevier]

The use and disposal of biosolids, or wastewater treatment sludge, as a fertilizer and soil amendment is becoming increasingly widespread. We evaluated the multiyear use of biosolids in apricot (Prunus armeniaca L.) production, grown on productive agricultural soils. Class A biosolids were initially applied annually at rates of 0, 1.9, 5.8, and 11.7 Mg · ha-1 (dry basis) to a 2-year-old apricot orchard on the USDA-ARS research site on the eastern side of the San Joaquin Valley, CA. These application rates provided estimated rates of 0 (control), 57, 170, and 340 kg total N · ha-1 yr-1, respectively. Compared to the control treatment, the applications of biosolids significantly increased soil salinity (electrical conductivity from 1:1 soil-water extract) and total concentrations of nutrients [e.g., calcium (Ca), magnesium (Mg), sulfur (S), phosphorus (P), zinc (Zn), and copper (Cu)] after 7 years but did not increase the concentrations of selected metals [cadmium (Cd), chromium (Cr), cobalt (Co), nickel (Ni), and lead (Pb)] between 0- and 60-cm soil depths. Mean concentrations of total nitrogen (N) and carbon (C) in soils (0- to 15-cm depth) ranged from a low of 1.3 g kg-1 to a high of 5.2 g · kg-1 and from 14.1 g · kg-1 to 45.7 g · kg-1 for the control and high biosolids treated soils, respectively. Biosolids applications did not lead to fruit yield reductions, although fruit maturation was generally delayed and more fruits appeared at picking times at the high rate of application. Yellow fruits collected from all biosolids applications were significantly firmer than were fruit collected from control trees, and they had higher concentrations of Ca, potassium (K), S, iron (Fe), and Zn in the fruit. Among the fruit quality parameters tested, the juice pH, total acidity, and fruit skin color were not significantly affected by biosolids applications. Malic acid concentrations decreased most of the time, while citric acid concentrations increased with increasing rates of biosolids applications. Overall, our results suggest that nonindustrial biosolids applied at an annual rate at or less than 11.7 Mg N · ha-1 (340 kg N · ha-1) can be safely used for apricot production on sandy loam soils. [ABSTRACT FROM AUTHOR]

A new garbage processing technology has been developed that sterilizes and separates inorganic and organic components of municipal solid waste. The non-composted byproduct of this process, Fluff®, has the potential to be utilized as a soil amendment to improve soil conditions in highly degraded soils. A study was initiated to evaluate Fluff as a soil amendment for establishing native grasses on disturbed US Army training lands. The Fluff was incorporated into a sandy loam soil at Fort Benning Military Reservation, GA on two sites: a moderately degraded and a highly degraded soil. The Fluff was incorporated at rates of 0, 18, 36, 72, and 143 Mg ha- 1 to assess the effects on soil properties for two growing seasons. The addition of Fluff improved available plant nutrients and soil pH levels at both sites. Also, Fluff reduced the level of soil bulk density and increased soil concentration of carbon (C) and nitrogen (N). Because no adverse environmental effects were detected and Fluff improved soil physical and nutrient conditions as well as improving perennial grass establishment with increasing application rates, land application of Fluff to degraded US Army training grounds could be considered a viable and beneficial alternative to current waste management practices. [ABSTRACT FROM AUTHOR]

Agriculture contributes considerably to water quality problems in the U.S. Tillage systems and land application of wastewaters from animal production facilities can increase both sediment and nutrient loadings to surface waters. Sediment transported to surface waters can decrease biodiversity and the usefulness of water for industry, drinking, and recreation. Anionic polyacrylamide (PAM) is a soil amendment that has been shown to reduce soil erosion during rainfall and irrigation. We hypothesized that dissolving PAM in land-applied lagoon effluent would reduce runoff and sediment loss in subsequent rainfalls. Swine wastewater from a third-stage anaerobic lagoon was mixed with high molecular weight PAM at concentrations of 0.10, and 20 ppm and then surface applied to a silt loam soil packed in erosion boxes. A rainfall simulator was used to study PAM's effectiveness at two slopes (4% and 8%) and two cover level (0% and 30%). Two consecutive storms with constant and varying rainfall intensity were simulated. PAM treatment reduced runoff from covered soils by up to 66%. On bare soil, the 10 ppm PAM treatment reduced first storm sediment losses by about 60%, while the 20 ppm PAM treatment resulted in about a 40% reduction. Lagoon effluent irrigation was found to produce higher sediment losses than water irrigation, but PAM treatment reduced sediment losses in lagoon-irrigated soils to levels that were comparable to water-only irrigations. These results indicate that application of anionic PAM with wastewater during surface irrigation can be an effective treatment to reduce runoff and erosion daring subsequent rainfall events. [ABSTRACT FROM AUTHOR]

We used tension disk infiltrometers to determine the hydraulic conductivity at the matric potential of -0.1 κPa (K-0.1), the immobile water fraction (θim/θ), and the mass exchange coefficient (α) in three soil profiles of an agricultural field cropped with winter wheat (Triticum aestivum L.). A significant effect of soil horizonation was found for K-0.1, θim/θ, and α and could be related to soil structure as determined either by tillage for surface horizons or by pedogenetic factors for subsurface horizons. The seedbed had lower K-0.1 values (31 to 99 mm h-1) than the plowed layer under the seedbed (94–430 mm h-1). The θim/θ was highly variable in the seedbed (0.213 to 0.882), while α had values ranging from 0.0006 to 0.0115 h-1. Values of θim/θ and α in the plow layer under the seedbed were similar but less variable than those found in the seedbed. In the subsoil, clay-enriched illuvial horizons had K-0.1 values similar to those found in the seedbed, but lower than those of the heavy clay horizon (average value of 260 mm h-1) and the limestone horizons (average value of 450 mm h-1). In the illuvial and heavy clay horizons, both θim/θ and α parameters had a small variability. In the limestone, we found a high variability of both θim/θ values (0.506–0.933) and α values (0.0006–0.0424 h-1) associated with high average values. The presence of subsoil horizons with large θim/θ and low α values may have a significant impact on ground water contamination. [ABSTRACT FROM AUTHOR]

Knowledge of the diffusion coefficient is necessary for modeling gas transport in soils and other porous media. This study was conducted to determine the relationship between the diffusion coefficient and pore structure parameters, such as the fractal dimension of pores (Dmp), the shortest path length through the medium (lmin), and the fractal dimension of the shortest path (Dmin). The finite element method (FEM) was used to simulate the gaseous diffusion process in an idealized soil system with a highly connected macropore network. The analysis was performed on binary images of soil thin sections. We show that the ratio ξ of the diffusion coefficient in soil (Deff) to that in free air (D0) is a function of not only the air-filled porosity ϵ, but also of other parameters, and hence no universal relationship exists between ξ and Dmp and Dmin. Furthermore, ξ is shown to be strongly related to the pore-space structure and the direction of the concentration gradient. The tortuosity (T) furthermore was found to be related to the weighted path length along the main diffusion direction. [ABSTRACT FROM AUTHOR]

Historic phosphorus (P) loading from agricultural areas has been identified as one of the major causes for ecological changes occurring in the Florida Everglades. The restoration plan for the Everglades includes construction of large stormwater treatment areas (STAs) to intercept and treat this relatively high nutrient water down to very low total P (TP) concentrations. One such STA has been in operation for approximately 10 yr and contains both emergent aquatic vegetation (EAV) and submerged aquatic vegetation (SAV) communities. The surface water TP concentrations in areas near the outflow range from 0.02 to 0.05 mg TP L-1. To simulate these areas, we investigated the interaction of vegetation type; EAV or SAV; and hydrology; continuously flooded or periodic drawdown; on the P removal capacity in mesocosms packed with peat soil obtained from STA-1W. The surface water had low TP concentrations with an annual mean = 0.023 mg L-1. For SRP and TP, hydrologic fluctuations alone had no discernable impact on P treatment while vegetation type showed a significant impact. Influent soluble reactive P (SRP) decreased by 49% for the SAV treatments compared with 41% for the EAV treatments, irrespective of hydrology treatment. The reduction of dissolved organic P (DOP) was also higher for the SAV treatment averaging 33% while showing a reduction of 11% for the EAV treatments. There was no significant difference in the treatment efficiency of particulate P (PP) across the treatments. For TP, SAV treatments removed 45% of TP while EAV removed significantly less at 34%. By mass calculations, the EAV required 85% more P for plant growth than was removed from the water column in 1 yr compared with only 47% for the SAV. Therefore, the EAV ‘mined’ substantially more P from the relatively stable peat soil, translocating it into the detrital pool. [ABSTRACT FROM AUTHOR]

The existing bulk density and wetness of a soil influence soil compaction, but the ability to quantitatively describe these effects is limited. The purpose of this study was to generalize an empirical nonlinear equation for uniaxial soil compression, presently limited to fitting one compression curve at a time, by adding a capability to describe a single soil material at variable initial bulk density and wetness. The original relationship between the compressed soil bulk density and the applied stress was first simplified by reducing the number of coefficients required to fit a single experimental curve from three to two. The generalized relationship combined the original equation, an equation that removed a high correlation that existed between two of its coefficients, and two equations that reflected the impact of the bulk density, water content, and matric potential on the two remaining coefficients. This generalized relationship was tested for soil materials at various initial bulk density, water content, and matric potential values where texture and organic matter content were held constant. The study used 21 datasets representing three to five horizons of four soils and one soil mixed with four different amounts of sand. For each horizon or soil material studied, the generalized relationship was fitted simultaneously using nonlinear regression to 2–14 compression curves per horizon, including disturbed and undisturbed soil samples in nine cases. The generalized relationship fit each dataset with an R² ≥ 0.932 (P < 0.001) and was judged superior to the best existing equation for multiple curves. [ABSTRACT FROM AUTHOR]

A previous study on costs and benefits of compost application in Florida (Rahmani et al. 1999) showed that compost can have positive monetary benefits; however, the various benefits and the scope of potential compost applications are not known by many users. Although composting a variety of organic wastes is thought to be an alternative to landfill use, in the long run, conversion of a part of organic solid wastes to compost will reduce the disposal problem only if a market with a continuous demand for compost develops, and leads to products moving out of the composting facilities and being used. Previous research indicated that compost was applied only for some crops and to a limited extent by growers in Florida. The results of a study evaluating compost users' and potential users' views regarding compost application in Florida are presented in this paper. The study involved a telephone survey of citrus growers, golf courses, landscaping service businesses, and ornamental plant growers in Florida. The survey questionnaire addressed issues such as problems experienced by compost users, sources of information about compost, barriers to using compost, and incentives for potential compost users. The survey explored the issues of concern and the attitudes of those who already use compost as well as non-compost users in Florida. From a list of 2,350 citrus, golf course, landscaping, and nursery businesses, 247 randomly selected businesses were interviewed. The results of the study suggest that in order to promote more widespread compost use, information and product quality are the key. All the other issues are part of or closely related to information and quality. Cost of compost application, availability and quality consistency, and the benefits of compost application are the crucial information that potential compost users want to have. To make compost a more widely used input in agriculture, more information needs to be disseminated and the quality of compost nee... [ABSTRACT FROM AUTHOR]

Abstract The effects of intensive recreation impacts and restoration amendments on soil parameters were assessed at four campsites in the Eagle Cap Wilderness, northeastern Oregon. Sites (2,215- to 2,300-m elevation) are characterized by shallow granitic soils, an Abies lasiocarpa /Pinus albicaulis overstory, and a Vaccinium scoparium understory. In fall 1995, plots were established at four campsites on three subalpine lakes in which soils were scarified, compost amended, and planted to native species. In summer 1998, we sampled surface soils (0–15 cm) on undisturbed sites (between and under vegetation) and unamended and compost-amended campsite soils. Samples were analyzed for total organic C, total N, potentially mineralizable N (PMN), NH4 , soil moisture, microbial biomass, basal 5-day respiration rates, and microbial community carbon utilization profiles. Unamended campsite soils had significantly lower levels of PMN, microbial biomass, basal respiration, and number of substrates metabolized in carbon utilization profiles. Compost addition elevated all these impacted parameters on campsite soils, although the increase in basal respiration rate was neither statistically significant nor sufficient to approach rates found underneath vegetation on undisturbed soils. Only the number of substrates metabolized in the carbon utilization profiles was significantly higher on compost-amended soils than on undisturbed soils. Levels of PMN indicate that campsite soils may lack sufficient N for rapid plant regeneration, whereas amended and undisturbed soils contained adequate quantities of available N. This work suggests that compost amendments can ameliorate impacts to soil chemistry and microbial populations caused by camping, without exceeding the N fertility found on undisturbed soils. [ABSTRACT FROM AUTHOR]

Determines the effects of soil amendment on sand-based sports turf media in Ames, Iowa. Uses of inorganic soil amendments; Addition of inorganic materials to sand-based golf green; Changes in the saturated hydraulic conductivity of the sand-inorganic mixtures; Inducement of saturated hydraulic conductivity by freezing and thawing.

Evaluates controls on nitrous oxide (N2O) emission in a Goldsboro loamy sand receiving field in North Carolina that was planted to winter wheat. Temporal changes in N2O efflux and soil physicochemical properties; Lower time-integrated N2O emission for plots amended with swine waste.

Best management practices (BMPs) are site-specific and their implementation, long-term management, and maintenance are important for successful reduction of phosphorus (P) loss into headwater streams. This paper reviews published research on managing P loss from agricultural cropping systems in the Midwestern United States and classified the available research based on BMPs and their efficacy in reducing P loss. This review paper also identifies the areas where additional research could provide insight for managing P losses. Our literature review shows that cover crops, reduced tillage, saturated buffers, and constructed wetlands are the most evaluated areas of current research. However, additional research is necessary on the site-specific area to measure the effectiveness of BMPs in managing P loss. The BMPs that serve as a sink of P need further evaluation in long-term field-scale trials. Studies evaluating adsorption and desorption mechanisms of P in surface and subsurface soils with materials or amendments that bind P in the soil are needed. The time required and pathways, where the flush of available P is lost or fixed in the soil matrix, need further investigation. Measured P loss from BMPs like bioreactors and saturated buffers supplemented with P adsorption materials or filters need to be simulated with models for their prediction and validation. Field evaluations of P index and critical source area concepts should be investigated for identifying problematic areas in the watersheds. Identification of overlapping areas of high P source and transport can help in strategic planning and layout, thereby resulting in reducing the cost of implementing BMPs at field and watershed scales. [ABSTRACT FROM AUTHOR]

The article examines nutrient cycles and nutrient inputs that are necessary for agricultural development, while evaluating the impact that these amendments may have on environmental quality and human health. Harvesting crops diminishes soil reservoirs of nitrogen and phosphorus, both of which must be replaced through additions of substances such as animal manure or mineral fertilizers. The authors discuss the nutrient balances of low-input corn in Kenya, high-input wheat and corn double-cropping systems in China, and corn-soybean rotations in the U.S.

The article discusses the report of the U.S. Agricultural Research Service (ARS) regarding the implication of fertilizer use in tillage to control greenhouse gases. A study conducted by Rod Venterea, an ARS soil scientist, revealed that tillage practices can increase emissions of more powerful greenhouse gases. It was also found that the spreading of urea nitrogen fertilizer pellets can cause higher oxide emissions.

Use of anionic polyacrylamide (PAM) as an erosion control soil amendment has been studied at the U.S. Department of Agriculture-Agricultural Research Service (USDA-ARS), National Soil Erosion Research Lab since the early 1990s. An initial field experiment in Indiana using simulated rainfall on a sloping silt loam soil found that 20 kg ha-1 of PAM could reduce sediment loss by more than 60% from the first storm event from an agricultural silt loam soil, as well as provide control from rill detachment for inflows of water up to 60 L min-1. More recent studies have examined use of PAM on areas prone to excessive erosion (highway embankments, landfill caps, etc.) to provide control while vegetation is being established. A simulated rainfall study found that 80 kg ha-1 PAM application on a 3:1 silt loam soil embankment reduced runoff by 86% and soil loss by 99% in a severe storm event (69 mm h-1 for 1 hour) on initially dry soil. The PAM continued to be effective at controlling runoff and soil loss through a series of simulated rainfall applications, reducing runoff by an average of 40% and soil loss by an average of 83% over the entire experiment. Two associated natural rainfall studies found similar erosion control benefits, as well as improved vegetation establishment. Polyacrylamide at 80 kg ha-1 was also found to be effective at preventing earthen channel erosion and degradation on a preformed trapezoidal channel at a 1% slope at inflows of water up to 760 L min-1. Application of PAM as a liquid spray that is allowed to dry on the soil surface is more effective than an application of dry PAM granules for immediate erosion control. Recent laboratory experiments have been targeted toward determining the optimal rates of PAM to control rill erosion and minimize cost. [ABSTRACT FROM AUTHOR]

In the spring of 2003, a grocery chain based in Richmond, Virginia, hopes to begin reaping the benefits of its left-over food waste--by selling it as compost. For several months, Ukrop's Super Markets, Inc., has been hauling fruit and vegetable residuals from its central processing facility to a nearby landscaping business, where the food scraps eventually decompose into a nutrient-rich compost. Both Ukrop's and Watkins Nursery, the partnering landscaping firm, draw significant benefits from the arrangement. Ukrop's saves $30 for each ton of food waste that does not go to a landfill, while it also expands on its environmental vision and produces a high-quality fertilizer for sale to its customers. So far, Ukrop's has nearly broken even in transportation costs with the elimination of some landfill fees.

The PC-based model for predicting tillage and crop rotation effects on organic carbon decomposition and storage in the soil as organic matter (OM) uses crop residue and root biomass production, tillage type and timing, and average temperature from existing c-factor files, created with the Revised Universal Soil Loss Equation (RUSLE). Residue nitrogen content and soil layering information--including layer thickness, organic matter content, and bulk density-- complete the input requirements for the model. Short-term trends of surface and remaining buried residue and long-term trends in soil organic matter content, are computed for individual fields and cropping practices. The model was calibrated with soil organic carbon observations (converted to equivalent OM values) from plots with over 60 years of recorded management history including wheat/fallow with manure additions and wheat/fallow with stubble removal. Computations have a 95% confidence interval of +/- 3.3 g OM kg-1 soil (0.33% OM). Comparison of OM calculations from the calibrated model with observed values from Lancaster, Wisconsin, and Lexington, Kentucky, produced mean residual errors ranging from -3.0 to + 0.2 g OM kg-1 soil (- 0.3 to + 0.02 % OM). [ABSTRACT FROM AUTHOR]

Features Davis Water & Waste Industries' Envirofab MiniMiser biosolids drying system designed to produce high-quality, nutrient-rich soil amendment products from biosolids. Specifications; Uses.