bluuebunny/crossref_metadata_2025 huggingface dataset:
Denitrification from Fescue Pastures in the Southeastern USA Fertilized with Broiler Litter
Authors: Marshall S. B. , Cabrera M. L. , Braun L. C. , Wood C. W. , Mullen M. D. , Guertal E. A.
Published: July 2010

Many aspects of the denitrification process in pasture ecosystems remain poorly investigated, especially as affected by application of animal manures. Denitrification can be, however, a major pathway of N loss from soil, decreasing efficiency of N fertilizers, as well as contributing to global warming and ozone depletion. We quantified N loss via denitrification from tall fescue (Festuca arundinacea Schreb.) pastures following fertilization with broiler litter. Study sites were located in the Coastal Plain (Alabama), Piedmont (Georgia), and Cumberland Plateau (Tennessee) Major Land Resource Areas of the southeast USA. Litter was applied to supply 70 kg of available N ha−1 based on equations developed by the USDA and the USEPA. Measurements were taken every 2 wk during the course of 2 yr (1995–1996 and 1996–1997) using an in‐situ acetylene‐inhibition technique. Denitrification flux was highly variable, ranging from −20 to 2500 mg N gas m−2 h−1. Total losses of N gas were all <6 kg ha−1 during 150 d after application, representing a loss of <5% of total N applied. Losses from treated plots were not significantly higher than those from control plots. Denitrification rates at these sites were not predictable by any one factor, but seemed to respond only to combinations of various factors such as soil temperature, soil NO3 concentration, and soil water content. Our results indicate that risk of N loss and atmospheric pollution due to denitrification from soils in the southeastern USA is not significantly increased by application of broiler litter at appropriate rates.
Storage and Handling Can Alter the Mineralization Characteristics of Manure
Authors: Van Kessel J. S. , Reeves J. B. , Meisinger J. J.
Published: July 2010

In vitro incubations of manure‐amended soil are frequently used to evaluate manure N and C availability. Manures are typically frozen, refrigerated, or dried prior to analysis. An experiment was designed to evaluate the effects of these manure storage methods on C and N mineralization characteristics. Two dairy slurries were collected and seven treatments, fresh, frozen (4 or 5 wk), refrigerated (1 d, 1 wk 4 wk), freeze‐dried or oven‐dried, were compared. Rates and extents of N and C mineralization were determined by aerobic incubation of slurry‐amended soil at 25°C. Slurry was added at a rate equivalent to 265 kg N ha−1 incorporated into the upper 15 cm of soil. The appearance of NH+4 and NO−3 and the production of CO2 were monitored during 16 wk. Refrigeration or freezing had no effect on slurry N content; however, freeze drying and oven drying resulted in N losses of 30% or more. CO2‐C production followed first‐order kinetics during 9 wk for all treatments with approximately 18 to 26% of the slurry C mineralized. Net mineralization of organic N was minimal in all treatments and was not affected by freezing or refrigerating the slurries. With oven‐dried and freeze‐dried slurries, however, there was a greater immobilization of N when compared with fresh manure. Results indicate that oven drying and freeze drying are unsuitable methods of storage, but the mineralization characteristics of manure are not affected by refrigeration or freezing.
Phosphorus Utilization and Excretion in Pig Production
Authors: Poulsen Hanne Damgaard
Published: July 2010

Phosphorus deficiency is known to result in depressed growth and bone abnormalities in pigs (Sus scrofa). As such, practical pig feeding recommendations have over the years aimed at ensuring that pigs would not suffer from P deficiency. This means that a large safety margin has normally been included into the P feeding recommendations in order to compensate for variation in P digestibility in feedstuffs and feed phosphates. However, increasing attention has been devoted to the utilization and excretion of P in pig production over the last decade. Because of the continuous accumulation of P in soil supplied with manure, P utilization and excretion is a matter of great concern, especially in intensive pig‐producing countries, but recent research has shown that it is possible to reduce the P content of manure without affecting pigs' health and productivity. Several aspects have to be addressed. First, it is necessary to identify the content of digestible P rather than total P, since this will give a more precise basis for determination of P requirements for each specific pig category (sows, piglets, and growing‐finishing pigs), allowing safety margins to be reduced. The introduction of digestible P will also enable pig farmers and feed manufacturers to formulate diets that contain the exact amount of digestible P needed by pigs. Phosphorus digestibility in feedstuffs of plant origin is often low, so another approach is to render the intrinsic P more available for pigs. This will reduce the necessity for the addition of extra P as inorganic feed phosphates to pig diets.
Reducing Phosphorus Runoff and Inhibiting Ammonia Loss from Poultry Manure with Aluminum Sulfate
Authors: Moore P. A. , Daniel T. C. , Edwards D. R.
Published: July 2010

Applications of aluminum sulfate (Al2(SO4)3 · 14H2O), commonly referred to as alum, to poultry litter have been shown to decrease P runoff from lands fertilized with litter and to inhibit NH3 volatilization. The objectives of this study were to evaluate the effects of alum applications in commercial broiler houses on: (i) NH3 volatilization (inhouse), (ii) poultry production, (iii) litter chemistry, (iv) P runoff following litter application. Two farms were used for this study: one had six poultry houses and the other had four. The litter in half of the houses at each farm was treated with alum; the other houses were controls. Alum was applied at a rate of 1816 kg/house, which corresponded to 0.091 kg/bird. Each year the houses were cleaned in the spring and the litter was broadcast onto paired watersheds in tall fescue at each farm. Results from this study showed that alum applications lowered the litter pH, particularly during the first 3 to 4 wk of each growout. Reductions in litter pH resulted in less NH3 volatilization, which led to reductions in atmospheric NH3 in the alum‐treated houses. Broilers grown on alum‐treated litter were significantly heavier than controls (1.73 kg vs. 1.66 kg). Soluble reactive phosphorus (SRP) concentrations in runoff from pastures fertilized with alum‐treated litter averaged 73% lower than that from normal litter throughout a 3‐yr period. These results indicate that alum‐treatment of poultry litter is a very effective best management practice that reduces nonpoint source pollution while it increases agricultural productivity.
Transfer of Phosphate Ions between Soil and Solution: Perspectives in Soil Testing
Authors: Morel C. , Tunney H. , Plénet D. , Pellerin S.
Published: July 2010

Phosphorus inputs must be estimated accurately to optimize the economic return to farmers and minimize P loss from soils to surface waters. Currently, P recommendations are based on the diagnosis of field crop responses by chemically extracted soil P. However, the inability of chemical extraction to characterize plant‐available P limits the reliability of these recommendations. Major sources of P mobilized by plant roots include P ions in solution and those from soil constituents, which replenish and buffer solution. A mechanistic evaluation of soil P supply should therefore be based on the description of P ion transfer between soil constituents and solution. Sorption, desorption, electro‐ultrafiltration (EUF), and isotopic exchange studies show that an adequate modeling of this quantity [Q(CP,t)] of P ions must account for both the concentration of P ions in soil solution (Cp) and time (t). In one long‐term field experiment, the Q(CP,t) description was not affected by crop rotation and mineral fertilization histories; therefore, Q(CP,t) changes are fully explained by CP changes. In two field experiments, CP changes were linearly correlated with the cumulative P budget, inputs, and outputs over years. In three field experiments, the soil type effect on the relative maize (Zea mays L.) response curve was taken into account using the ability of soil P to replenish solution P for 1 d. The residual variance of this diagnosis is halved compared to Olsen's extraction. Although more information is necessary, accuracy is improved when soil testing is based on mobility of P ions.
Integrating Soil Phosphorus Testing into Environmentally Based Agricultural Management Practices
Authors: Sims J. T. , Edwards A. C. , Schoumans O. F. , Simard R. R.
Published: July 2010

Soil testing has been an accepted agricultural management practice for decades. Interpretations and fertility recommendations based on soil analyses and the information obtained with soil samples on cropping systems, tillage practices, soil types, manure use, and other parameters have contributed to the increased efficiency of agricultural production. Recently, however, analyses of long‐term trends in soil test P values have shown that soil P in many areas of the world is now excessive, relative to crop P requirements. The role of P in the eutrophication of surface waters and emerging concerns about the human health impacts of toxic algal/dinoflagellate blooms have heightened public awareness of nonpoint source pollution by agricultural P. The greatest concerns are with animal‐based agriculture, where farm and watershed‐scale P surpluses and over‐application of P to soils are common. The need for nutrient‐management plans based on N and P is now an issue of intense debate in the U.S. and Canada. This paper addresses three issues: Should the applications of organic wastes and fertilizers be based on soil P and, if so, what is the most appropriate testing method to assess environmental risk? How can our knowledge of soil P chemistry be integrated with the expertise of hydrologists, agronomists, aquatic ecologists, and others to assess the risks that P in agricultural soils poses to surface waters? And, finally, how can we use soil P testing to evaluate new best management practices (BMPs) now being developed to reduce P transport from soil to water?
Some Aspects of Achieving Sustainable Phosphorus Use in Agriculture
Authors: Higgs B. , Johnston A. E. , Salter J. L. , Dawson C. J.
Published: July 2010

The management of P in agriculture must maximize the benefit to producers and minimize any adverse environmental effects. The latter arise from the loss of P from soil to standing freshwater. Even very small amounts of P can raise the concentration above the critical value for eutrophication. Such small quantities can be lost in eroded soil, in surface runoff and in drainage water. The relative importance of these pathways depends on many factors, including topography, rainfall, farming system, soil characteristics, and the bioavailability of the P that is lost. The success of agriculture in increasing food production to meet the increasing needs of humankind, especially since the 1950s, owes much to the use of P in fertilizers and animal feeds. What is now required is to ensure that P, a finite earth resource, is not wasted and that soils do not become so enriched with P that there is an unnecessary risk of too much P being carried to water from agricultural soils. The concept of taking account of critical soil P values to optimize the use of P in both fertilizer and manures is discussed here.
Development of an Indicator for Risk of Phosphorus Leaching
Authors: Hesketh N. , Brookes P. C.
Published: July 2010

Previous work showed that at soil P concentrations below 57 mg 0.5 M NaHCO3‐extractable P (Olsen P) kg−1 soil, little P was found in drainage waters collected from tile drains set 65 cm below the soil surface in soils from the Broadbalk Continuous Wheat Experiment. Above this soil P concentration (termed the Change‐Point) both total P and molybdate‐reactive P (MRP) in drainage waters were linearly related to soil Olsen P concentrations. We now need to know if the Change‐Point measured on Broadbalk occurs on other soils, and if so, whether a common value applies or if it varies depending upon soil type, management, and site hydrology. We investigated the possibility of 0.01 M CaCl2‐extractable P being an indicator of the Change‐Point. In all the soils studied, we found that the dynamics of P solubility in CaCl2 closely resembled the dynamics of P solubility in drainage waters of Broadbalk, since very distinct Change‐Points occurred under both conditions. However, Change‐Points measured following extraction with CaC2 varied widely between soils, from 10 to 119 mg Olsen P kg−1 soil. Lysimeter studies showed, with some exceptions, good agreement between Change‐Points measured in drainage water and in 0.01 M CaCl2. We therefore suggest that this approach may provide a valid indicator of the soil Olsen P concentration at which significant amounts of P begin to leach from soil to water, provided preferential pathways exist in the subsoil to permit P leaching down the soil profile in drainage water.
Assessing the Impact of Terrestrially Derived Phosphorus on Flowing Water Systems
Authors: Edwards A. C. , Twist H. , Codd G. A.
Published: July 2010

Recent efforts to quantify the terrestrial inputs and cycling of P in agricultural systems are allowing management strategies to be developed to minimize the loss of P. While this approach has had clear advantages for standing waters, potential benefits for flowing freshwater systems are more difficult to predict. As a consequence of the unidirectional and dynamic nature of flow in rivers, temporal and spatial separations between the source of P and the point of potential impact arc introduced when considering a whole watershed. The ability to quantify the residence time of P within any particular part of a river system is therefore essential so that the specific contribution of individual P sources to biological demand can be determined. The smaller algal biomass productivity measured in flowing, compared with standing, waters at a similar supply rate of P indicates the need to consider the roles of other watershed factors in modifying the relationship between growth and P supply. The site‐specific nature of responses to P suggests a need to develop a hierarchical classification system where individual river sections can be ranked according to their likely responsiveness to P. The ecoregion concept, combined with stream order, would integrate spatial and temporal aspects of gradient, land use, flow velocity, and water quality. For this to be successful, we must demonstrate a link between perturbations to the terrestrial P cycle, the delivery of P to flowing waters, and a biological impact.
Buffer Zones and Constructed Wetlands as Filters for Agricultural Phosphorus
Authors: Uusi‐Kämppä Jaana , Braskerud Bent , Jansson Håkan , Syversen Nina , Uusitalo Risto
Published: July 2010

Findings concerning P removal in buffer zones (BZs), constructed wetlands (CWs), and ponds in Finland, Norway, Sweden, and Denmark are presented in this paper because most such studies have been published only in Nordic languages. Retention of P was tested in 11 BZs, four CWs (less than 0.5‐m deep and vegetated with macrophytes), and seven ponds (deeper than 0.5 m). The grass buffer zone (GBZ) and vegetated buffer zone (VBZ) plots were compared with plots without a BZ; and P retention in CWs, ponds, and some BZs was estimated by subtracting total phosphorus (TP) mass in the outlet from TP mass in the inlet. Buffer zones decreased loads of TP from agricultural runoff water by 27 to 97% (0.24–0.67 kg ha−1 yr−1). The retention as a percentage increased with increasing BZ width. The BZ's upper part was, however, most effective in mitigating TP mass loads (1.6–4.4 g m−2), due to the importance of sedimentation as a retention process. The ponds and CWs reduced TP loads by 17 and 41%, respectively (2–116 g m−2 yr−1). The retention increased with the surface‐area/watershed‐area ratio. CWs were more effective in retaining TP than were ponds, possibly due to shallower depths and dense vegetation. The retention of dissolved reactive phosphorus (DRP) was inconsistent, both in BZs and in CWs. Vegetation should be harvested in BZs to decrease the DRP losses. Harvesting of vegetation is not recommended in CWs.
Prospects for Controlling Nonpoint Phosphorus Loss to Water: A UK Perspective
Authors: Withers Paul J. A. , Davidson Ian A. , Foy Robert H.
Published: July 2010

Accelerated losses of P from intensively managed farmland can contribute to eutrophication problems in fresh waters, and improved nutrient and land management practices may be required in sensitive watersheds to help maintain good water quality for a range of users. Control of background P losses caused by increases in soil P status require long‐term strategies to reduce surplus P inputs, since excessive soil P accumulation cannot be rectified quickly. However, targeted actions aimed at controlling the transport of soil P, and/or preventing the often significant losses of P that occur following the application of fertilizers and manures to the land surface, are needed to achieve the more short‐term reductions in P export required to overcome the effects of eutrophication. The challenge is to identify which mitigation options can be implemented most cost‐effectively under the operating site hydrological conditions. Prospects for control of nonpoint P loss are discussed in relation to recent initiatives introduced in the UK where, in the absence of specific regulatory drivers for control, reductions in P loss must rely on voluntary actions taken collectively within the watershed. Integrated control strategies could be implemented, often at relatively low cost and/or with financial advantage to the farmer. Practical management tools are required to help stakeholders identify the key problem areas and avoid them through more precise nutrient and land management. Nutrient management remains a key issue since controls over manure P inputs, and the way they are handled, will have the greatest socioeconomic impact at a range of scales.
Sorption of Prochloraz on Primary Soil Organomineral Size Separates
Authors: de Jonge L. W. , de Jonge H. , Moldrup P. , Jacobsen O. H. , Christensen B. T.
Published: July 2010

The adsorption and desorption of the fungicide prochloraz (N‐propyl‐N‐[2‐(2,4,6‐trichlorophenoxy)‐ethyl]‐1‐H‐imidazol‐1‐carboxamid) to two whole soils and their sand, silt, and day‐size separates were investigated in batch experiments. The size separates were isolated using ultrasonic dispersion in water and repeated gravity sedimentation. For both soils, clay (<2 µm) and silt (2–20 µm) sorbed more prochloraz per kg of soil than did sand (20–2000 µm) and whole soil. Based on unit mass of organic matter, however, whole soils and size separates were equally effective adsorbers. On a unit surface area (BET N2) basis, the silt‐ and sand‐size separates were the most efficient sorbents. Adsorption and desorption isotherms, obtained after 1 and 24 h equilibration, were best described by the Freundlich model. Sorption‐desorption nonsingularity was observed for all size separates, and in general the degree of nonsingularity increased with contact time. Several sorption parameters were well correlated to soil organic C content and to particle porosity, the latter likely representing the pore volume available for diffusion of pesticide toward sorption sites. Adsorption kinetics and adsorption‐desorption nonsingularity could be well described by a two stage‐two rate model. Adsorption kinetics were characterized by a rapid initial adsorption with most of the pesticide being bound within 10 rain followed by a slow adsorption period. When using pesticide transport models that accounts for particle‐mediated transport, it is important to consider that the potentially mobile clay‐ and silt‐size separates typically have higher adsorption capacity than the average capacity of the whole soil.
Effects of Redox Conditions and Flow Processes on the Mobility of Dissolved Organic Carbon and Nitrogen in a Forest Soil
Authors: Hagedorn F. , Kaiser K. , Feyen H. , Schleppi P.
Published: July 2010

In forest ecosystems, organic solutes play prominent roles in pollutant and nutrient transport. This study, conducted in subalpine forested Humaquepts in Switzerland, investigated the influence of redox conditions and flow processes on dissolved organic carbon (DOC) and dissolved organic nitrogen (DON). In the mineral soil, concentrations of DOC were higher under reduced than under oxidized conditions. They averaged 1.2 mmol DOC L−1 in the reduced mineral soil at a 100‐cm depth. A close correlation between DOC and dissolved Fe concentrations (r2 = 0.83; p < 0.001) suggests that reductive dissolution of Fe‐oxides was the major reason for the low retention. However, during aerobic sampling of soil solution from the reduced mineral soil, DOC coprecipitated with Fe. This suggests that the DOC input from reduced mineral soils to aerobic stream water is lower than expected from the high DOC concentrations in the soil. Organic N was the major form of total dissolved N at all soil depths. In the reduced subsoil, dissolved N was completely organically bound. This was probably due to both an immobilization of inorganic N and a low retention of DON. During storms, DOC concentrations increased rapidly with increasing discharge in the subsurface flow. At peak flow, DOC concentrations were doubled, compared with base flow. The molar UV absorptivity of DOC in the subsurface flow corresponded closely to that of the topsoil. These findings suggest that DOC concentrations and properties are sensitive to flow velocities, and that DOC is preferentially transported to the subsoil at high discharge.
Plant‐Bacterial Combinations to Phytoremediate Soil Contaminated with High Concentrations of 2,4,6‐Trinitrotoluene
Authors: Siciliano Steven D. , Greer Charles W.
Published: July 2010

The explosive 2,4,6‐trinitrotoluene (TNT) is a contaminant of concern at abandoned manufacturing and military sites because of its mobility and toxicity. Phytoremediation may play a role in natural attenuation scenarios by reducing TNT levels at point sources. The purpose of this study was to develop a phytoremediation system suitable for use in soils contaminated with high TNT levels. Sixteen grasses were screened for their tolerance to 41 g TNT kg−1 soil. Meadow bromegrass (Bromus erectus Huds.), perennial ryegrass (Lolium perenne L.) and sweet vernalgrass (Anthoxanthum odoratum L.) grew in this soil. Inoculating these grasses with Pseudomonas sp. Strain 14, capable of transforming TNT into mono‐ and di‐amino metabolites, increased the growth of meadow bromegrass but was lethal to perennial ryegrass and sweet vernalgrass. Meadow bromegrass inoculated with Strain 14 reduced TNT levels by 30% compared with the control soil and had 50% more plant biomass than noninoculated plants. Meadow bromegrass, combined with Strain I4, increased the percentage of the culturable soil heterotrophic population containing the genes involved in 2‐nitrotoluene (ntdAa) metabolism 3‐fold, as well as the population containing the genes involved in 4‐nitrotoluene (ntnM) metabolism 14‐fold. Strain I4 inoculation of meadow bromegrass altered the portion of the rhizosphere community involved in nitroaromatic metabolism and led to a reduction in soil TNT levels.
Managing Nitrogen for Water Quality—Lessons from Management Systems Evaluation Area
Authors: Power J. F. , Wiese Richard , Flowerday Dale
Published: July 2010

The Management Systems Evaluation Area (MSEA) project was initiated in 1990 to evaluate existing and develop new N management technologies to reduce the potential adverse impacts of agricultural practices on surface and ground water quality. Field research sites were established in nine Midwestern states. Results from MSEA research showed that nitrate leaching was greatly reduced by changing from furrow to sprinkler irrigation. At least 95% of the nitrate N percolating through tiled soils was intercepted and discharged into surface waters. Computer models indicated that routing tile discharge through wetlands would greatly reduce the nitrate load. Nitrate losses also were reduced by establishing controlled water tables using drainage lines for subirrigation. Preplant and presidedress soil nitrate tests were effective in determining proper N fertilizer rates and reducing nitrate losses. Banding ammoniated fertilizers slowed nitrification rates and nitrate leaching, especially if soil over the bands was packed. A major new technology was proof that crop greenness can be used to monitor crop N sufficiency, and that N deficiencies after the V8 stage can be corrected by sidedressing or fertigation (reactive N management). Inexpensive sensors or aerial photographs can be used to assess crop greenness. Using Global Positioning Systems (GPS), N‐deficient areas of the field can be managed differently from the remainder of the field. These results point to the need to develop site‐specific or precision farming systems to control nitrate losses to water resources and reduce the impact of natural variability in both soils and weather.
Nitrapyrin Behavior in Soils and Environmental Considerations
Authors: Wolt Jeffrey D.
Published: July 2010

Using nitrification inhibitors is a well‐established fertilizer best management practice affording improved fertilizer use efficiency in crop production that may benefit profitability, crop quality, and the environment. The environmental benefit of nitrification inhibitor use in terms of managing N mobility in agroecosystems must be balanced against any environmental costs associated with the practice itself. Nitrapyrin exhibits multiple routes of degradation in the environment (hydrolysis, aerobic and anaerobic metabolism), which along with sorption and volatilization restrict its ability to mobilize to ground or surface water. Management practices (timing, rate, and method of application) that maximize nitrapyrin efficacy, additionally, favor the ultimate fate of nitrapyrin to occur by the linked processes of sorption and degradation within the upper soil profile. Thus, when nitrapyrin is used as a best management practice conducive of optimal fertilizer use efficiency, its environmental fate and behavior attributes minimize potential environmental exposure.
Nutrient Removal by Grasses Irrigated with Wastewater and Nitrogen Balance for Reed Canarygrass
Authors: Geber Ulrika
Published: July 2010

To develop complementary wastewater treatment systems that increase nutrient reduction and recycling, an experiment was conducted to evaluate the efficiency of three grass species as catch crops for N, P, and K at Surahammar wastewater treatment plant (WWTP) in the southern part of Sweden. Another objective was also to assess soil accumulation of N, P, and K and the risk of N leaching by drainage. Three grasses—reed canarygrass (Phalaris arundinacea L.), meadow foxtail (Alopecurus pratensis L.), and smooth bromegrass (Bromus inermis Leyss.)—were irrigated with a mixture of treated effluent and supernatant at two levels of intensity [optimum level (equal to evapotranspiration) and over‐optimal level] and at two nutrient levels, approximately 150 and 300 kg N ha−1. There were small differences in dry matter (DM) yield between grass species and no difference in N removal among species. The amount of N removed in harvested biomass to N applied was 0.58 in 1995 and 0.63 in 1996. The amount of N removed increased with increased nutrient load. Applied amounts of P were the same as P in harvested biomass. All species removed K amounts several times greater than applied amounts. Increased nutrient load increased overall K removal. The low amount of mineral N and especially NO−3‐N in the soil profile in autumn samplings indicate the risk for leaching is small. Soil water NO−3 contents were also low, <2.5 mg NO−3‐N L−1 during the growing season, with a mean value of <1 mg NO−3‐N L−1.
Application of Composted Pulp and Paper Mill Sludge to a Young Pine Plantation
Authors: Jackson M. J. , Line M. A. , Wilson S. , Hetherington S. J.
Published: July 2010

Disposing of sludge recovered from the effluent stream of pulp and paper mills has traditionally involved landfilling. Shortages in landfill space and increasingly stringent environmental regulations in many countries have forced the industry to seek alternative disposal options. We assessed the feasibility of compost‐recycling a primary pulp and paper mill sludge (PMS) for use as a nutrient‐releasing mulch in plantation forestry. The effects of the composted PMS on the growth, nutrition, water relations, and weed suppression in a 3‐yr‐old plantation of radiata pine (Pinus radiata D.Don) on an infertile sandy soil in southern Tasmania were assessed. Compost was applied to the surface without incorporation in 0.5‐m wide bands in tree rows at rates of 0, 20, 40, and 60 metric t ha−1 (dry matter). One year after application of compost, the percentage increase in stem diameter was 40 to 66% greater than that achieved in untreated plots, with better growth at the highest compost application rate. Improved growth of radiata pine after application of compost was primarily attributable to a 17 to 37% increase in the concentration of foliar N and to decreased water stress in amended plots. Nitrogen released from the compost was mostly absorbed by plant roots within the first 20 cm of the soil profile, with no significant movement beyond this depth range. Application of compost prepared from PMS to young stands of radiata pine was found to be an acceptable recycling alternative for this material, capable of improving plantation productivity.
Comparison of Methods for Evaluating Stability and Maturity of Biosolids Compost
Authors: Wu L. , Ma L. Q. , Martinez G. A.
Published: July 2010

Compost stability/maturity has become a critical issue for land application of compost because immature compost can be detrimental to plant growth and the soil environment. We compared several methods of evaluating the stability/maturity of biosolids compost: chemical properties, microbial respiration activity (CO2 evolution), seed germination tests, and dissolved organic carbon (DOC) as determined by its concentration and mass‐specific absorbence (MSA) at 420 nm. Two to five biosolids compost samples were collected during compost curing stages from three full‐scale composting facilities in Florida. The compost samples from two facilities were in the stabilization/maturation process. With curing time, electrical conductivity (EC), DOC concentration, and CO2 evolution rate decreased, whereas pH, seed germination rate, and the MSA of DOC increased in these samples. Compost samples from the third facility exhibited distinctly different behavior. Relatively high seed phytotoxicity, with no consistent trends of other parameters, suggested that these samples may have not been in a real curing process, despite the generally low CO2 evolution rate and DOC content. Based on these results, we concluded that pH, EC, CO2 evolution rate, seed germination rate, and DOC (concentration and MSA) could be used to monitor stabilization and maturation processes. Compost stability and maturity are different characteristics and both are needed for compost quality control. Dissolved organic carbon analysis is promising as a simple but comprehensive index for compost stability/maturity.
Zinc Uptake by Young Wheat Plants under Two Transpiration Regimes
Authors: Grifferty A. , Barrington S.
Published: July 2010

Treated wastewater for crop irrigation is an alternative for countries with a shortage of fresh water. Such practice requires strict wastewater application criteria and a better understanding of the effects of transpiration rate on plant heavy metal uptake. The experiment measured Zn uptake by young wheat plants (Triticum aestivum L.) grown in triplicated experimental pots and held in two growth chambers with constant environmental conditions (relative humidity, light and temperature) but with a different air water vapor pressure deficit to produce two different transpiration rates. After 5 wk of growth in a greenhouse, the plants were transferred to the controlled chambers and irrigated using a fertilized solution with five different levels of Zn: 0, 2, 10, 25, and 50 mg/L. These Zn levels were low enough to have no significant effect on plant growth and transpiration rate. The wheat plants started to produce their grain at 6 wk. Plants were collected at 0, 3, and 10 d of incubation in the controlled chambers and analysed for dry matter and total Zn content. The pots were weighed daily to measure their transpiration rates. On Day 10, the remaining plants were collected and their roots, shoots, and grain were separated, weighed, dried, and analysed for total Zn. Time and plant transpiration rate were found to affect significantly plant Zn uptake. The higher transpiration rate enhanced plant Zn uptake. The roots had the highest Zn uptake followed by the shoots and then the grain.
Lysimeter Study of Nitrate Leaching from a Corn‐Soybean Rotation
Authors: Owens L. B. , Malone R. W. , Shipitalo M. J. , Edwards W. M. , Bonta J. V.
Published: July 2010

High rates of N fertilizer in the production of continuous corn (Zea mays L.) have resulted in excessive nitrate N (NO3‐N) leaching, with concentrations in ground water frequently exceeding the maximum contaminant level (MCL) of 10 mg/L. This study was conducted to determine whether NO3‐N leaching would be reduced by allowing for a legume N credit for soybean [Glycine max (L.) Merr.], and applying less N fertilizer to corn in a corn‐soybean rotation than would be applied to continuous corn. A rye (Secale cereale L.) winter cover crop was used following soybean. In the spring of each corn year, 140 kg N/ha as NH4NO3 was surface applied to two large, undisturbed monolith lysimeters (8.1 m2 surface area, 2.4 m deep), and 196 kg N/ha was applied to two other lysimeters. Prior to 6 yr of this treatment, there was a 6 yr period during which lysimeters received 224 kg N/ha in the spring of the corn year. The highest NO3‐N concentrations and the most transport occurred during the winter/spring soil moisture recharge period (November through April). Concentrations of NO3‐N in the percolate from all four lysimeters were similar, with a 6‐yr, flow‐weighted average of 9.9 ± 2.5 mg/L. Although reducing N fertilizer inputs in a corn‐soybean rotation to allow for a legume N credit may lower N leaching amounts and concentrations, the NO3‐N MCL may still be exceeded. For a given year, weather can impact percolation and leaching more than the current crop.
Chlorofluorocarbon Dating of Herbicide‐Containing Well Waters in Fresno and Tulare Counties, California
Authors: Spurlock F. , Burow K. , Dubrovsky N.
Published: July 2010

Simazine, diuron, and bromacil are the most frequently detected currently registered pesticides in California groundwater. These herbicides have been used for several decades in Fresno and Tulare counties, California; however, previous data are inadequate to determine whether the detections are a result of recent or historical applications (i.e., within the last decade, or 20–30 yr ago). Chlorofluorocarbon (CFC) groundwater age‐dating was used in conjunction with one‐dimensional transport modeling to address this question. The estimated times between herbicide application and subsequent detection in groundwater samples from 18 domestic wells ranged from 3 to 33 yr; the aggregate data indicate that more than half of the detections are associated with applications in the last decade. The data also suggest that changes in groundwater quality arising from modified management practices will probably not be discernible for at least a decade. A secondary objective of this study was to evaluate the contribution of simazine degradates deethylsimazine (DES; 2‐amino‐4‐chloro‐6‐ethylamino‐s‐triazine) and diaminochlorotriazine (DACT; 2,4‐diamino‐6‐chloro‐s‐triazine) to total triazine concentrations (defined here as simazine + DES + DACT) in 30 domestic wells. The N‐dealkylated‐s‐chlorotriazine degradates DES and DACT substantially contribute to total triazine concentrations in Fresno and Tulare County groundwater, composing 24 to 100% of the total triazines, with a median of 82%. If s‐chlorotriazines display a common mode of toxicological action, the prevalence of triazine degradates in water samples found in this and other studies indicate that drinking water standards based on total s‐chlorotriazine concentrations may be most appropriate.
Laboratory Procedures for Characterizing Manure Phosphorus
Authors: Dou Z. , Toth J. D. , Galligan D. T. , Ramberg C. F. , Ferguson J. D.
Published: July 2010

Phosphorus runoff from agricultural land contributes to accelerated eutrophication of surface waters. In areas with intensive animal farming, P loss from manured fields may be elevated due to high concentrations of soluble P in manure. We characterized P in dairy and poultry manure for the relative dissolution and fraction distribution using deionized water (H2O), 0.5 M NaHCO3, 0.1 M NaOH, 1.0 M HCl, and 5% trichloroacetic acid (TCA). Two extraction procedures were tested: (i) independent, with dried, ground samples being extracted repeatedly and P measured for each extractant; and (ii) sequential, with each sample being repeatedly extracted by H2O, NaHCO3, NaOH, and HCl, in that order. For the independent procedure, H2O extracted 53 to 64%, NaHCO3 64 to 72%, NaOH 33 to 54%, HCl 90 to 97%, and TCA 84 to 96% of the total P in manure. Sequentially, H2O, NaHCO3, NaOH, and HCl extracted 70, 14, 6, and 5% of the total P in the dairy, and 49, 19, 5, and 25% of the total P in the poultry sample, respectively. Manure P release was not greatly affected by shaking time but decreased rapidly with increasing number of repeated extractions. A large portion of P in manure being extractable by H2O or NaHCO3 suggests weak binding energy of P and hence a high susceptibility for loss to waters when conditions favor runoff. A 1‐h shaking of manure with H2O may provide a quick measure of the relative magnitude of P that is most susceptible. Further investigation relating manure P fractions with P in runoff would help identify management alternatives for reduced P losses.
Phosphate Losses through Field Drains in a Heavy Cultivated Soil
Authors: Addiscott T. M. , Brockie D. , Catt J. A. , Christian D. G. , Harris G. L. , Howse K. R. , Mirza N. A. , Pepper T. J.
Published: July 2010

Losses of total and molybdate‐reactive phosphate (MRP) were measured for 4 yr in water flowing from interconnecting mole and pipe drains under 0.24 ha plots of a heavy cracking clay soil. The molybdate‐unreactive phosphate (MUP) obtained by difference appeared from the results to be mainly phosphate carried on suspended soil material. The losses of all three categories of phosphate were closely related to the cumulative drainflow, with the same relations covering three of the four years, designated the synoptic years. Losses were much greater in the other year, probably because phosphate was applied after, rather than before, plowing and to very wet soil. The ceiling to annual total phosphate loss, assuming 500 mm drainage, was 0.4 kg ha−1 in the synoptic years, with 76% of the loss occurring as MUP. It was about 1 kg ha−1 in the high‐loss year, with 88% as MUP, implying that MUP comprised 96% of the extra loss that year. Halving the phosphate application lessened the loss of total phosphate but not conclusively, and the decrease in MRP loss was not significant. Restricting and thereby delaying drainage lessened losses of MUP, probably because suspended material carrying it was allowed to settle. Increasing the spacing between mole channels from 2 m to 4 m increased the losses of MUP but not MRP. This probably happened because to meet a flow pathway connected to a mole channel, rainwater had to travel further horizontally and collected more phosphate‐containing soil material.
Historical Sediment Flux from Three Watersheds into Lake Pepin, Minnesota, USA
Authors: Kelley D. W. , Nater E. A.
Published: July 2010

This contribution presents an assessment of the modern and historic fluxes of sediments exiting the Mississippi, St. Croix, and Minnesota watersheds and entering Lake Pepin, a natural riverine lake on the Upper Mississippi River. A Chemical Mass Balance receptor model and elemental signatures for sediments in Lake Pepin and the rivers draining its three principal catchment areas were used to apportion sediments in the lake to their source watersheds. The apportionment data, estimated trapping efficiency of the lake, and watershed basin areas were used to calculate sediment fluxes and erosion rates for each basin on a decadal basis. The relative apportionment of sediments from the Minnesota River watershed increased since European settlement of the region circa 1830 from 83 to 87% for the upper, 83 to 90% for the middle, and 78 to 87% for the lower reaches of the lake. Sediment loading to the whole lake shows a 12‐fold increase from historic levels in the mass of Minnesota River‐derived sediments. The amount of sediment currently supplied by this river is more than seven times the amount supplied by the headwater‐Mississippi and St. Croix Rivers combined. Sediment contributions from these two combined watersheds have risen sevenfold since settlement. The causes of these increases are attributable to intensive agricultural production, especially within the Minnesota River basin. Watershed alterations have resulted in a decrease in wetlands, riparian zones, and native prairie and an increase in acreage artificially drained by sub‐surface tile lines and surface ditching.
Quantity and Quality of Autumnal Litterfall into a Rehabilitated Agricultural Stream
Authors: Oelbermann Maren , Gordon Andrew M.
Published: July 2010

Litterfall from riparian vegetation is a major source of nutrients for stream invertebrates. However, replacement of riparian forests with agricultural crops may result in reduced litter quantity and quality and therefore severely affect stream trophic structure. Litterfall inputs and their associated N flux were measured in 1996 and 1997 at Washington Creek, an agriculturally degraded stream in southern Ontario, Canada. Litterfall varied significantly (p < 0.05) among three treatment areas, with varying tree densities (3.14, 2.43, and 2.17 trees m−2, respectively) and land use. Litterfall was highest (1611 kg ha−1 yr−1) in sections with a wide buffer zone, although it was significantly less (p < 0.05) compared with litterfall in a mature riparian zone (= control, 3238 kg ha−1 yr−1). Leaves represented similar proportions of total litterfall at both the rehabilitated (91.7%) and control (98.2%) site. Litterfall varied significantly (p < 0.05) among trap orientation for both 1996 and 1997 litter collections and was highest in traps oriented south‐west (the predominating wind direction) and perpendicular to the stream. Total N flux varied significantly (p < 0.05) among treatment areas of the rehabilitated site and the mature riparian zone. A higher N flux was found in treatment areas with a wide buffer zone directly adjacent to intensely cropped agricultural fields. This suggests that trees in the riparian zone may be intercepting agricultural runoff and enhancing water quality by converting NO−3‐N runoff to organic forms of N in canopy components. A leaf litter C:N ratio of 32:1 at the rehabilitated site suggests that N may be readily available for stream invertebrates and higher trophic levels.
Soil Carbon Dynamics beneath Switchgrass as Indicated by Stable Isotope Analysis
Authors: Garten C. T. , Wullschleger S. D.
Published: July 2010

Surface (0–40 cm) soil organic carbon (SOC) dynamics were studied beneath four switchgrass (Panicum virgatum L.) field trials in the southeastern United States. Soil organic carbon was partitioned into particulate organic matter (POM) and mineral‐associated organic matter (MOM). Most (75–90%) of the SOC at each study site was affiliated with MOM (<0.053 mm). Changes in stable carbon isotope ratios were used to derive carbon inputs to and losses from POM and MOM at each site. Inventories of existing SOC and new C4‐derived SOC beneath switchgrass decreased with increasing soil depth. Approximately 5 yr after establishment, 19 to 31% of the existing SOC inventories beneath switchgrass had been derived from new C4‐carbon inputs. Calculated turnover times of POM and MOM ranged from 2.4 to 4.3 yr and 26 to 40 yr, respectively. The turnover time of SOC in the POM fraction increased with decreasing mean annual temperature. A simple, two‐compartment model was parameterized to predict the potential for soil carbon sequestration under switchgrass. An example calculation with the model indicated a measurable and verifiable recovery of soil carbon (≈12% increase) on degraded lands through one decade of switchgrass production. The potential to sequester carbon through switchgrass cultivation will depend on initial soil carbon inventories, prevailing climate, soil type, and site management.
A Conceptual Model and Indicators for Assessing the Ecological Condition of Agricultural Lands
Authors: Hess George R. , Campbell C. Lee , Fiscus Daniel A. , Hellkamp Anne S. , McQuaid Betty F. , Munster Michael J. , Peck Steven L. , Shafer Steven R.
Published: July 2010

As part of an environmental monitoring and assessment effort, we developed a conceptual model for measuring and assessing the condition and sustainability of agroecosystems. An agroecosystem is a field, pasture, or orchard and the associated border areas. We focused on ecological sustainability and defined the goals for agroecosystems in terms of the values people place on them. The purpose of an agroecosystem is to produce food and fiber. Other desired outcomes can be considered as goals for the larger landscape and the rest of the world, and they sometimes function as constraints on production. Condition is defined by agroecosystem productivity and the degree to which farmers use management and stewardship practices that conserve and protect valued natural resources in the landscape and the rest of the world. An agroecosystem in good condition is productive and is managed to conserve valued resources. Sustainability is the maintenance of good condition over time. We developed indicators that link system condition and sustainability to societal values and goals. These indicators measure productivity, management practices that promote sustainability at the agroecosystem scale, and management practices that promote sustainability at landscape and global scales. Our initial efforts focused on annually harvested herbaceous crops; however, the concepts we used can be adapted to other plant and livestock systems. Our conceptual approach may be used to evaluate the effectiveness of several major programs now being implemented, including the USDA's Environmental Quality Incentive and Conservation Reserve Programs.
Greenhouse Gas Emission from Stored Livestock Slurry
Authors: Sommer Sven G. , Petersen Søren O. , Søgaard Henning T.
Published: July 2010

Animal manure contributes about 40% of the total methane (CH4) and 20% of the total nitrous oxide (N2O) emissions in Denmark. We measured the CH4 and N2O emissions from stored cattle slurry and fermented slurry during fall 1996 and summer 1997 and evaluated the effect of surface covers consisting of straw, floating leca pebbles, or a natural surface crust on the patterns of these emissions. No emission of N2O was measured during periods with more rain than evaporation from the slurry stores and no emission was measured from uncovered slurry, irrespective of climatic conditions. During the summer storage with drying conditions, N2O emissions of up to 25 mg N m−2 h−1 were recorded from slurry with surface covers. Total N2O emission was highest from digested slurry. The emission of CH4 from stored fermented slurry and cattle slurry varied between <0.01 and 1.4 or 0.7 g CH4—C m−3 h−1, respectively. The log‐transformed emissions were linearly related to the inverse temperature. Emission of CH4 was reduced, on average, by 38% with surface covers. The reduction was probably due to CH4 oxidation in the surface covers or in the interface between the cover and liquid in the store. Fermentation did not reduce CH4 emissions during storage of the slurry.