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P Loss (p + loss)
Selected AbstractsLime and cow slurry application temporarily increases organic phosphorus mobility in an acid soilEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2007P. N. C. MurphyArticle first published online: 13 OCT 200 Summary Phosphorus loss from agricultural soils to water is recognized as a major contributor to eutrophication of surface water bodies. There is much evidence to suggest that liming, a common agricultural practice, may decrease the risk of P loss by decreasing P solubility. An unsaturated leaching column experiment, with treatments of control and two lime rates, was carried out to investigate the effects of liming on P mobility in a low-P acid Irish soil, which was sieved and then packed in columns. Phosphorus was applied at the soil surface in the form of KH2PO4 in solution or as cow slurry. Soil solution was sampled at time intervals over depth and analysed for P fractions. Organic P (OP) was the dominant form of P mobile in soil solution. Liming increased OP mobility, probably through increased dispersion of OP with increased pH. Slurry application also increased OP mobility. Results indicated the potential for OP loss following heavy (100 m,3 ha,1) cow slurry application, even from low-P soils, and suggested that liming may increase this risk. Reactive P (RP) was sorbed strongly and rapidly by the soil and did not move substantially below 5 cm depth. As a result, Olsen-P values in the top 2 cm were greatly increased, which indicates an increased risk of RP loss in overland flow. Lime showed little potential as a soil amendment to reduce the risk of P loss. [source] Estimation of the phosphorus sorption capacity of acidic soils in IrelandEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2001R. O. Maguire Summary The test for the degree of phosphorus (P) saturation (DPS) of soils is used in northwest Europe to estimate the potential of P loss from soil to water. It expresses the historic sorption of P by soil as a percentage of the soil's P sorption capacity (PSC), which is taken to be , (Alox + Feox), where Alox and Feox are the amounts of aluminium and iron extracted by a single extraction of oxalate. All quantities are measured as mmol kg soil,1, and a value of 0.5 is commonly used for the scaling factor , in this equation. Historic or previously sorbed P is taken to be the quantity of P extracted by oxalate (Pox) so that DPS = Pox/PSC. The relation between PSC and Alox, Feox and Pox was determined for 37 soil samples from Northern Ireland with relatively large clay and organic matter contents. Sorption of P, measured over 252 days, was strongly correlated with the amounts of Alox and Feox extracted, but there was also a negative correlation with Pox. When PSC was calculated as the sum of the measured sorption after 252 days and Pox, the multiple regression of PSC on Alox and Feox gave the equation PSC = 36.6 + 0.61 Alox+,0.31 Feox with a coefficient of determination (R2) of 0.92. The regression intercept of 36.6 was significantly greater than zero. The 95% confidence limits for the regression coefficients of Alox and Feox did not overlap, indicating a significantly larger regression coefficient of P sorption on Alox than on Feox. When loss on ignition was employed as an additional variable in the multiple regression of PSC on Alox and Feox, it was positively correlated with PSC. Although the regression coefficient for loss on ignition was statistically significant (P <,0.001), the impact of this variable was small as its inclusion in the multiple regression increased R2 by only 0.028. Values of P sorption measured over 252 days were on average 2.75 (range 2.0,3.8) times greater than an overnight index of P sorption. Measures of DPS were less well correlated with water-soluble P than either the Olsen or Morgan tests for P in soil. [source] Among- and within-species variation in plant litter decomposition in contrasting long-term chronosequencesFUNCTIONAL ECOLOGY, Issue 2 2009David A. Wardle Summary 1Following major disturbances ecosystem development occurs but in the prolonged absence of disturbance a decline (retrogressive) phase follows in which productivity and nutrient availability diminishes. Although it is recognized that litter quality and decomposition rates decrease as retrogression proceeds, little is known about the extent to which this is driven among- vs. within-species variation across these sequences. 2We selected six long-term chronosequences that each included retrogressive stages, in New Zealand, Hawaii, Sweden, Alaska and Australia. Two involve significant species turnover across the sequence so that different species dominate at different stages, two involve low species turnover so that the same dominant species occur at all stages, and two involve some turnover of species but with certain species persisting throughout most of the sequence. 3For each chronosequence, we collected litter from each dominant plant species at each stage of that sequence. For each litter collection we measured concentrations of N and P, and performed laboratory decomposition bioassays to measure mass loss, N and P loss, and the response of mass loss to mixture with litters of coexisting species. 4We found that litter N and P concentrations often declined with increasing ecosystem age, both among- and within-species. However, the relative importance of among- and within-species effects varied across the six chronosequences. Rates of litter mass, N, and P loss during decomposition sometimes decreased with increasing ecosystem age, but most often at the among-species rather than the within-species level. 5Litter mixing effects often varied across chronosequence stages, but the magnitude and direction of these effects was inconsistent among sequences. Variation in litter mixing effects across chronosequence stages was driven mainly by among- rather than within-species variation. 6Although several recent studies have emphasized the role of within-species variation on ecosystem properties, our results point to among-species variation as a consistently important ecological driver, with within-species variation being important only for some variables and in some instances. As such they highlight that decomposition processes are most likely to be highly responsive to gradients of soil fertility (such as across chronosequences) when significant species turnover occurs across the gradient. [source] Risk assessment methodologies for predicting phosphorus losses,JOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 4 2003Oscar F. Schoumans Abstract Risk assessment parameters are needed to assess the contribution of phosphorus (P) losses from soil to surface water, and the effectiveness of nutrient and land management strategies for the reduction of P loss. These parameters need to take into account the large temporal and spatial variation in P transfer from individual fields arising from (a) changing but predictable factors such as land use, soil P status, P application rates, forms and ways of fertilization and spreading, (b) predictable but inherent factors such as soil type, soil dispersivity, slope and hydrological routing, and (c) unpredictable weather factors such as rainfall amount and intensity. In most situations, water transport is the driving force of P loss from agricultural land to surface water. Therefore, the hydrological pathways determine to a large extent the relevance of these different factors. Over the last decade several soil P tests have been proposed as a first step to link field conditions to risk of P loss. The major reason is that these soil P tests are also meaningful in discussions with farmers. Recently, more complex P loss risk parameters have been derived based on different approaches. However, the scope and purposes of these P loss risk parameters vary remarkably. Finally, there is a need to evaluate the usefulness of new P tests that can be used as an indicator of P loss risk, e.g. in relation to monitoring purposes. The implementation of the EU Water Framework Directive will increase this need. In this paper, the practicable applicability of P parameters for risk assessment is discussed in relation to purpose, scale (from field, farm to catchment), effectiveness, sensibility etc. Furthermore, a conceptual framework for P indicators is presented and evaluated, based on the outcome of the presentations and the discussions in Zurich. No translation. [source] Nutrient utilisation in response to dietary supplementation of chicory inulin in growing pigsJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 9 2004Todd C Rideout Abstract The digestive and post-absorptive utilisation of dietary crude protein (CP), calcium (Ca) and phosphorus (P) in response to dietary supplementation of chicory inulin extract was investigated with six Yorkshire barrows with an average initial body weight of 30 kg. The barrows were fed a corn (maize) and soybean meal-based diet containing 0 or 50 g kg,1 chicory inulin extract according to a two-period crossover design. The digestive utilisation of CP, Ca and P did not differ (P > 0.05) between the control and the inulin-fed pigs. Furthermore, the post-absorptive urinary loss of CP and Ca was not affected (P > 0.05) by 50 g kg,1 chicory inulin supplementation. However, inulin supplementation improved post-absorptive P utilisation through a reduction (P = 0.01) in urinary P loss by 1.6 percentage units compared with the control group. In conclusion, dietary supplementation of 50 g kg,1 chicory inulin does not affect dietary CP and Ca utilisation but does reduce urinary P loss in growing pigs. Copyright © 2004 Society of Chemical Industry [source] Effect of water composition on phosphorus concentration in runoff and water-soluble phosphate in two grassland soilsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2006M. Schärer Summary Many irrigation experiments determine phosphorus (P) losses from soil. Often, these studies cannot be compared, because the irrigation water was not characterized. We used calcium-rich tap water and deionized water to investigate the influence of water composition on P concentrations in induced runoff. We irrigated two grassland sites: one acid and one calcareous. Less P was measured in runoff from tap water irrigation than from deionized water, especially for the acid soil. Batch experiments confirmed the findings of the field experiments. Tap water decreased water-soluble phosphate and increased calcium in the solid phase. This interaction increased with decreasing soil:water ratio. Water of low ionic strength gave results comparable to rainwater. Our findings demonstrate that solution chemistry and the soil:water ratio can strongly influence the availability of P for transport. We recommend that P tests or irrigation experiments should use water resembling that of the system of interest. Irrigation experiments aiming to simulate P losses by surface runoff should be carried out with water having a composition comparable to rainwater. [source] Spatial variability of sequentially extracted P fractions in a silty loamJOURNAL OF PLANT NUTRITION AND SOIL SCIENCE, Issue 3 2005Elena Heilmann Abstract Knowledge of the spatial distribution of soil P forms in agricultural fields is important for evaluating the risk of P transfer to waterways. The objective of this study was to characterize the spatial variation of total P (Pt) and sequentially extracted P forms in the Ap horizon of arable soils at the field scale. Soil samples were taken on a regular grid of 50 m × 50 m with 40 sampling points. Chemical analyses included basic soil properties, Pt, sequentially extracted P forms, and acid phosphomonoesterase activity. The spatial variability was analyzed by geostatistics and descriptive statistics. The concentrations of Pt ranged from 521 to 1020 mg,kg,1 with lower values observed for Gleysols and Stagnic Phaeozems and higher values for Luvisols and Cambisols. For the sequentially extracted P fractions, the largest coefficients of variation (c.v.) were found for NaHCO3 -Po (41%), NaHCO3 -Pi (36%), NaOH-Po (34%), and resin-P (33%). Despite this great spatial variability, no spatial dependence could be proved by geostatistics because the calculated range of P forms (<10 m) was below the smallest sampling distance (50 m). A clear trend of increasing concentrations and proportions of organic NaHCO3 - and NaOH-P fractions and phosphomonoesterase activity towards lower slope positions and the discharging brook indicated that Gleysols were a particular source of P losses to waterways in this catchment. It was concluded that these soils require a specific management with reduced P inputs and, perhaps, chemical treatment to fix leachable P. Räumliche Variabilität sequenziell extrahierter P-Fraktionen in einem Schlufflehm Kenntnisse über die räumliche Verteilung der P-Formen in landwirtschaftlichen Flächen sind notwendig für die Abschätzung des Risikos von P-Austrägen. Gegenstand dieser Untersuchung war die räumliche Verteilung von Gesamt-P (Pt) und P-Formen im Ap-Horizont von landwirtschaftlich genutzten Böden im Feldmaßstab. Dazu wurden Proben auf einem Raster von 50 m × 50 m an 40 Punkten entnommen. Die chemischen Analysen umfassten Grundeigenschaften sowie Pt, sequenziell extrahierte P-Formen und die Aktivität der sauren Phosphomonoesterase. Die räumliche Variabilität wurde mit räumlicher und deskriptiver Statistik untersucht. Die Pt -Gehalte lagen im Bereich von 521 bis 1020 mg,kg,1, wobei Gleye und Pseudogleye die niedrigsten Werte hatten. Bei den sequenziell extrahierten P-Fraktionen wurden die größten Variationskoeffizienten für NaHCO3 -Po (41%), NaHCO3 -Pi (36 %), NaOH-Po (34 %) und Harz-P (33 %) festgestellt. Trotz dieser großen räumlichen Variabilität konnte mit Geostatistik keine räumliche Abhängigkeit nachgewiesen werden, möglicherweise weil die geschätzte Reichweite der P-Formen mit <10 m unterhalb der kleinsten Beprobungsdistanz von 50 m lag. Deutliche gerichtete Trends steigender Gehalte und Anteile organischer NaHCO3 - und NaOH-P-Fraktionen und Phosphomonoesterase-Aktivitäten hin zu niedrigeren Geländepositionen und zur Nachbarschaft zu dem entwässernden Bach deuteten darauf hin, dass insbesondere Gleye eine Quelle der P-Einträge in Oberflächengewässer des Einzugsgebietes sein können. Es ergibt sich daher die Schlussfolgerung, dass diese Böden einer teilschlagspezifischen Bewirtschaftung mit reduzierten P-Zufuhren und eventuell P-fixierenden Behandlungen bedürfen. [source] Impacts of Alternative Manure Application Rates on Texas Animal Feeding Operations: A Macro Level Analysis,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 3 2008E. Osei Abstract:, An integrated economic and environmental modeling system was developed for evaluating agro-environmental policies and practices implemented on large scales. The modeling system, the Comprehensive Economic and Environmental Optimization Tool-Macro Modeling System (CEEOT-MMS), integrates the Farm-level Economic Model (FEM) and the Agricultural Policy Environmental eXtender (APEX) model, as well as national databases and clustering and aggregation algorithms. Using micro simulations of statistically derived representative farms and subsequent aggregation of farm-level results, a wide range of agricultural best management practices can be investigated within CEEOT-MMS. In the present study, CEEOT-MMS was used to evaluate the economic and water quality impacts of nitrogen (N) and phosphorus (P) based manure application rates when implemented on all animal feeding operations in the State of Texas. Results of the study indicate that edge-of-field total P losses can be reduced by about 0.8 kg/ha/year or 14% when manure applications are calibrated to supply all of the recommended crop P requirements from manure total P sources only, when compared to manure applications at the recommended crop N agronomic rate. Corresponding economic impacts are projected to average a US$4,800 annual cost increase per farm. Results are also presented by ecological subregion, farm type, and farm size categories. [source] | ||||||||||