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Reactive P (reactive + p)

Distribution by Scientific Domains

Earth and Environmental Science	100%

Selected Abstracts

Lime and cow slurry application temporarily increases organic phosphorus mobility in an acid soil

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2007
P. 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]

Enhancing the P trapping of pasture filter strips: successes and pitfalls in the use of water supply residue and polyacrylamide

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2008
M. R. Redding
Summary In intensive pastoral systems the landscape at ground level is clad in dense, filtering vegetation , yet phosphorus losses in overland flow do occur, and pollution of surface waters is a serious consequence. The use of pre-applied polyacrylamide (PAM) or chitosan to trap particulate phosphorus (PP) and P-sorbing potable water treatment alum residue (PWTR) to enhance vegetative filtering effects is examined here using field and laboratory overland flow simulation (flows from 0.43 to 0.34 litres s,1 (m width),1) and analysis. Fitted equations suggest that up to 40% of dissolved reactive P applied (0.75 mg P litre,1) in overland flow could be captured in a flow length of 2.1 m (1 kg PWTR m,2). Unfortunately, drying decreased PWTR effectiveness, though little of the P captured was readily desorbed. This effect did not appear to be the result of gibbsite formation. Compared with the other treatments, there was a strong treatment effect of pre-applied PAM on the change in PP losses (P < 0.001) over time, though evidence suggests the PAM effect declined during a 44 minute flow period. We showed that the investigated two-pronged approach to the enhancement of the effectiveness of P trapping by pasture had limitations. Laboratory sheet-flow simulations suggest that a field-stable P sorber with sorption characteristics similar to those of the un-dried PWTR could be an effective retention enhancer for dissolved P. Pre-applied PAM can have an effect on particulate-P trapping but was rapidly dissolved and removed by flow. [source]

Preferential phosphorus leaching from an irrigated grassland soil

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 2 2005
G. S. Toor
Summary Intact lysimeters (50 cm diameter, 70 cm deep) of silt loam soil under permanent grassland were used to investigate preferential transport of phosphorus (P) by leaching immediately after application of dairy effluent. Four treatments that received mineral P fertilizer alone (superphosphate at 45 kg P ha,1 year,1) or in combination with effluent (at , 40,80 kg P ha,1 year,1) over 2 years were monitored. Losses of total P from the combined P fertilizer and effluent treatments were 1.6,2.3 kg ha,1 (60% of overall loss) during eight drainage events following effluent application. The rest of the P lost (40% of overall loss) occurred during 43 drainage events following a significant rainfall or irrigation compared with 0.30 kg ha,1 from mineral P fertilizer alone. Reactive forms of P (mainly dissolved reactive P: 38,76%) were the dominant fractions in effluent compared with unreactive P forms (mainly particulate unreactive P: 15,56%). In contrast, in leachate following effluent application, particulate unreactive P was the major fraction (71,79%) compared with dissolved reactive P (1,7%). The results were corroborated by 31P nuclear magnetic resonance analysis, which showed that inorganic orthophosphate was the predominant P fraction present in the effluent (86%), while orthophosphate monoesters and diesters together comprised up to 88% of P in leachate. This shows that unreactive P forms were selectively transported through soil because of their greater mobility as monoesters (labile monoester P and inositol hexakisphosphate) and diesters. The short-term strategies for reducing loss of P after application of dairy effluent application should involve increasing the residence time of applied effluent in the soil profile. This can be achieved by applying effluent frequently in small amounts. [source]

Effect of land use on some soil properties related to the risk of loss of soil phosphorus

LAND DEGRADATION AND DEVELOPMENT, Issue 1 2008
F. Troitiño
Abstract Although land use clearly modifies soil properties, the intensity of the modifications depends on the management procedures and also on the soil properties themselves. To enable construction of models that describe soil nutrient losses, extensive databases corresponding to soils under different land use must be made available. Analysis of 404 samples of soils (from Galicia, NW Spain), under different types of use revealed that most of the soil properties underwent changes in the following order: forest use (least modified) - grassland - arable (most modified). Decreases in the contents of organic matter, extractable oxides and P-adsorption capacity followed the same order, as did increases in the contents of available P (total, inorganic and organic), P desorbed with distilled water, and degree of P saturation. In general, in all of the soils, independently of their use, the amount of P desorbed (whether total P, molybdate reactive P or particulate P) was more closely related to the degree of P saturation than to the levels of P extracted with bicarbonate. Copyright © 2007 John Wiley & Sons, Ltd. [source]