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During the irrigation period, the interactions between the linked lake-groundwater systems are complicated and change. This is because natural and human activities are happening at the same time, which makes it harder to identify the interactions. This study uses data on water level, hydrochemistry, and hydrogen-oxygen stable isotopes to analyze the hydrodynamics, electrical conductivity (EC), isotopic characteristics, and spatial distribution of lake water and groundwater to reveal lake-groundwater interactions. The results indicate that the hydrochemical type of Chagan Lake and groundwater is dominated by the HCO3-Na type. The key hydrochemical indicator EC obtained by principal component analysis (PCA) can be used to reveal the lake–groundwater interaction, and the interaction should be identified by location according to the significant correlation between hierarchical clustering results and regional distribution. The lake body's geographic coefficient of variation for EC and δ18O is small, and irrigation return flow is one factor in the region's surface water's significant spatial variation for EC and δ18O. The three study methods indicate that the groundwater supplies the lake in the vicinity of the Huoling River-Hongzi Pool, while in other sections, the lake water leaks and replenishes the groundwater, exhibiting geographic inconsistency. The isotope method was employed as a support tool to determine that groundwater might recharge the lake at Xinmiao Pool. According to the calculations of the Mix SIAR model, the groundwater recharge contribution rate in the Xinmiao Pool section is approximately 51%, while in the remaining sections, the contribution rate of lake water to groundwater ranges from approximately 25% to 52%. Therefore, the identification of the interaction is crucial for the linked irrigated lake-groundwater system where water sources are scarce and threatened by agricultural pollution. [ABSTRACT FROM AUTHOR]

Emissions of nitrous oxide (N2O) from aquatic ecosystems are on the rise due to the dramatic increase in global reactive nitrogen input by anthropogenic activities (e.g., agricultural nitrogen fertilizer use). However, uncertainties exist in the estimation of aquatic N2O budgets due to limited knowledge of mechanisms involved in aquatic N2O emissions, as well as the N2O flux measurements and modelling. To give a full picture of aquatic N2O emissions, this review discusses the biotic and abiotic mechanisms involved in aquatic N2O emissions, common methods used in aquatic N2O flux measurements (including field measurement methods and formula simulation methods), and alternatives for aquatic N2O budget estimation. In addition, this review also suggests that stable isotope technology is promising in the application of aquatic N2O source partitioning. [ABSTRACT FROM AUTHOR]

Introduction: Sulfate is one of the important groundwater pollutant sources in many parts of the world and it can enter into groundwater from various sources, such as lithology (dissolution of evaporative and pyrite oxidation), atmosphere (sea water spray), industrial (combustion of fossil fuels, sulfide- minerals production, and agricultural fertilizers), and etc. Identifying sources of soluble sulfate in water sources is important. The sulfate in groundwater can be investigated using isotope and geochemistry techniques. Using isotope (34S and 18O) and hydro geochemical techniques, it can be possible to find out: sulfate origins and the effective processes/reactions on sulfate concentrations and hydrogen sulfide gas (H2S) production. In this paper, for the first time, the sulfate source in groundwater of Sarpol Zahab and the parameters affecting sulfate concentration and its isotopic compositions (d34S and d18O) in groundwater were studied. Sarpol-e Zahab is located in the catchment area of Alvand river in the west of Kermanshah province, west of Iran. The formations of the region, based on age from old to new, include the Ilam, Gurpi, Amiran, Telezang, Pabdeh, Asmari, Gachsaran, Aghajari, Bakhtiari and Quaternary alluvium formations. Asmari formation and Quaternary alluvial sediments form the largest area of the region. Gachsaran formation contains evaporative materials which is reducing the quality of groundwater in the region. Ilam formation is effective in providing the organic matter required for the bacterial sulfate reduction process. Materials and Methods: 13 water samples were taken from the water resources (wells, springs and river) of Sarpol-e Zahab region in two steps (December 2014 and September 2015). Measuring field parameters (T, pH, Eh, Ec, and TDS) and sampling of water resources were performed according to the instructions of Groundwater and Geothermal Research Center (GRC), Ferdowsi University of Mashhad. Field parameters were measured by VWR Handheld Multi parameter Research meter at the location of each water source. The concentration of cations and the anions were determined by the devices inductively coupled plasma elemental analyzer (ICP-EA) and ion chromatography (IC), respectively. Chemical and isotopic analyses of all water samples were performed in Ottawa university geochemistry laboratory and Waterloo university isotope laboratory, respectively. The measurement reference for isotopic sulfate and oxygen were VCDT and VSMOW, respectively, and the value isotopic are expressed as permil ((‰. Results and Discussion: The sulfate concentrations in different water resources of the region varied from 5 to 950 mg L, however, it is very high in Gandab spring’ water, due to the association with hydrocarbons, and in Patagh Tunnel water, due to discharging of water from Gachsaran Formation (339.6 mg L and 950.1mg L, respectively). Chenarpiran spring has the lowest sulfate concentration because it is located in highlands and is discharged from Asmari formation with good water quality. The amount of d18O varied between 5.8 to 13.1 VCDT ‰ and the amount of d34S ranges from 9.5 to 31.8 VSMOW ‰. In Gandab spring’ water, due to sulfate reduction by microorganisms, in addition to the unpleasant smell of sulfide hydrogen (H2S), the d34S and d18O values were enriched than the isotopic composition of other water sources ( about 31.8 ‰ and 10.3 ‰, respectively). In other hand, the Gel va Darreh spring's water, due to the effect of upstream bath waste water (soap and detergent with a value of about 1 ‰ for d34S), indicated depleted isotope values. Conclusion: The concentration and isotopic composition of sulfate in the water resources of the Sarpol-e Zahab region are affected by the geological, atmospheric, human and hydrocarbon materials. The impact of human and hydrocarbon factors on the concentration and isotopes of sulfate is local, however, the lithology effects are on all water resources of the region. Since, Gachsaran formation forms the alluvial aquifer bedrock of Ghaleshahin plain, the dissolution of gypsum has an effective role in the hydro chemical evolution of the alluvial aquifer of this plain. The lithology of the area is often limestone and evaporation. Due to the high solubility of these materials in water, they have been able to have a significant effect on sulfate isotopic in water sources. The amount of measured isotopic values indicated that the origin of evaporators and atmospheric sulfate is in water. The dissolution of the evaporation formation has reduced the water quality. The association of bedrock in the Gandab spring has led to have a reduction environment and the occurrence of sulfate reduction and production of hydrogen sulfide gas (H2S). The human activities (by making bath upstream) caused oxidizing conditions, isotopic depletion and contamination of the Glodarreh spring.

Emissions of nitrous oxide (N2O) from aquatic ecosystems are on the rise due to the dramatic increase in global reactive nitrogen input by anthropogenic activities (e.g., agricultural nitrogen fertilizer use). However, uncertainties exist in the estimation of aquatic N2O budgets due to limited knowledge of mechanisms involved in aquatic N2O emissions, as well as the N2O flux measurements and modelling. To give a full picture of aquatic N2O emissions, this review discusses the biotic and abiotic mechanisms involved in aquatic N2O emissions, common methods used in aquatic N2O flux measurements (including field measurement methods and formula simulation methods), and alternatives for aquatic N2O budget estimation. In addition, this review also suggests that stable isotope technology is promising in the application of aquatic N2O source partitioning.

Copyright of Water & Soil is the property of Ferdowsi University of Mashhad Press and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In Chile, erosion processes (on-site and off-site impact) affect at least 36.9 million ha–1, representing 49% of the total land area. Different regions show severe soil degradation mainly caused by water erosion processes. The importance of sediment-associated transport and the key role of soil erosion affect the fertility of the land and the contamination of water bodies. The aim of this work was to estimate the erosion rate, caused by the rainfall in Apalta vineyards in the Libertador General Bernardo O'Higgins Region of Chile using isotope techniques, assessing the 7Be runoff during four years (2009–2012). The 7Be distribution mass depth at a reference site ranged from 7 to 24 kg m–2 in the first two centimetres soil layer. Even when the vineyards have been well managed, the topographic characteristics and the climatic conditions facilitated soil erosion, with average rates of 50.4, 23.5, 50.6 and 67.3 tons ha–1 y–1 in 2009, 2010, 2011 and 2012, respectively. The robustness of the 7Be technique demonstrated the advantage of a non-soil-destructive methodology to calculate soil distribution and erosion rates. [ABSTRACT FROM AUTHOR]

Minable rock phosphate is a finite resource. Replacing mineral phosphorus (P) fertilizer with P-rich secondary resources is one way to manage P more efficiently, but the importance of physicochemical and microbial soil processes induced by secondary resources for plant P uptake are still poorly understood. Using radioactive labelling techniques, the fertilization effects of dairy manure, fish sludge, meat bone meal and wood ash were studied as P uptake by barley after 44 days and compared with those of water-soluble mineral P (MinP) and an unfertilized control (NoP) in a pot experiment with an agricultural soil containing little available P at two soil pH levels, approximately pH 5.3 (unlimed soil) and pH 6.2 (limed soil). In a parallel incubation experiment, the effects of the secondary resources on physicochemical and microbial soil processes were studied. The results showed that the relative agronomic efficiency compared with MinP decreased in the order: manure ≥ fish sludge ≥ wood ash ≥ meat bone meal. The solubility of inorganic P in secondary resources was the main driver for P uptake by barley (Hordeum vulgare). The effects of secondary resources on physicochemical and microbial soil processes were of little overall importance. Application of organic carbon with manure resulted in microbial P immobilisation and decreased uptake by barley of P derived from the soil. On both soils, P uptake by barley was best explained by a positive linear relationship with the H2O + NaHCO3-soluble inorganic P fraction in fertilizers, or by a linear negative relationship with the HCl-soluble inorganic P fraction in fertilizers.

Authentication of a food product is the procedure by which it is verified that the product matches the statements on the label, and that it conforms to what is established by regulations. This testing process includes analysis of the ingredients, determination of the geographical origin, and examination of the production methods. In particular, the use of rapid, effective and reliable analytical methods, when correctly applied to verify the authenticity and the traceability of the product, represents a valuable and irreplaceable tool for the authorities to carry out control functions. Tools and methodologies from scientific innovation and technological evolution can help to quickly locate particularly sophisticated frauds and adulterations. The feeding regime of livestock is a fundamental issue for the properties and safety of animal origin food, but this regime is often hidden from the consumer, making the zootechnical sector more prone to fraudulent practices. This review reports the results recently obtained in authentication of animal origin food by the application of stable-isotope ratio analysis, the most promising analytical technique in this field.© 2012 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Crop-assimilated carbon (C), an important source of soil organic carbon (SOC), represents a key linked component of the C cycle in the soil-plant-atmosphere continuum. In the farmland ecosystem, however, the quantitative characterization and mechanism involved in the distribution and transformation of the assimilated C in soil over the plant's life cycle are problems relatively easily ignored. Research in this area is therefore indispensable for a thorough understanding of the process and characteristics of the organic C cycle in farmland soil. This paper provides an overview on: (1) the distribution, transformation rules, and structural features of crop-assimilated C in soil and its contribution to SOC and the function of microorganisms in the transformation of assimilated C. (2) The chemical compositions and structural features of the assimilated C after its entry into soil organic matter. (3) The relationship between assimilated C, rhizosphere deposition, and C isotope technology. Based on the findings, we consider that further research on the distribution of crop-assimilated C in the soil-crop system and the quantitative relations of several C-transformation steps such as crop input, transformation, protection, and stabilization in different ecosystems should be conducted. Moreover, the component and structure of 'new C' input into the soil by rhizosphere deposition in C assimilation and its relationship with oxidation and mineralized stability should also be accounted for. [ABSTRACT FROM AUTHOR]

Organic farming largely depends on animal manure as a source of phosphorus (P) and the recycling of animal manure globally is becoming increasingly important. In a pot experiment, using radioactive P labeling techniques, we studied ryegrass uptake of P applied with animal manure and water soluble mineral fertilizer to soils that had been cropped for 22 years according to organic or conventional farming practices. The soils differed in P status and microbial activity. Labeling soil-available P also allowed assessing the uptake from residual P that remained in the soils because of their different fertilization histories. On each soil, recovery of fresh manure P in four harvests of ryegrass shoots was lower than recovery of mineral P. It ranged from 24% to 35% for manure P and from 37% to 43% for mineral P. Recovery of fresh manure P was affected by soil-available P contents. It was lower at a higher available P in a conventional soil. Different levels in microbial activity among soils were of lesser importance for the recovery of fresh manure P in plants. The recovery of residual P ranged from 9% to 15%. Residual P contained in organic cropped soils contributed less to P nutrition of ryegrass than the residual P contained in conventional cropped soils, probably due to their lower residual P contents being composed of stable P forms. The indirect isotope dilution technique is useful in assessing manure P uptake by plants, but attention must be given to added P interactions, i.e., the potential impact of organic amendments on P uptake from non-labeled soil and residual P. [ABSTRACT FROM AUTHOR]

A field experiment was conducted to test the new approach for estimating crop nitrogen (N) uptake from organic inputs. The soil was prelabeled with 15N by applying 15N fertilizer to sunflower crop (Helianthus annuus L. var. Viki). The 14N plots, which received unlabelled fertilizer, were also set up. At harvest, 15N labeled residues were added to the unlabeled soils at a rate of 73 kg N ha-1 (direct technique) and unlabeled residues were added to the 15N-labeled soils at the same rate (indirect technique). Control plots without residues were also established. All plots were sown with the wheat (Triticum aestivum L. var merchouch)-fababean (Vicia faba L.)-wheat (Triticum aestivum L. var merchouch) cropping sequence. In the cropping sequence, the first, second and third crop derived respectively 12.01, 2.4, and 1.93 kg N ha-1 from crop residues estimated by the direct method and 14.77, 3.3, and 1.85 kg N ha-1 estimated by the indirect method. The results showed no significant difference between the two techniques, which suggests that the new soil prelabeling technique compares well with the direct technique. [ABSTRACT FROM AUTHOR]

The pharmacokinetics of dextro(+)- and levo(-)-verapamii were studied in five healthy volunteers following oral administration of pseudoracemic verapamii containing equal amounts of unlabelled (-)- and dideuterated (+)-isomer. (+)-verapamil exhibited approximately five times greater Cmax (+): 240 ± 81.1 ng/ml, (-): 46.1 ± 15.7 ng/ml, P < 0.001.) and AUC than (-)-verapamil. The apparent oral clearance (CLo) for (+)-verapamil was significantly smaller than that for (-)- verapamil (+): 1.72 ± 0.57 l/min, (-): 7.46 ± 2.16 l/min, P < 0.001). The bioavailability of (+)-verapamil (50%) was 2.5 times greater than that of (-)-verapamil (20%), P < 0.005). Thus following oral administration verapamil exhibited a stereoselective first-pass metabolism. Neither tmax nor the elimination t½,z were different between the isomers. The elimination of t½,z for each verapamil isomer obtained.following oral administration (+): 4.03 h, (-): 5.38 h) were similar to those previously obtained following intravenous administration (+): 4.15 h, (-): 5.38 h, respectively). Whereas the (+)- to (-)-verapamii plasma concentration ratio following oral administration was 4.92 ± 0.48, the ratio following i.v. administration was approximately 2. (-)-verapamil has been demonstrated to possess 8 to 10 times more potent negative dromotropic effect on AV conduction than (+)-verapamil. Therefore, following oral administration the same concentration of plasma verapamil consisting of a two to three times smaller proportion of the more potent (-)-isomer appeared to be less potent than that following i.v. administration with regard to the negative dromotropic effects on the AV conduction. [ABSTRACT FROM AUTHOR]

In recent years, the field of AMS has expanded into many areas of science. This paper reviews a variety of applications of AMS in the marine environment, focusing particularly on recent developments and applications. Following a brief summary of the three main isotope techniques used in environmental studies: dating, tracing and source identification, a number of applications are considered. Traditional 14C-dating is no longer the dominant application of AMS measurements, and together with measurements of 10Be, 26Al and 36Cl, much of the research is now directed towards an understanding of global climate change via studies of oceanic circulation, atmospheric processes and past climates by cosmic ray exposure dating. Profiles of long-lived cosmogenic radionuclides in sediments and ice cores, as a function of depth and, thus, age, provide key information on past solar variability, production rate changes and atmospheric transport and deposition mechanisms. Useful paleoclimatic information may be derived from these archives both because deposition is influenced by climate and because solar activity (which influences production) and solar radiance (which influences climate) are correlated. In recent years, emphasis has been put on the development and application of AMS techniques for the measurement of heavier long-lived isotopes, including 99Tc, 129I, 236U and other actinide isotopes. AMS combines ultra low detection limits and the possibility to analyse isotope ratios that can be difficult with traditional instruments and has been used in a number of applications on the consequences and uses of releases from nuclear energy. Finally, the use AMS in environmental sciences is expected to expand further in the foreseeable future with long-lived cosmogenic radionuclides contributing to a large body of knowledge on processes involving atmosphere, oceans, ice sheets, biosphere, soils and sediments. [Copyright &y& Elsevier]

Soil phosphorus (P) deficiency is a major factor limiting crop productivity in many tropical and subtropical soils. Due to the acidic nature of these soils, rock phosphate (RP)-based P fertilizers that are cheaper than manufactured water-soluble P fertilizers can be an attractive alternative under certain conditions. Assessment of the efficacy of these alternative P fertilizers and a rational management of local P resources for sustainable agricultural production require an understanding of the dynamics of P in the soil–plant system and the interactions of various P sources in soils and monitoring of soil available P levels. The present work was conducted to test the applicability of the 32P isotopic kinetic method to assess the soil P fertility status and evaluate the agronomic effectiveness of local rock phosphates in subtropical China. A series of experiments was carried out in the laboratory, greenhouse and field conditions with the following specific objectives: (a) to evaluate the suitability of this isotopic kinetic method in evaluating soil P fertility in 32 soil samples collected across southern China, (b) to test and further develop chemical extraction methods for routine soil P testing, (c) to monitor the dissolution kinetics of local low to medium grade rock phosphate sources and their effect on soil properties and (d) to evaluate their agronomic effectiveness in greenhouse and field experiments. Since most of the studied soils had very low concentrations of soluble P and high P-fixing capacities, the isotopic kinetic method was found unsuitable for evaluating soil P fertility and to predict plant P uptake. In contrast, the proposed chemical extraction method (NaHCO3-NH4F) predicted very well plant P uptake, suggesting that this extraction method can be routinely used to evaluate soil bioavailable P in similar soils in subtropical China. From the incubation study, it was found that although the local low to medium grade RPs were inferior to the reactive NCPR in increasing soil available P levels, they have the potential to improve soil chemical properties. Field experiments indeed demonstrated that the medium grade Jinxiang RP significantly increased crop yield, suggesting that local low to medium grade RPs could be used as P sources to provide P to plants and also to improve soil chemical properties. Overall, these results provide important information for a rational management of P resources for sustainable agriculture in subtropical China. [ABSTRACT FROM AUTHOR]

Using the isotope techniques, the groundwater origin, evolution and circulation in the potential site of China's high-level waste repository are studied. The results indicate that both shallow groundwaters and deep groundwaters in the site area are of meteoric origin. The shallow groundwaters are mainly recharged by modern and local precipitation, and the deep groundwaters are originated from regional precipitation at higher elevation, or may be from the precipitation during the geological history period with lower temperature. Through the study we can also understand that the deep underground is a very low-permeability system where the groundwater flow-rates are very low. [ABSTRACT FROM AUTHOR]

Owing to a lack of efficient solid waste management (SWM) systems, groundwater in most developing countries is found to be contaminated and tends to pose significant environmental health risks. This review paper proffers guidelines on the application of isotopic techniques to trace groundwater pollution sources from data spanning from 2010 to 2020 within developing countries. Earlier groundwater studies in those countries were mainly focused on using hydrochemical and geophysical techniques. The limitation of these techniques is that they can only monitor the concentration of pollutants in the water bodies and possible leachate infiltration but cannot determine the specific sources of the pollution. Stable isotopes of δ18O, δ2H and δ13C can confirm leachate migration to water bodies due to methanogenesis. The high tritium in landfill leachates is useful to identify leachate percolation in groundwater. The δ15N technique has been used to distinguish between synthetic and organic nitrogen sources but its application is limited to differentiating between atmospheric vs. inorganic nitrogen sources. The use of a dual isotope of δ15N– NO 3 − and δ18O– NO 3 − is beneficial in terms of identifying various sources of nitrogen such as atmospheric and inorganic fertilizers but is yet to be used to differentiate between nitrogen pollution sources from dumpsites, sewage and animal manure. The coupling of the 11B isotope with δ15N– NO 3 − and δ18O– NO 3 − and other hydrochemical parameters has proven to be effective in distinguishing between nitrate fertilizer, animal manure, seawater contamination and sewage. Therefore, in areas affected by agricultural activities, landfill leachates, domestic or sewage effluent and seawater intrusion, it is incumbent to couple hydrochemical ( Cl − , NO 3 − , B, DO) and isotope techniques (δ18O, 2H, δ13C, δ18O– NO 3 − , δ15N– NO 3 − , δ11B and 3H) to effectively determine pollution sources of groundwater in developing countries. The foregoing review will provide guidelines for studies that may aim to critically distinguish between seawater intrusion, dumpsites, sewage and septic leachates. [ABSTRACT FROM AUTHOR]

Copyright of Zeitschrift für Ernäehrungswissenschaft is the property of Springer Nature and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

A sound understanding of nutrient dynamics in ecosystems is required in order to manage these systems on a sustainable basis. A valuable approach to studying phosphorus (P) dynamics in soil-plant systems has been the use of P isotope techniques. Isotope techniques used for studying P cycling in agricultural and forest soils are reviewed in this paper with particular reference to advances made in the part 15 years. A brief discussion of the properties of P isotopes and their measurements is included together with techniques for measuring exchangeable P in the soil, dissolution and decomposition rates of inorganic and organic P sources applied to the soil, rates of organic P immobilization and mineralization, rates of P release and retention in the soil, root activity and lifter decomposition rates in forest soils, and gene probing and hybridization. Basic principles, assumptions, procedures, limitations and merits of methods are discussed. These techniques have served as or have the potential to be valuable tools for advancing our understanding of P dynamics in soil-plant systems, and for studying the molecular characteristics of microbial communities in relation to the cycling of nutrients in the soil. [ABSTRACT FROM AUTHOR]

In Chile, erosion processes (on-site and off-site impact) affect at least 36.9 million ha -1 , representing 49% of the total land area. Different regions show severe soil degradation mainly caused by water erosion processes. The importance of sediment-associated transport and the key role of soil erosion affect the fertility of the land and the contamination of water bodies. The aim of this work was to estimate the erosion rate, caused by the rainfall in Apalta vineyards in the Libertador General Bernardo O'Higgins Region of Chile using isotope techniques, assessing the 7 Be runoff during four years (2009-2012). The 7 Be distribution mass depth at a reference site ranged from 7 to 24 kg m -2 in the first two centimetres soil layer. Even when the vineyards have been well managed, the topographic characteristics and the climatic conditions facilitated soil erosion, with average rates of 50.4, 23.5, 50.6 and 67.3 tons ha -1 y -1 in 2009, 2010, 2011 and 2012, respectively. The robustness of the 7 Be technique demonstrated the advantage of a non-soil-destructive methodology to calculate soil distribution and erosion rates.

Minable rock phosphate is a finite resource. Replacing mineral phosphorus (P) fertilizer with P-rich secondary resources is one way to manage P more efficiently, but the importance of physicochemical and microbial soil processes induced by secondary resources for plant P uptake is still poorly understood. Using radioactive-labeling techniques, the fertilization effects of dairy manure, fish sludge, meat bone meal, and wood ash were studied as P uptake by barley after 44 days and compared with those of water-soluble mineral P (MinP) and an unfertilized control (NoP) in a pot experiment with an agricultural soil containing little available P at two soil pH levels, approximately pH 5.3 (unlimed soil) and pH 6.2 (limed soil). In a parallel incubation experiment, the effects of the secondary resources on physicochemical and microbial soil processes were studied. The results showed that the relative agronomic efficiency compared with MinP decreased in the order: manure ≥fish sludge ≥wood ash ≥meat bone meal. The solubility of inorganic P in secondary resources was the main driver for P uptake by barley (Hordeum vulgare). The effects of secondary resources on physicochemical and microbial soil processes were of little overall importance. Application of organic carbon with manure resulted in microbial P immobilization and decreased uptake by barley of P derived from the soil. On both soils, P uptake by barley was best explained by a positive linear relationship with the H2O + NaHCO3-soluble inorganic P fraction in fertilizers or by a linear negative relationship with the HCl-soluble inorganic P fraction in fertilizers.