Continuous crop expansion has led to a growing demand for phosphate fertilizers. A sound knowledge of the dynamics of phosphorus, and its interaction with iron oxides and organic matter, can be useful to develop effective strategies for sustainable management, especially in a scenario of increasing shortage of mineral phosphate resources. In this paper, we review the relationship of phosphate to iron oxides and organic matter, and its effect on phosphorus availability. Crops typically obtain phosphate from weathered minerals and dissolved fertilizers. However, the amount of phosphorus present in the soil solution depends on the extent to which it is adsorbed or desorbed by iron oxides, which may be influenced by interactions with organic matter. Therefore, systems for fertilizer recomendation based on methodologies considering interactions between soil components such as oxides and organic matter, and the phosphorus sorption capacity resulting from such interactions (e.g. residual P analysis), may be more reliable to ensure efficient, rational use of phosphate. A contínua expansão da produção agrícola tem levado a uma crescente demanda de fertilizantes fosfatados. O conhecimento da dinâmica do fósforo no solo e suas interações com óxidos de ferro e matéria orgânica podem ser uteis no desenvolvimento de estratégias eficientes para o manejo sustentável, especialmente em um cenário de crescente escassez de fontes de minerais fosfatados. Nesta revisão bibliográfica foi abordado a relação do fósforo com óxidos de ferro e matéria orgânica, e seu efeito na disponibilidade de fósforo. As culturas, normalmente, obtém fosfato de minerais intemperizados ou fertilizantes dissolvidos. No entanto, a quantidade de fósforo presente na solução do solo depende das reações de adsorção e dessorção por óxidos de ferro, as quais podem ser influenciadas por interações com a matéria orgânica. Portanto, os sistemas de recomendação de fertilizantes com base em metodologias que consideram as interações entre componentes do solo, tais como óxidos e matéria orgânica, e a capacidade de adsorção de fósforo, resultantes de tais interações (por exemplo, análise de P remanescente), pode ser mais confiável para garantir o uso eficiente e racional de fertilizantes fosfatados.

Forms oF InorganIc PhosPhorussummary the cultivation of crops with different capacity of P uptake and use under long-term soil tillage systems can affect the distribution of P cycling and inorganic forms in the soil, as a result of higher or lower use efficiency of P applied in fertilizers. the purpose of this study was to evaluate the effect of long-term cultivation of different winter species under tillage systems on the distribution of inorganic P forms in the soil. In 1986, the experiment was initiated with six winter crops (blue lupin, hairy vetch, oat, oilseed radish, wheat and fallow) on a rhodic hapludox in southwestern Paraná, under no-tillage (nt) and conventional tillage (ct). the application of phosphate fertilizer in nt rows increased inorganic P in the labile and moderately labile forms, and soil disturbance in ct redistributed the applied P in the deeper layers, increasing the moderately labile P concentration in the subsurface layers. Black oat and blue lupin were the most efficient P-recyclers and under nt, they increased the labile P content in the soil surface layers.

In this paper we explore the accumulation of different phosphorus (P) fractions in soil submitted to successive applications of pig slurry (PS) and deep pig litter (DL). After 88 months of no-till crop cycles, soil samples were collected in the following treatments: control (C), PS applications equivalent to 90 and 180 kg N ha -1 (PS90 and PS180), and DL applications equivalent to 90 and 180 kg N ha -1 (DL90 and DL180). The cumulative application of P of the C, PS90, PS180, DL90 and DL180 treatment was 0, 303, 606, 825 and 1650 kg P ha -1 , respectively. The soil samples were then submitted to P chemical fractionation. Successive applications of 303 and 606 kg P ha -1 in PS form and 825 and 1.650 kg P ha -1 in DL form increased P levels down to 20 cm depth, especially in the labile inorganic fraction extracted by anion exchange resin and 0.5 M NaHCO 3 and to a lesser extent extracted by 0.1 M NaOH. Successive additions of PS180 and DL180 increased the levels of organic P extracted by 0.5 M NaHCO 3 , 0.1 M NaOH and 0.5 M NaOH, and successive applications of PS and DL caused P accumulation in the soil profile, especially in labile fractions. This increased the availability to plants, but also increases the potential for environmental contamination.

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Purpose This review of sediment source fingerprinting assesses the current state-of-the-art, remaining challenges and emerging themes. It combines inputs from international scientists either with track records in the approach or with expertise relevant to progressing the science. Methods Web of Science and Google Scholar were used to review published papers spanning the period 2013–2019, inclusive, to confirm publication trends in quantities of papers by study area country and the types of tracers used. The most recent (2018–2019, inclusive) papers were also benchmarked using a methodological decision-tree published in 2017. Scope Areas requiring further research and international consensus on methodological detail are reviewed, and these comprise spatial variability in tracers and corresponding sampling implications for end-members, temporal variability in tracers and sampling implications for end-members and target sediment, tracer conservation and knowledge-based pre-selection, the physico-chemical basis for source discrimination and dissemination of fingerprinting results to stakeholders. Emerging themes are also discussed: novel tracers, concentration-dependence for biomarkers, combining sediment fingerprinting and age-dating, applications to sediment-bound pollutants, incorporation of supportive spatial information to augment discrimination and modelling, aeolian sediment source fingerprinting, integration with process-based models and development of open-access software tools for data processing. Conclusions The popularity of sediment source fingerprinting continues on an upward trend globally, but with this growth comes issues surrounding lack of standardisation and procedural diversity. Nonetheless, the last 2 years have also evidenced growing uptake of critical requirements for robust applications and this review is intended to signpost investigators, both old and new, towards these benchmarks and remaining research challenges for, and emerging options for different applications of, the fingerprinting approach.

A B S T R A C TOrganic phosphorus (P) is an important source of phosphate for plants both in natural environments and in cultivated soils. Growing plants with high P recycling capacity may increase the importance of organic forms in phosphate availability mainly in undisturbed soils. The aim of this study was to evaluate the effect of long period of cultivation of different winter species under different soil management systems in the distribution of soil organic P forms, in the P content stored into the soil microbial biomass (SMB) and in the acid phosphatase enzyme activity. The experiment was established in 1986 with six winter treatments (blue lupine, hairy vetch, oat, radish, wheat and fallow) implanted in a Rhodic Hapludox in southern Brazil, under no-tillage system (NT) and conventional tillage system (CT). The crops were cultivated with rational use of chemical phosphate fertilizer, according to plant needs and soil type maintaining high levels of soil organic carbon leading to P organic form accumulation. Growing crops during the winter period in highly weathered subtropical soil increases the importance of microbial interactions in the P cycle, especially in the NT, where a large amount of crop residues is annually added to the soil surface, increasing soil organic P level, P content stored into the SMB and acid phosphatase enzyme activity.