Characterizing phosphorus forms in Saskatchewan soils using solution 31P NMR spectroscopy

Non-Peer ReviewedIn soils and other environmental samples, phosphorus (P) may be found in a range of inorganic and organic forms. Inorganic P forms include orthophosphate, which is readily available to plants, and complex inorganic P forms such as pyrophosphate and polyphosphate. Organic P forms can be divided into groups such as orthophosphate monoesters (e.g. sugar phosphates, phytic acid) and orthophosphate diesters (e.g. phospholipids, DNA) and phosphonates. Identifying P forms is important to enhance crop growth, with and without fertilization, and to minimize P loss to water, where it can cause harmful algal blooms. This presentation describes some of our recent research using solution 31P NMR spectroscopy to characterize P forms in a range of Saskatchewan soils, as well as swine manure

Effect of freeze-thaw cycles and soil water content on infiltration rate of Saskatchewan soils

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Phosphorus export as influenced by placement method in two contrasting sites in south-central Saskatchewan

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Phosphorus forms and concentrations in soils under different land use in southwestern Saskatchewan

Non-Peer ReviewedPhosphorus (P) is an essential nutrient for all organisms. Insufficient or poorly available P can limit crop growth, requiring P fertilization. However, excess P can move from land to water, impairing water quality. Balancing P fertilization to maximize crop growth while limiting P loss requires a detailed knowledge of P forms and cycling. Different land use practices are expected to alter P cycling through differences in microbial populations, P inputs from vegetation and fertilizer, and management practices that affect soil chemical and physical properties. Understanding P cycling under different land uses can help to improve P use efficiency in agriculture. Presented here are the preliminary results of a research project investigating P forms and cycling in soils under different land uses in southwestern Saskatchewan

Forecasting the quality of AMF communities

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Organic phosphorus composition and potential bioavailability in semi-arid arable soils of the Western United States

The organic P composition of semi-arid arable soils is largely unknown, but such information is fundamental to understanding P dynamics in irrigated agriculture. We used solution "P nuclear magnetic resonance (NMR) spectroscopy and phosphatase hydrolysis to characterize organic P in semi-arid arable soils from the western USA (organic C 2.0-30.7 g C kg' soil, clay 2-48%, pH 5.2-8.2, CaCO 3 <1-480 g kg -' soil). Total P concentrations ranged from 220 to 1210 mg P kg-1 soil, of which between 12 and 45% was extracted with NaOH-EDTA. Inorganic orthophosphate was the dominant P compound, but concentrations determined by solution 31P NMR spectroscopy were consistently greater than those determined by molybdate colorimetry. Concentrations of organic P were relatively small, and were dominated by orthophosphate monoesters (11-130 mg P kg-1 soil), with smaller concentrations of orthophosphate diesters (0-7 mg P kg-1 soil). Pyrophosphate was present in almost all soils at concentrations up to 14 mg P kg-1 soil. Bicarbonate-extractable organic P ranged from 1.7 to 22.8 mg P kg-1 soil, of which between 37 and 87% was hydrolyzed by phosphatase enzymes, suggesting its bioavailability. Soil organic P concentrations were positively correlated with mean annual precipitation, organic C, clay, and oxalate-extractable metals (Al, Fe, Mn), and negatively correlated with mean annual temperature and soil pH. However, CaCO3 concentrations were not significantly correlated with any soil property. These results indicate that equilibrium levels of organic P in semi-arid arable soils are controlled by a balance between the physical protection offered by the soil matrix and the suitability of the environment for biological productivit

Long-term response of spring wheat to N and P fertilization in southwestern Saskatchewan

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Editorial: Phosphorus Along the Soil-Freshwater-Ocean Continuum

Phosphorus (P) is an essential element for all organisms. However, there is a P paradox, whereby P concentrations considered deficient in some environments such as in agricultural soils are considered excessive in freshwater, where they trigger eutrophication (e.g., Sims and Sharpley, 2005 and references therein; Elser and Bennet, 2011; Lougheed, 2011). Geographical imbalances also occur, with excesses in Western Europe and North America and deficiencies in regions with highly weathered soils, such as sub-Saharan Africa. There is a strong link between soil P stores and P mobilization and transfer to receiving waters, termed the P transfer continuum (Haygarth et al., 2005). Ensuring adequate P for crop production while minimizing water quality degradation requires consideration of this continuum and an international, interdisciplinary approach. This research topic brings together P studies in soil science, lakes, rivers, estuaries, and oceans, with 74 authors from 12 countries in Asia, Europe, and North America, and identifies key priorities for future research

Phosphorus Forms in Sediments of a River-Dominated Estuary

Estuaries are biologically productive transition zones between land and sea that play a vital role in transforming, recycling, and sequestering nutrients and organic matter, thus influencing nutrient loading to coastal systems. Yet, the processes involved in phosphorus (P) transformation and cycling among inorganic and organic P forms are poorly known in estuaries. To better understand the potential for P transformation and sequestration, we identified P forms and estimated their contributions to total P in intertidal wetland sediments of a river-dominated estuary (Columbia River, Oregon, USA) using solution 31P nuclear magnetic resonance spectroscopy (P-NMR). Inorganic P forms dominated sediment P extracts throughout the estuary, with orthophosphate accounting for 71–84% of total extracted P. However, biologically-derived inorganic and organic P forms were also detected. Polyphosphates were found in sediment extracts throughout the estuary, contributing as much as 10% of extracted P. Similar to other wetlands, orthophosphate monoesters and diesters made approximately equal contributions (~ 20%) to total extracted P. However, monoesters (e.g., phytate) were more abundant in sedimentary environments characterized by low organic matter content, while diesters (e.g., DNA) were more abundant in sedimentary environments with high organic matter, regardless of salinity. Collectively, the data show strong evidence for P transformation in sediments of a large, river-dominated estuary, which influences its transport to the coastal Pacific Ocean via the expansive Columbia River plume