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Over a dozen soil phosphorus (P) extraction procedures have been designed for agri-environmental purposes (P-tests). Sustainable expansion of agriculture into boreal regions dominated by Podzols requires further insights into P extractability. We extracted P from Podzol samples (n = 96) using nine P-tests followed by both colorimetric (PCol) and inductively coupled plasma (PICP) quantifications and assessed the relationships between P-tests. Samples were collected by depth or horizon from agricultural fields and reference sites in eastern, central, and western Newfoundland, Canada. The soil P was extracted with water, citric acid, ammonium bicarbonate diethylenetriaminepentaacetic acid (AB-DTPA), Morgan, Olsen, Bray-1, Bray-2, Mehlich-1, and Mehlich-3 solutions, thus targeting a wide range of extractable P pools in managed and natural Podzols. The soils had a pH of 3.4-6.9, organic matter of 0.5%-47.2%, and Al-M3 of 977-2561 mg kg-1. On average, water extracted the lowest PCol (1.0) and PICP (5.7) mg kg-1, while citric acid extracted the highest PCol (151) and PICP (290) mg kg-1. For the managed podzolic soils, the extractability of P followed the sequence water < Morgan < AB-DTPA < Mehlich-1 < Bray-1 < Mehlich-3 = Olsen = Bray-2 < citric acid; this varied slightly by quantification techniques and soil groups. The differences between PICP and PCol were most significant for the citric acid extracts. Most P-tests measurements were moderately to strongly correlated to P-M3ICP measurements (r2 > 0.50) but variable with quantification techniques and soil depths. Given the diversity in extractable P pools across management-induced soil conditions, it is evident that a fully informed P management for the Newfoundland Podzols will require calibration of P-tests against crop P uptake. [ABSTRACT FROM AUTHOR]

Rock pulverization is recommended when converting boreal forests to agricultural land use to facilitate tillage operations. Resulting rock dust incorporation might alter physical, chemical, and biological properties of soils. We assessed soil nematode trophic group abundances and indices, basal and burst respiration, and phosphorus extractability after land use conversion (LUC) and recent pulverization (<1 year) on three soil types in eastern Newfoundland, Canada. Nine treatments representing varied pulverization statuses (managed pulverized, managed unpulverized, natural) were nested in soil type (Podzol, Luvisol, and Organic). Conversion to agriculture impacted soil quality more than the recent rock pulverization. Nonetheless, nematode indices (fungivore/bacterivore, fungivore/fungivore+bacterivore, fungivore + bacterivore/herbivore) suggested no significant functional differences with either LUC or pulverization. Soil organic matter (SOM) and pH were substantial direct and indirect drivers of nematode community composition and soil respiration, mainly by altering availability of aluminium and iron. The functional parameters diverged between Organic and mineral soils. For all soils, most respiration parameters were significantly related to SOM, pH, available iron and aluminium. For nematodes, significant relationships were identified in the Organic soil: bacterivores and fungivores abundances were inversely related to SOM, and bacterivore abundance was positively related to pH. While for the mineral soils, citric acid extracted more phosphorus than the Mehlich-3 or water methods, Mehlich-3 was most effective for the Organic soil. Pulverization did not affect phosphorus extractability. The distinct relationships between soil quality properties and functional parameters between mineral and Organic soils are of interest for further investigations into the concepts of soil quality and soil health. Quand on souhaite adapter la forêt boréale à l'agriculture, on préconise de pulvériser le roc pour faciliter les labours. L'incorporation de la poussière rocheuse au sol peut cependant en altérer les propriétés physiques, chimiques et biologiques. Les auteurs ont évalué l'abondance des groupes trophiques de nématodes dans le sol et leurs indices, ainsi que le taux de respiration de base, l'explosion oxydative et l'extractabilité du phosphore après conversion de la vocation des terres (CVT) et pulvérisation récente du roc (moins d'un an) pour trois types de sol de l'est de Terre-Neuve, au Canada. Ils ont combiné différents degrés de pulvérisation (gestion de la pierre pulvérisée, gestion de la pierre non pulvérisée, état naturel) et types de sols (podzols, luvisols et sols organiques) en neuf traitements. La conversion en terre agricole a plus d'impact sur la qualité du sol que la pulvérisation récente du roc. Malgré cela, les indices des nématodes (fongivore/bactérivore, fongivore/fongivore+bactérivore, fongivore+bactérivore/herbivore) laissent croire qu'il n'existe aucune différence sensible entre la CVT et la pulvérisation, sur le plan fonctionnel. La matière organique du sol (MOSL) et le pH sont d'importants paramètres qui affectent directement et indirectement la composition de la population de nématodes et la respiration du sol, essentiellement parce qu'ils modifient la disponibilité de l'aluminium et du fer. Les paramètres fonctionnels ne sont pas les mêmes pour les sols organiques et les sols minéraux. Dans tous les sols, la majorité des paramètres de la respiration présentent une relation significative avec la MOS, le pH ainsi que la quantité de fer et d'aluminium disponible. Les auteurs ont établi des liens significatifs entre les nématodes et le sol organique : l'abondance de nématodes bactérivores et fongivores est inversement reliée à la quantité de MOS, alors que la population de bactérivores est positivement corrélée au pH. En revanche, dans les sols minéraux, l'acide citrique extrait plus de phosphore que la méthode Mehlich-3 ou l'extraction à l'eau, tandis que la technique Mehlich-3 s'avère plus efficace pour le sol organique. La pulvérisation ne modifie pas l'extractibilité du phosphore. Les liens évidents entre les propriétés qualitatives et les paramètres fonctionnels des sols minéraux et organiques mériteraient qu'on entreprenne des recherches plus poussées sur les concepts que sont la qualité et la vitalité du sol. [Traduit par la Rédaction] [ABSTRACT FROM AUTHOR]

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