Forms and Availability of Soil Phosphorus in Temperate Forests in Southern Chile and Flanders

Abstract

This study investigated the different forms and availability of P in soil profiles from temperate forests in southern Chile (two sites: Nothofagus obliqua (Mirb.) Bl. and Nothofagus betuloides (Mirb.) Oerst.) and Flanders, Belgium (two sites: Pinus nigra Arnold and Betula pendula Roth). Soils were sampled according to genetic horizonation and analysed for organic matter, oxalateextractable P, Al and Fe, total inorganic P and total organic P. Phosphorus availability was assessed using an isotopic exchange technique and anion exchange membranes. The total P content was higher for the Chilean andosols and remained relatively high in the whole soil profile (1413-187 mg P kg -1 ) whereas total P decreased sharply in the lower horizons of the Flemish podzols (575-4 mg P kg -1 ). There was a strong predominance of organic P in the Chilean soils (up to 90% of total P). The high volcanic activity in Chile is responsible for the large amounts of allophone, which entail high P-fixing capacities in these soils. Notwithstanding the much larger total P content in Chilean andosols compared to the Flemish podzols, both soil types feature comparable amounts of available P (AEM-P). The two phosphorus availability indices (IEP and AEM-P) correlated rather well for the Flemish forest sites (R² = 0.67), while the same correlation was lacking for the Chilean soil profiles (R² = 0.11). However, a strong relation between AEM-P and the organic matter content of the andosols emerged. The presence of Al and DOC in the AEM-extracts of eight selected Chilean soil samples suggests the extraction of organo-mineral colloids by the membrane. The lack of correlation between AEM-P and IEP for the Chilean soils may be related to the presence of these colloids, as they may lead to an overestimation of IEP as well as biased AEM-P values. Differences in forms and availability of phosphorus between the Chilean and the Flemish soil profiles were mostly ascribed to differences in soil properties rather than to differences in anthropogenic influences.KEYWORDS: Andosols, phosphorus availability, podzols RESUMEN Este estudio investiga las diferentes formas y disponibilidad de P en perfiles de suelo en bosques templados del sur de Chile (2 sitios: Nothofagus obliqua (Mirb) Blume y Nothofagus betuloides (Mirb.) Oerst) y Flanders, Bélgica (2 sitios: Pinus nigra Arnold y Betula pendula Roth). Los suelos fueron muestreados de acuerdo con los horizontes genéticos y analizados para materia orgánica, P oxalato-extraíble, Al y Fe, P inorgánico total y P orgánico total. La disponibilidad de fósforo fue evaluada utilizando una técnica de intercambio isotópico y membranas de intercambio aniónico. El contenido total de P fue más alto para los suelos andosoles en Chile y relativamente alto en el perfil completo del suelo (1413-187 mg P kg -1 ), mientras que el P total decreció pronunciadamente en los horizontes más bajos de los suelos podzoles de Flanders (575-4 mg P kg -1 ). Hubo una clara predominancia de P orgánico en los suelos chilenos (> 90% de P total). L...

Phosphorus fixing capacity of the Oxic Rhodustalf—alfisol soil in the Chotanagpur plateau region of Eastern India

“…This may be attributed to lower phosphorus content in the subsurface as well as presence of more organic matter in the surface as compared to subsurface soil. Organic matter on decomposition releases organic molecules, which form complexes with Fe and Al ions thereby blocking the sites which are mainly responsible for fixation of phosphorus [9][10][11]. This is supported by results of another experiment [12] conducted in the same site which showed that addition of organic manure markedly increased the availability of phosphorus in the soil.…”

Phosphorus fixing capacity of a volcanic soil on the slope of mount Cameroon

“…Organic molecules released on decomposition of organic matter form complexes with Fe and Al in the soil thereby blocking the sites which are mainly responsible for fixation of phosphorus in the soil (Juo and Fox, 1977;Subramanian and Kumaraswamy, 1989;Brouwere et al, 2003;Ghosal et al, 2011). Banik et al (2006) also showed that addition of organic manure markedly increased the availability of phosphorus in the soil.…”

Phosphorus fractions and phosphatase activity in an Andisol under different forest ecosystems

“…Indeed, in this study moderate labile P represented, on average, 64% of total P o whereas no labile P averaged 31% of total P o . Temperate Chilean forest soils have high contents of organic P (Thomas et al, 1999;De Brouwere et al, 2003), with most of this P present as moderate labile fraction like those forest Andisols reported by Binkley et al (2000) and Spears et al (2001).…”