The effect of reducing conditions on the solubility of phosphorus in a diverse range of European agricultural soils

Abstract

Summary The effects of reducing conditions on solubility of phosphorus (P) can directly influence water quality. The release of P is enhanced although the P is not directly involved in reduction processes. We here compare the responses to flooding of 12 overfertilized agricultural soils in widely varying pedological and management regimes, belonging to seven World Reference Base groups. The redox potential initially ranged from 305 to 515 mV and decreased to −157 to −195 mV within 32 days. The onset of reducing conditions led to an increase in the concentration of soluble P. The maximum rate of solubilization occurred within 1–3 weeks under reducing conditions, and the steady‐state concentrations of P never exceeded 200 μmol dm−3. Four stages in the development of the reduction process are identified, and a simple empirical model describes the change in concentrations of soluble P. The potential of P release under reduction is positively correlated with the soil saturation with P. Flooding over a few weeks triggered the release of large amounts of P. Constant pe + pH is related to constant concentration of molybdate‐reactive P, suggesting that soluble P is effectively buffered so that P will be immobilized. In general the solubilization of P under reducing conditions is likely to be aggravated by the increased soil P status that has resulted from overfertilization of agricultural land with P. These findings bear on the establishment and long‐term effectiveness of riparian buffer zones where phosphorus is likely to accumulate by the interception of drainage.

Cadaver decomposition in terrestrial ecosystems

“…Gravesoil associated with adipocere formation was observed to contain elevated levels of dissolved organic C, plant available P and total P (Fiedler et al 2004) relative to soils without adipocere. While acidic soil can promote the leaching of P from bone (Eidt 1977), significant amounts can also be released from soil saturated with P (such as gravesoils) under reducing conditions (Scalenghe et al 2002). This release is enhanced by the presence of organic carbon, which acts as the primary electron donor (Scalenghe et al 2002).…”

Aspects of phosphorus transfer from soils in Europe

“…The loss of inorganic P sorption surfaces starts in soils with moderate reduction (Miller et al, 2001) and later the soil solutions contain enough Fe to effectively retain the released P by means of coprecipitation or adsorption onto newly formed Fe hydroxides as the solution encounters oxidized conditions (Shenker et al, 2005;Ajmone Marsan et al, 2006). As redox reactions influence indirectly the soil P chemistry through effects on the solubility of Fe and Mn minerals and the associated changes in pH affect the Ca phosphate solubility, the change in P concentration during a redox cycle depends on a combination of the shifts of redox potential and pH (Scalenghe et al, 2002). Despite a wide range in soil basic characteristics, the responses to reducing conditions could be remarkably similar when P release is interpreted using a simple empirical expression based on redox-sensitive soil properties (organic C, Fe crystallinity ratio, total Ca carbonate, and oxalate-…”

“…They have been found to be effective in reducing the export of particulate pollutants when the integrity of the system is maintained (Dabney et al, 2006). However, these agroforestry buffers could be of limited utility if reducing conditions enhance the solubilization of P retained in the strip as revealed by Scalenghe et al (2002). In addition, in climates where the majority of runoff occurs during frozen-ground conditions, vegetative buffer strips alone are unlikely to dramatically reduce runoff and nutrient loading into surface waters (Steinke et al, 2007).…”

Reversibilidade do fósforo não-lábil em solos submetidos à redução microbiana e química: I - alterações químicas e mineralógicas

“…Os valores de Eh e de pH para E1 (Quadro 2) apresentam-se semelhantes aos encontrados na literatura sobre efeito de ambiente redutivo proporcionado por inundação (Scalenghe et al, 2002;Meissner et al, 2008). Ao aumentar o tempo de contato para 60 dias (E4), com trocas de soluções aos 30 dias (E2) e aos 45 dias (E3), os valores de Eh, de modo geral, voltam a aumentar.…”