Rhizosphere effects on Cu availability and fractionation in sewage sludge‐amended calcareous soils

Abstract

Rhizosphere processes have a major impact on copper (Cu) availability and its fractions in soils. A greenhouse experiment with wheat was performed to investigate availability (using seven chemical procedures) and fractionation of Cu in the rhizosphere of ten agricultural soils (Typic Calcixerepts) amended with sewage sludge (1% w/w) using rhizoboxes. The results show that available Cu concentrations in rhizosphere soils were significantly (P < 1%) lower than in bulk soils. In comparison with the bulk soils, in the rhizosphere soils the concentration of Cu associated with organic matter and residual Cu increased by 24 and 4%, respectively, whereas exchangeable Cu, Cu associated with iron-manganese oxides, and Cu associated with carbonate decreased by 20, 14, and 12%, respectively. Dissolved organic carbon (DOC) and Cu associated with iron-manganese oxides and Cu associated with organic matter in the rhizosphere and bulk soils were significantly correlated (P < 5%). The results show that the differences between rhizosphere and bulk soils in chemical conditions such as DOC concentrations can change the proportion of soil Cu fractions and, therefore, Cu availability for wheat in calcareous soils amended with sewage sludge. The results show that the wheat root-induced modifications of chemical and biological soil conditions do not only lead to Cu depletion in mobile soil Cu fractions, but also to modification in soil Cu fractions which are commonly considered as more stable.

Effect of the Long-Term Application of Sewage Sludge to A Calcareous Soil on Its Total and Bioavailable Content in Trace Elements, and Their Transfer to the Crop

“…However, the differences observed for soil Cu concentrations between doses were not observed in grain (Table 6). This could be explained by what was observed by Montaghian [91], who found that in calcareous soils amended with SS, the concentration of bioavailable Cu was lower in the soil of the rhizosphere than in the rest of the soil. They observed a redistribution of Cu between the different soil fractions, increasing the proportion linked to organic matter as a consequence of an increase in dissolved organic carbon released by the roots.…”

Seven years of pig slurry fertilization: impacts on soil chemical properties and the element content of winter barley plants

“…Copper concentrations in barley (Tables 5 and 6) were within the lowest range of normal Cu concentrations (from 3-20 mg kg −1 of dry foliage) according to Chaney (1989) which means that slurries were not able to improve plant Cu availability and differences with time may be attributed to a dilution effect similar to that found for other elements. According to Montaghian and Hosseinpur (2015), in calcareous soils amended with sewage sludges, there is a redistribution of Cu between different soil fractions, increasing the proportion linked to organic matter. However, final Cu extractions by barley plants increased with slurry fertilization (Fig.…”

“…Previous research on the effects of pig slurry application on soil HM (Provolo et al, 2018) or on other aspects, such as N efficiency (Bosch-Serra et al 2015) and N uptake and losses (Ovejero et al 2016), has been conducted over a relatively low number of cropping seasons. However, research has studied acid or neutral soils (Veiga et al 2012;Tiecher et al 2013;Oliveira et al 2014;Qaswar et al 2020), irrigated systems (Martínez et al 2017), or it has developed under greenhouse conditions (Montaghian and Hosseinpur 2015;Provolo et al 2018). Information about impacts on calcareous soils under field conditions in semiarid rainfed areas is scarce.…”