Differential Effects of Organic Amendments on Soil P Availability, Plant P Uptake Efficiency and Root Traits of Durum Wheat at its Earliest Stage in Calcareous and Non-Calcareous Soils: A Microcosm Approach

Abstract This study assesses the effect of commonly used organic amendments on soil phosphorus (P) availability, P uptake, growth and root traits of durum wheat seedlings grown in two soils with contrasting properties. After a phytotoxicity assay developed to evaluate potential negative effects on plant growth, durum wheat was grown in soil microcosms amended with composted olive mill pomace (COP), vermicompost (VEC), compost from solid anaerobic digestate (DIG) or municipal solid waste compost (CSW) at an equivalent dose of 30 mg P kg −1 . Diammonium phosphate and no P application were included as positive and negative control. A calcareous Vertisol and a non-calcareous Luvisol were used to evaluate alterations in soil (pH, electrical conductivity, available P) and plant responses (leaf chlorophyll content, biomass, P uptake, root traits, nutrient contents) after a 21-d growing period. Tested organic amendments were non-phytotoxic. In the microcosm experiment, DIG and CSW produced the largest soil P availability (22.7–28.6% higher than control treatment-CON) and P uptake efficiency (3.2–5.1%) in both soils. In comparison with CON, DIG increased the total (+ 82.9%) and specific root length (+ 104.0%) in both soils, while VEC stimulated the specific root length (+ 39.4%) in the calcareous soil only. COP, VEC and CSW negatively affected root traits in wheat seedlings growing in the non-calcareous soil, as well as leaf chlorophyll content and / or plant height in both soils. DIG and CSW were a reasonable alternative to inorganic fertilizers in the soils tested in terms of P provision and uptake efficiency, and in soil exploration. Graphical Abstract