Availability and Transformation of Applied Phosphorus In Calcareous Lebanese Soils

Abstract

Though the initial reactions of P in soils are important with respect to plant growth and efficient fertilizer use, the reactions that occur with time have received less research attention, and may have even more important implications for these aspects. In order to monitor changes in applied P after fertilization, six calcareous soils were incubated up to 200 d with P solutions and periodically extracted with NaHCO3, and inorganically fractioned. Soil batches were equilibrated with P solutions ranging from 0 to 40 mg P L−1 for adsorption isotherm data after 0, 60, and 200‐d incubation. Desorption curves were obtained by water extraction for eight consecutive days. Extractable P values declined rapidly within the first day, and uniformly thereafter. The amounts of P retained against NaHCO3 extraction were closely related to citrate‐dithionite‐bicarbonate (CDB)‐Fe. With the longer incubation period, generally less P was released in the water extraction. Similarly, desorbed P was inversely related to CDB‐Fe. While P additions mainly enriched the NH4Cl‐ and NaOH‐P fractions, the amounts recovered decreased with time. Increasing prior soil‐P contact time also caused a shift in the adsorption isotherms, reflecting changes in retained P and the soils' retention capacity. Thus, free Fe oxides may modify longer‐term P reactions and residual P availability in CaCO3‐rich soils.

Soil and Fertilizer Phosphorus and Crop Responses in the Dryland Mediterranean Zone

“…Indeed, in Mediterranean soils, Fe oxides seem to be involved in long-term P sorption. Ryan et al (1985b) found, for six Lebanese soils, that the decrease in P extractability with time was related to Fed. Torrent (1987) found that the slow sorption for a group of 20 clays of Mediterranean soils could be described by a modified Elovich equation (C = Co -qt), the slope of which, q, was correlated with Fed.…”

Phosphate Utilization Efficiency Correlates with Expression of Low-Affinity Phosphate Transporters and Noncoding RNA, IPS1, in Barley

“…Basal nutrients and plant growth conditions were as described by Genc et al (2007). Calcium carbonate powder (0.5%, w/w) was added in the sand to simulate calcareous sandy soil and to reduce P availability (Ryan et al, 1985;Westermann, 1992). Three P rates (7.5, 22.5, and 75 mg P kg 21 sand as KH 2 PO 4 ) were used in the experiments for severely P-deficient, moderately P-deficient, and P-adequate plants, respectively.…”

Chemical and textural controls on phosphorus mobility in drylands of southeastern Utah

“…Smaller particles form tighter bonds with P because they have more surface area (Carreira et al 2006). Amorphous minerals tend to sorb P more rapidly than crystalline material for similar reasons (Ryan et al 1985). Distinctions concerning the type and intensity of P bonding are important because these issues address the mobility and plant availability of P in dryland soil.…”