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Abstract The objective of this study was to evaluate the leaching potential of P from a range of sewage sludge‐ or P fertilizer (monocalcium phosphate)‐amended topsoils that had different P contents. Leaching trials (70 d) were conducted in 30‐cm‐long PVC columns; P‐related parameters were then determined at different depths in the leached soils. In most cases, more ( P sludge > control. At the lowest depth (16–20 cm) of the leached soil, the degree of P sorption saturation decreased in the same order and was related curvilinearly ( P < 0.001) to cumulative P leached (at 70 d). This relationship demonstrates the importance of P sorption saturation in controlling P leaching in sludge‐ and fertilizer‐treated soils. The more rapid rate of P saturation and P leaching in P‐fertilized than sludge‐treated soils emphasizes the role of the P source in adsorption‐desorption processes.
Siddique et al. (Wed,) studied this question.