Phosphorus availability of sewage sludges and ashes in soils of contrasting pH
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Background:Little is known about the relationship between plant availability of P in different sludges and their derived ashes, its development over time and its interaction with soil pH. Aim:This study addresses this knowledge gap, by investigating the P availability and fractions of six sludges produced under different conditions and the incineration ashes derived from five of these,plusthe effect of time (84 days) and soil pH on P availability. Methods:These materials were applied to two similar soils with contrasting pH (5.8 and 7.8), based on the assumption that lower pH would favor plant availability of P from these sources. Triple super phosphate and a control (no P addition) were included as references. Results:The relative P fertilizer availability (RFA) in soil of both sludges (18-77%) and ashes (0.1-25%), measured as water extractable P, was found to be highly dependent on their origin. While the P availability of sludges was strongly affected by soil pH, ash P availability showed either no or little soil pH effect, in contrast to our expectations. For the sludges, RFA was negatively correlated to the ratio (Fe+Al)/P in both pH soils and positively correlated to sludge water extractable P in the higher pH soil. For the ashes, the ratio Fe+Al to P and the pH reaction of ashes in water were strongly negatively correlated with RFA in the lower pH soil. Ca/P ratios did not predict RFA in either sludges or ashes. Nevertheless, we ascribe the comparably higher average RFA in sludges of 58% found in the low pH soil compared to 25% in the alkaline soil to the greater solubility of Ca-P species under lower pH. For ashes, the availability increased over time, while rather stable for sludges. Conclusion:In conclusion, the P availability of both sludges and ashes was highly dependent on their origin, and for sludges highly dependent on soil pH
Original language | English |
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Journal | Journal of Plant Nutrition and Soil Science |
Volume | 183 |
Issue number | 6 |
Pages (from-to) | 682-694 |
Number of pages | 13 |
ISSN | 1436-8730 |
DOIs | |
Publication status | Published - 2020 |
- P availability, sludges, sludge ashes, soil pH, FLUIDIZED-BED GASIFICATION, FERTILIZER VALUE, WASTE-WATER, PLANT AVAILABILITY, CROP, PHYTOAVAILABILITY, BIOAVAILABILITY, MANAGEMENT, PRODUCTS, DYNAMICS
Research areas
ID: 250379339