Water soluble phosphate fertilizers for crops grown in calcareous soils – an outdated paradigm for recycled phosphorus fertilizers?

Abstract

Background and aimsThe current paradigm for phosphorus (P) fertilizers applied to calcareous soil is that almost entirely water soluble P fertilizers are efficient and sparingly soluble P fertilizers are not efficient P sources for crops. We hypothesize that this paradigm does not apply to recycled P fertilizers and that other P pools can explain the plant use of recycled P fertilizers on calcareous soil. Methods We applied 33 P isotopic dilution method to evaluate recycled P fertilizers based on plant P uptake from fertilizer relative to plant uptake from a water soluble P reference fertilizer. The predictability of fertilizer effectiveness based on sequentially extracted P forms and X-ray diffraction pattern of recycled fertilizers derived from sewage sludge, human urine and organic waste was evaluated. ResultsThe plant experiments showed that tested recycled P fertilizers including compost were more effective than rock phosphate. The water insoluble P contained in urine based products was almost as effective as a fully water soluble P fertilizer. The tested recycled P fertilizers are characterized by complex P compounds differing in solubility which were so far not considered in the water and citric acid extraction methods. The fraction of resin-and NaHCO 3 extractable fertilizer P explained effectiveness of P fertilizer applied to the calcareous and to an acidic soil. Conclusion We concluded that water solubility is not required when P forms in recycled products are comparable to reactions products of rock phosphate based fertilizers in soil. Alternatives to fully water soluble P fertilizers are available to supply P to crops grown on calcareous soil efficiently.

Predicting Phosphate Release from Sewage Sludge Ash Using an Ion Sink Assay

“…As DGT is sampling diffusive P, these results suggest that the potential of a fertilizer to sustain the P nutrition of a crop is related to its ability to release P to the soil solution. Meyer et al (2017) confirmed this by showing that the amount of fertilizer P that was sequentially extractable by resin and NaHCO 3 predicted well the amount of P derived from recycling fertilizer taken up by ryegrass using the approach of Nanzer et al (2014a). Alt et al (2013) and Andersson et al (2016) used combined additions of cation and anion sinks to study the kinetics of P release from alkaline soils.…”

Calcium Carbonate Packed Electrochemical Precipitation Column: New Concept of Phosphate Removal and Recovery

“…12 Furthermore, calcium phosphate has also recently been shown to be an effective fertilizer when compared to conventional fertilizers and struvite. 16…”

Urinals for water savings and nutrient recovery: a feasibility study

“…The primary sources of phosphorus in the world are phosphate rocks, which are being depleted at a rapid rate due to increased demand as a result of population growth (Cordell et al, 2009). Wastewater mismanagement and the release of phosphorus into water bodies is the primary reason for environmental degradation such as eutrophication (Udert, 2018).…”

“…This process is also beneficial as it maximizes the recoverable nutrients from urine. It has been shown to be an effective method for producing calcium phosphate on-site, within novel nutrient recovery urinals (Flanagan and Randall, 2018), and the urine-derived fertilizers are just as effective as conventional fertilizers (Meyer et al, 2018).…”