Effectiveness of recycled P products as P fertilizers, as evaluated in pot experiments

Abstract

World phosphorus (P) resources are limited and may be exhausted within 70-175 years. Therefore recycling of P from waste materials by chemical or thermal processes is important. This study evaluated the effectiveness of recycled P products from sewage sludge and animal wastes as P fertilizer. Four products were obtained from chemical processes, three magnesium-ammoniumphosphates (MAP) of different sewage treatment plants and a Ca phosphate precipitated from wastewater (Ca-P) and four from thermal processes, an alkali sinter phosphate (Sinter-P), a heavy metal depleted sewage sludge ash (Sl-ash), a cupola furnace slag made from sewage sludge (Cupola slag) and a meat-and-bone meal ash (MB meal ash). The effectiveness of these products as P fertilizers compared with triple superphosphate (TSP) and phosphate rock (PR) was determined in a 2-year pot experiment with maize (Zea mays L., cv. Atletico) in two soils with contrasting pH (pH(CaCl 2 ) 4.7 and 6.6). The parameters used to evaluate the effectiveness were P uptake, P concentration in soil solution (C Li ) and isotopically exchangeable P (IEP). MAP products were as effective as TSP in both soils, while Ca-P was only effective in the acid soil. Sinter-P was as effective as TSP in the acid soil, while Cupola slag was in the neutral soil. The products Sl-ash and MB meal ash were of low effectiveness and were comparable to PR. The effect of the fertilizers on IEP, but not on C Li , described their effectiveness. Recycled P products obtained by chemical processes, especially MAP, could be directly applied as P fertilizers, while products such as Sl-ash and MB meal ash are potential raw materials for P fertilizer production.Keywords Phosphorus recycled products Á P fertilizer efficiency Á Isotopically exchangeable P Á P in soil solution Á Struvite Á Ash Á Slag Á Soil reaction Abbreviations P-0 Unfertilized TSP-60 Triple superphosphate (60 mg P kg -1 ) TSP-200 Triple superphosphate (200 mg P kg -1 ) PR Phosphate rock Ca-P Calcium phosphate MAP-Sb Magnesium-ammonium-phosphate (MAP) Seaborne

Can Phosphate Salts Recovered from Manure Replace Conventional Phosphate Fertilizer?

“…Previous studies comparing P fertilizers/struvites recovered from various materials to commercial P fertilizer have reported that the recycled products increased DMY in maize [20], led to comparable DMY in perennial ryegrass [22], or at least improved DMY compared to untreated controls in several crops [17][18][19]43].…”

“…Several studies have found that struvite recovered from different materials can improve the yields of various crops compared to untreated controls [17][18][19]. Struvite recovered from swine wastewater has been shown to increase the biomass yield of maize more than commercial P fertilizer [20].…”

“…Johnston and Richards [22] as well as Römer [23] confirmed that some P fertilizers ensure relatively good P availability and supply despite the small amounts contained in water-soluble form. Cabeza et al [17] concluded that the dissolution of P in soil is a much more accurate indicator of the fertilizing effectiveness of recycled P products than their solubility in water or citric acid. Thus, plant experiments are crucial to evaluate the actual efficacy of the P-Salt in terms of P-fertilizing performance.…”

Influence of Soil and Irrigation Water pH on the Availability of Phosphorus in Struvite Derived from Urine through a Greenhouse Pot Experiment

“…Several previous investigations have also suggested that struvite may be an effective fertilizer for acidic soil. 8,20 Massey et al 10 conducted a greenhouse study with struvite and other P fertilizers at different soil pH levels and reported that struvite was effective at both acidic and slightly alkaline pH levels. However, it was found in our study that struvite in cinnamon soil (pH 7.3) had lower performance on biomass compared to CSP treatment, but not significantly, but showed significantly higher level in biomass in paddy soil (pH 5.3).…”

“…It is known that water-soluble P fertilizer is generally considered to be fully plant available, and the P uptake from struvite has been studied in the greenhouse with a variety of test plants on soils compared with commercial P fertilizer. [8][9][10][11] evaluated the availability of urine-derived struvite as fertilizer and found that struvite led to biomass yield and P uptake comparable to or higher than those induced by a commercial mineral fertilizer. A few reports of the comparison of soils with different pH values can be found in previous research.…”