Abstract
Industrial by-products like paper mill biosolids (PB) have been used as fertilizers and amendments in agriculture for many decades. However, their content of plant essential nutrients including phosphorus (P) varies largely with sources and availability of these nutrients once applied to soil still remains unknown. Five PB differing in their C/N ratio were used in an incubation study to assess the P forms and availability from both PB and PB-amended soils. Biosolids were added to three contrasting soils in 500-mL jars at the rate of 50 Mg wet ha-1, supplying between 36 and 113 kg total P ha-1. An unfertilized control was also included. Biosolids and soil P fractions were determined by a modified Hedley fractionation method following two and 16 weeks of incubation. Phosphorus forms in PBs varied with type of materials with labile P ranging from 20 to 72% and organic P (Po) ranging from 28 to 66% of total P. Soil incubated with PB showed changes in all P fractions due to amendment, soil types and duration of incubation. Resin-P and labile P, the most available forms, were significantly higher with addition of high PB-P content. Soil labile P represented up to 50% of total P added by PB. Overall, most inorganic P (Pi) fractions and labile P further increased with incubation duration. Close relationships were established between resin-P and labile P content in PB and the increases of those fractions in incubated soils, notably after two weeks. We concluded that some PB could be used as efficient sources of P for fertilizing crops.
Highlights
The non-renewable status of extractable phosphorus (P) on Earth (Cordell et al, 2009) has resulted in an increasing interest of alternative sources such as the use of biosolids in agriculture (Shu et al, 2016)
The N/P ratios for nutrient crop uptake in field crops varied from 4.5 to 8.7 (Sadras, 2006), which are considerably higher than those found in municipal biosolids (2.7) but much closer to paper mill biosolids (PBs) (5.7) (Miller et al, 2000; Charbonneau et al, 2001; Maguire et al, 2001)
The Kamouraska silty clay (KAM) and StA soils were selected to evaluate the response of PB in acidic soils, where P fixation occurs predominantly with Fe and Al oxides/hydroxides
Summary
The non-renewable status of extractable phosphorus (P) on Earth (Cordell et al, 2009) has resulted in an increasing interest of alternative sources such as the use of biosolids in agriculture (Shu et al, 2016). Biosolids application can positively enhance crop dry matter production and yield through their N availability. Some concerns about biosolids application, such as potential environment contamination, make its management a very important part when used in agriculture soils. Biosolids are often applied based on crop N requirements, which may lead to soil P accumulation and increase the risk of P loss to surface or groundwater (Kelling et al, 1977; Shober and Sims, 2003; Pierzynski and Gehl, 2005). Biosolids properties and their treatment plant process may have a significant impact on their fertilizer value, which can affect soil P availability (Frossard et al, 1996; Maguire et al, 2001; Penn and Sims, 2002; Torri et al, 2017)
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