Runoff and Leachate Phosphorus and Nitrogen Losses from Grass‐Vegetated Soil Boxes Amended with Biosolids and Fertilizer

Abstract

Recent evidence suggests an upward trend in surface water phosphorus (P) concentrations in many segments of Florida, including the upper basin of the St. Johns River, a region that currently receives about two‐thirds of the state Class B biosolids land application. Concerns about water quality in this area are encouraging reexamination of the regulations governing biosolids programs. The objectives of this study were (i) to identify and thoroughly characterize the main biosolids sources routinely applied in the region, and (ii) to evaluate runoff and leachate N and P losses from a typical Florida Spodosol amended with biosolids or commercial inorganic fertilizer. Biosolids and inorganic fertilizer were surface applied uniformly at a rate equivalent to ∼114 kg P ha−1, which corresponded to a typical P load associated with nitrogen (N)‐based biosolids application. Soluble reactive P (SRP) was the predominant form of P lost in runoff and leachate. Inorganic P fertilizer increased flow‐weighted runoff total P concentrations nearly 60‐fold relative to control treatment (0.4 vs. 22 mg P L−1 for control and fertilizer treatments, respectively). With exception of biological P removal (BPR) biosolids, all other tested biosolids yielded flow‐weighted runoff P concentrations similar to untreated soils. Cumulative P and N losses (as a percentage of P and N applied) were greater from commercial inorganic fertilizer (∼38% of P and 46% of N) than any biosolids source (3% of P and 6% of N). Results demonstrate the value of water‐extractable P (WEP) as an indicator of biosolids P loss potential. Core Ideas Biosolids presented a lower risk of P and N losses than inorganic fertilizer. Nitrogen and P lability varies significantly depending on the biosolids treatment process. Data supported the usefulness of water‐extractable P as an indicator of biosolids P loss potential. More field research is warranted to understand nutrient dynamics in biosolids‐amended soils.

Biochar type and application methods affected nitrogen and phosphorus leaching from a sandy soil amended with inorganic fertilizers and biosolids

“…Most of biosolids N is present in organic forms that require mineralization before becoming bioavailable. Our results are consistent with previous studies that reported less N leaching from biosolids as compared with inorganic fertilizer (Esteller et al., 2009; Iduna et al., 2018; Lu et al., 2020; Silveira et al., 2019). For instance, in a column study, Iduna et al.…”

“…Most (>90%) of the P present in inorganic fertilizer was water‐soluble, whereas biosolids typically exhibited high levels of P‐binding constituents (Fe salts for P control) that reduce P solubility (Elliott et al., 2002). Similar results have been reported in various previous studies that there is significantly greater leaching of P from inorganic fertilizer than biosolids‐amended soil (Chinault & O'Connor, 2008; Elliott et al., 2002; Esteller et al., 2009; Silveira et al., 2019). Although previous research indicated that biosolids PSR values >1 are an indicative of greater biosolids‐P solubility and leachability (Elliott et al., 2002; Silveira et al., 2019), our results demonstrated that Class AA (PSR of 1.5) resulted in 39% less P mass leached than Class B (PSR of 1.0) material.…”

“…A major benefit of biosolids is the general slow‐release pattern of nutrients, particularly N, which can provide crops with a steady source of N supply throughout the entire growing season (Lu et al., 2020). Conversely, most nutrients in inorganic fertilizers occur primarily in readily available forms that can be subjected to off‐site transport (Lu et al., 2020; Silveira et al., 2019). Results from the current study indicated the greatest amounts of NH 4 + –N, NO 3 – –N, and total N mass leached were associated with inorganic fertilizer treatment.…”

Biochar impacts on nutrient dynamics in a subtropical grassland soil: 1. Nitrogen and phosphorus leaching

“…Spikes in leachate SRP concentrations were generally associated with inorganic fertilizer treatments, whereas biosolids treatments resulted in leachate SRP concentrations similar to control treatments. Several authors reported similar greater solubility of fertilize P vs. biosolids P (Alleoni, Brinton, & O'Connor, 2008; Silveira et al., 2019; Yang et al., 2008). Most (>90%) of the P present in inorganic fertilizer was water soluble, whereas biosolids exhibited significantly reduced water‐extractable P (0.7 to 6% of total P, Table 2), mainly due to its relatively high levels of P‐binding constituents (added Fe salts for P solubility control).…”

Biochar as Influenced by Feedstock Variability: Implications and Opportunities for Phosphorus Management

“…They speculated the P could be adsorbed on Al, Fe, or Ca, just like in soils (McDowell and Condron, 2000;Sharpley et al, 2004;Qian and Jiang, 2014). Since biosolids differ in their characterization based on their treatment processes (Freitas et al, 2017;Silveira et al, 2019), associations with P could also differ depending on the biosolids source.…”