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Phosphorus (P) is essential for all living things and an integral part of food production. However, significant amounts of P are functionally lost when wastewater byproducts, such as biosolids or sewage sludge incinerator ash (SSA), are not beneficially reused. Around 20% of sewage sludge produced in the US is incinerated and nearly 25% of sewage sludge is incinerated in European Union member countries. SSA contains significant amounts of P (up to 14% total P) and other beneficial elements but is typically sent to landfills for disposal. However, SSA has also been explored as one method of capturing and redirecting P back into the food system. Research investigating SSA characterization, P availability, and contaminant concentrations and behavior in soil is required to understand the effects of SSA land application on soil chemical properties and crop production. Several approaches for recovering P from SSA have been investigated that consider these factors. Ultimately, the opportunity for land application of SSA depends on the individual characteristics of a given SSA, ex. total P and contaminant concentrations, and the requirements and regulations of the region where it is produced and applied. In this review, we address the history of P recovery from SSA and discuss research regarding characterization, contaminants, P availability, and land application of SSA., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

Switchgrass (Panicum virgatum L.) is a native perennial grass identified as a promising biofuel crop for production on marginal agricultural lands. As such, research into switchgrass fertility and the switchgrass rhizosphere microbiome has been ongoing in an effort to increase production sustainability. We examined the effects of cultivar and phosphorus (P) fertilization on biomass yield, P removal, and rhizosphere bacterial and fungal community structure in three switchgrass cultivars: Sunburst, Shawnee, and Liberty. The Liberty cv. is the first lowland-type bioenergy switchgrass adapted to USDA hardiness zones 4, 5, and 6. On a medium soil test P clay loam soil, biomass yield response to applied P was linear, increasing 135 kg ha -1 for every kilogram of P applied prior to establishment. Average post-frost biomass yield was 9.6 Mg ha -1  year -1 when unfertilized, and maximum biomass yield was 10.3 Mg ha -1  year -1 when fertilized at 58.6 kg ha -1 P, suggesting that P application on medium soil test P soils is beneficial for switchgrass establishment and early growth. Switchgrass cv. Shawnee was more productive than cvs. Liberty or Sunburst (11.3, 10.2, and 8.6 Mg ha -1  year -1 , respectively). Both bacterial and fungal communities were significantly shaped by cultivar. These shifts, while inconsistent between year and cultivar, may reflect a selection of the microbial community from that present in soil to maximize total nutrient uptake, regardless of additional P amendments. Phosphorus fertilization did not affect microbial community structure. Results of this study suggest that the cultivar-associated selection of particular microbial taxa may have implications for increased productivity.

Phosphorus enrichment of surface water is a concern in many urban watersheds. A 3-yr study on a silt loam soil with 5% slope and high soil test P (27 mg kg(-1) Bray P1) was conducted to evaluate P fertilization and clipping management effects on P runoff from turfgrass (Poa pratensis L.) under frozen and nonfrozen conditions. Four fertilizer treatments were compared: (i) no fertilizer, (ii) nitrogen (N)+potassium (K)+0xP, (iii) N+K+1xP, and (iv) N+K+3xP. Phosphorus rates were 21.3 and 63.9 kg ha(-1) yr(-1) the first year and 7.1 and 21.3 kg ha(-1) yr(-1) the following 2 yr. Each fertilizer treatment was evaluated with clippings removed or clippings recycled back to the turf. In the first year, P runoff increased with increasing P rate and P losses were greater in runoff from frozen than nonfrozen soil. In year 2, total P runoff from the no fertilizer treatment was greater than from treatments receiving fertilizer. This was because reduced turf quality resulted in greater runoff depth from the no fertilizer treatment. In year 3, total P runoff from frozen soil and cumulative total P runoff increased with increasing P rate. Clipping management was not an important factor in any year, indicating that returning clippings does not significantly increase P runoff from turf. In the presence of N and K, P fertilization did not improve turf growth or quality in any year. Phosphorus runoff can be reduced by not applying P to high testing soils and avoiding fall applications when P is needed.

Land application of wastewater has become an important disposal option for food-processing plants operating year-round. However, there are concerns about nutrient leaching from winter wastewater application on frozen soils. In this study, P and N leaching were compared between nongrowing season application of tertiary-treated wastewater plus growing season application of partially treated wastewater (NGS) vs. growing season application of partially treated wastewater (GS) containing high levels of soil P. As required by the Minnesota Pollution Control Agency (MPCA), the wastewater applied to the NGS fields during October through March was treated such that it contained < or =6 mg L(-1) total phosphorus (TP), < or =10 mg L(-1) NO3-N, and < or =20 mg L(-1) total Kjeldahl nitrogen (TKN). The only regulation for wastewater application during the growing season (April through September) was that cumulatively it did not exceed the agronomic N requirements of the crop in any sprayfield. Application of tertiary-treated wastewater during the nongrowing season plus partially treated wastewater during the growing season did not significantly increase NO3-N leaching compared with growing season application of nonregulated wastewater. However, median TP concentration in leachate was significantly higher from the NGS (3.56 mg L(-1)) than from the GS sprayfields (0.52 mg L(-1)) or nonirrigated sites (0.52 mg L(-1)). Median TP leaching loss was also significantly higher from the NGS sprayfields (57 kg ha(-1)) than from the GS (7.4 kg ha(-1)) or control sites (6.9 kg ha(-1)). This was mainly due to higher hydraulic loading from winter wastewater application and limited or no crop P uptake during winter. Results from this study indicate that winter application of even low P potato-processing wastewater to high P soils can accelerate P leaching. We conclude that the regulation of winter wastewater application on frozen soils should be based on wastewater P concentration and permissible loading. We also recommend that winter irrigation should take soil P saturation into consideration.

Phosphorus-immobilizing amendments can be useful in minimizing P leaching from high P soils that may be irrigated with wastewater. This study tested the P-binding ability of various amendment materials in a laboratory incubation experiment and then tested the best amendment in a field setup using drainage lysimeters. The laboratory experiment involved incubating 100-g samples of soil (72 mg kg(-1) water-extractable phosphorus, WEP) with various amendments at different rates for 63 d at field moisture capacity and 25 degrees C. The amendments tested were alum [Al2SO4)3.14H2O], ferric chloride (FeCl3), calcium carbonate (CaCO3), water treatment residual (WTR), and sugarbeet lime (SBL). Ferric chloride and alum at rates of 1.5 and 3.9 g kg(-1), respectively, were the most effective amendments that decreased WEP to 20 mg kg(-1), below which leaching has previously been shown to be low. Alum (1.3 kg m(-2)), which is less sensitive to redox conditions, was subsequently tested under field conditions, where it reduced WEP concentration in the 0- to 0.15-m layer from 119 mg kg(-1) on Day 0 to 36.1 mg kg(-1) (85% decrease) on Day 41. Lysimeter breakthrough tests using tertiary-treated potato-processing wastewater (mean total phosphorus [TP] = 3.4 mg L(-1)) showed that alum application reduced leachate TP and soluble reactive phosphorus (SRP) concentrations by 27 and 25%, respectively. These results indicate that alum application may be an effective strategy to immobilize P in high P coarse-textured soils. The relatively smaller decreases in TP and SRP in the leachate compared to WEP suggest some of the P may be coming from depths below 0.2 m. Thus, to achieve higher P sequestration, deeper incorporation of the alum may be necessary.

Incinerating turkey manure is a new option in the USA to generate renewable energy and to eliminate environmental problems associated with manure stockpiling. Incineration produces turkey manure ash (TMA) with a nutrient content of 43 g phosphorus (P) kg-1 and 100 g potassium (K) kg-1. We conducted a greenhouse pot study using a low P (6 mg kg-1) and high K (121 mg kg-1) soil/sand mixture with a 7.0 pH to evaluate early growth response of corn (Zea mays L.) to TMA. A control and five rates based on P (5.6, 10.9, 16.5, 21.9, and 27.2 mg kg-1) and respective K contents in TMA were compared with triple-superphosphate and potassium chloride fertilizer. Plant height and stalk thickness at 24 and 31 days after emergence (DAE) were greatest with the fertilizer, but no differences were detected at the final sampling (52 DAE). Regardless of nutrient source, plant biomass increased with P rate. Because of faster initial plant development, corn dry matter 52 DAE was 15 to 20% greater with fertilizer than with TMA. Corn tissue P concentration was greater with TMA than with fertilizer, but P uptake was similar. Tissue micronutrient concentrations were greatest for the control. Bray 1 P appeared to extract excessive amounts of P in TMA-amended soil, whereas soil P levels with the Olsen extractant provided an estimate of plant-available P that was consistent with plant response. Based on this first approximation, we conclude that TMA is a potential source of P for field crops. Field studies are required to determine recommended application rates. [ABSTRACT FROM AUTHOR]

A power plant that utilizes turkey manure as fuel to produce energy was built in Benson, Minnesota, and started full energy production in 2007. The plant was built to meet legislative requirements governing the use of renewable sources to generate energy in Minnesota. Although the use of turkey manure as biofuel generates energy, it also results in turkey manure ash (TMA) as a by-product that contains phosphorus (P), potassium (K), sulfur (S), and zinc (Z) as well as other essential and nonessential elements. A 2-year study was conducted to compare TMA with triple-superphosphate and potassium chloride fertilizers as a source of nutrients for alfalfa (Medicago sativa) at three locations: Lamberton, Morris, and Appleton, Minnesota. The soils at Lamberton and Appleton were acidic with P and K concentrations ranging from medium-high to very high, whereas the soil at Morris was alkaline with high concentrations of P and K. The experiment consisted of a control (0 P and 0 K) and annual and split applications of TMA and fertilizer. Annual TMA and fertilizer rates were 84 kg P2O5 ha-1, 118 kg K2O ha-1, and 34 kg S ha-1. Split rates were 42/42 kg P2O5 ha-1, 59/59 kg K2O ha-1, and 17/17 kg S ha-1. However, because of an overestimation of citrate-soluble P in 2005 for the TMA, the total amount of available P applied with the TMA for the 2-year study was 168 kg P2O5 ha-1 compared with 286 kg P2O5 ha-1 for the fertilizer. In the first year, fertilizer resulted in greater alfalfa biomass yield than TMA and the control, whereas in the second year, alfalfa yields with TMA and fertilizer were similar and both more than the control. In 2005, TMA resulted in more copper (Cu) and S tissue concentrations than the fertilizer. In 2006, application of both sources increased tissue P and S concentrations compared with the control. The TMA increased tissue Cu concentration and Zn plant uptake compared with fertilizer. Bray P1-extractable soil P concentrations were less with TMA and control treatments than with the fertilizer treatments. Ammonium acetate-extractable soil sodium (Na) concentrations were greater with TMA than with fertilizer and the control. By the second year, both ash and fertilizer treatments resulted in more K uptake than the untreated control with no difference in K uptake between the two sources or time of application. Both sources were effective in increasing P uptake compared with the untreated control. TMA was shown to be an effective source of nutrients for alfalfa production. [ABSTRACT FROM AUTHOR]

‘Honeycrisp’ is a recently released cultivar of apple ( Malus x domestica ) developed by the University of Minnesota, now in high demand by growers and consumers. This cultivar is susceptible to bitter pit, especially when the trees are young and the fruit load is low. The effects of calcium (Ca) sprays, fruit thinning, vegetative growth, fruit and leaf nutrient concentration on bitter pit incidence, and two sampling methods for nutrient analysis were studied. Bitter pit incidence was associated with several variables, including Ca and phosphorus (P) concentrations in leaves and fruits, magnesium (Mg) concentration in leaves, and yield parameters. Fruit Ca concentration and content for the growing season were modeled, which allowed the determinations of Ca levels associated with bitter pit incidence. Our data suggest that plug analysis was less sensitive than fruit-segment analysis for finding differences in Ca concentrations. [ABSTRACT FROM AUTHOR]