Water-Extractable Phosphorus in Animal Manure and Manure Compost: Quantities, Characteristics, and Temporal Changes

The Identification of Manure Spreading on Bare Soil through the Development of Multispectral Indices from Sentinel-2 Data: The Emilia-Romagna Region (Italy) Case Study

Satellite remote sensing is currently an established, effective, and constantly used tool and methodology for monitoring agriculture and fertilisation. At the same time, in recent years, the need for the detection of livestock manure and digestate spreading on the soil is emerging, and the development of spectral indices and classification processes based on satellite multispectral data acquisitions is growing. However, the application of such indicators is still underutilised and, given the polluting impact of livestock manure and digestate on soil, groundwater, and air, an in-depth study is needed to improve the monitoring of this practice. Additionally, this paper aims at exposing a new spectral index capable of detecting the land affected by livestock manure and digestate spreading. This indicator was created by studying the spectral response of bare soil and livestock manure and digestate, using Copernicus Sentinel-2 MSI satellite acquisitions and ancillary datasets (e.g., soil moisture, precipitation, regional thematic maps). In particular, time series of multispectral satellite acquisitions and ancillary data were analysed, covering a survey period of 13 months between February 2022 and February 2023. As no previous indications on fertilisation practices are available, the proposed approach consists of investigating a broad-spectrum area, without investigations of specific test sites. A large area of approximately 236,344 hectares covering three provinces of the Emilia-Romagna Region (Italy) was therefore examined. A series of ground truth points were also collected for assessing accuracy by filling in the confusion matrix. Based on the definition of the spectral index, a value of the latter greater than three provides the most conservative threshold for detecting livestock manure and digestate spreading with an accuracy of 62.53%. Such results are robust to variations in the spectral response of the soil. On the basis of these very encouraging results, it is considered plausible that the proposed index could improve the techniques for detecting the spreading of livestock manure and digestate on bare ground, classifying the areas themselves with a notable saving of energy compared to the current investigation methodologies directly on the ground.

Twenty years of catchment monitoring highlights the predominant role of long-term phosphorus balances and soil phosphorus status in affecting phosphorus loss in livestock-intensive regions

Livestock husbandry has raised enormous environmental concerns around the world, including water quality issues. Yet there is a need to document long-term water quality trends in livestock-intensive regions and reveal the drivers for the trends based on detailed catchment monitoring. Here, we assessed the concentration and load trends of dissolved reactive phosphorus (DRP) in streamwater of a livestock-intensive catchment in southwestern Norway, based on continuous flow measurements and flow-proportional composite water sampling. Precipitation and catchment-level soil P balance were monitored to examine the drivers. At the field level, moreover, the relationship between soil P balance and soil test P (measured using the ammonium lactate extraction method, P-AL) was assessed. Results showed that on average of 20 years 95 % of the P was applied to the catchment during March-August, when 40 % of annual precipitation and 25 % of annual discharge occurred. The low runoff helped reduce P loss following P applications. However, flow-weighted annual mean DRP concentration significantly increased with increasingly cumulative soil P surplus (R2 = 0.55, p = 0.0002). With a mean annual P surplus of 8.8 kg ha-1, the annual mean DRP concentration (range: 49-140 μg L-1; mean: 80 μg L-1) and annual DRP load (range: 0.35-1.46 kg ha-1; mean: 0.65 kg ha-1) significantly increased over the 20-year monitoring period (p = 0.001 and 0.0003, respectively). At the field level, P-AL concentrations were positively correlated with soil P balances (R2 = 0.48, p < 0.0001), confirming the long-term impact of P balances on the risks of P loss. The study highlights the predominant role of long-term P balances in affecting DRP loss in livestock-intensive regions through the effect on soil test P.

The role of microbiota during chicken manure and pig manure co-composting

Co-composting is an excellent and effective technology for treating livestock manure in which microorganisms play a crucial function. Therefore, this study aimed at investigating the changes of microbial interactions during co-composting. Six different addition ratios of chicken and pig manure were used in composting experiment. The results showed that the co-composting system using 60% chicken manure and 40% pig manure significantly altered the microbial diversity and community structure. In addition, the complexity and tightness of its microbial community network structure reached the maximum, as did the strength of its cooperative and competitive microbial interactions. The higher microbial abundance and microbial interaction have the potential to promote the decomposition and transformation of compost components. Therefore, this study preliminarily revealed the changes of microbial community in co-composting, which provided a theoretical basis for optimizing microbial community interaction in composting systems by mixing different ratios of materials in practice.

Phosphorus characteristics of Canada-wide animal manures and implications for sustainable manure management with a cleaner environment

Animal manure can be a serious environmental concern if improperly managed, particularly with regard to phosphorus (P). A good understanding on manure P chemistry is required for improving manure management in an environmentally sustainable manner. In the study, 102 representative manure samples collected from farms of major intensive livestock areas of Canada were sequentially fractionated with H₂O, 0.5 M NaHCO₃, 0.1 M NaOH, and 1.0 M HCl, respectively, for measuring inorganic (Pi) and organic P (Po). Across the manures, total P (TP) ranged from 3.71 to 17.3 g kg^-1, with total Pi and available P (i.e., the sum of H₂O-Pi and NaHCO₃-Pi) accounting for 67.0-92.4 % and 35.6-67.3 % of TP, respectively. Composting reduced the percentages of available P and Po in TP, and meanwhile increased the percentages of moderately stable HCl-Pi. Compared to other P fractions, manure available P increased more rapidly with increases in TP; once manure TP reached 7.8-9.6 g kg^-1, further TP increase enhanced transformation to more recalcitrant P (i.e., NaOH-Pi and HCl-Pi). Under Canadian conditions, manure application to meet the demand of crops for N would lead to P buildup in the soil at rates of 6.1-41.6 kg P ha^-1 yr^-1, increasing runoff P loss risk. Manure compost and poultry manure tend to cause rapid P buildup in the soil after land application and become a long-term P source for runoff losses. The results help to develop scientifically-sound manure-specific P management technologies which would enable farmers to achieve sustainable crop production with improved environment.

Envisioning the manureshed: Toward comprehensive integration of modern crop and animal production

The specialization and intensification of agriculture have produced incredible gains in productivity, quality, and availability of agricultural commodities but have resulted in the separation of crop and animal production. A by-product of this separation has been the accumulation of manure regions where animal production is concentrated. Enter the "manureshed," an organizing framework for integrating animal and crop production where budgeting of manure nutrients is used to strategically guide their recycling and reuse in agricultural production systems where manure resources are of highest value. To move beyond regional nutrient balance analyses into the transformational realm required to mitigate "wicked" manure problems, manureshed management requires recognition of the challenges to systematically reorganizing resource flows. In better integrating crop and livestock systems, manureshed management must account for the unique nature of managing manure nutrients within individual livestock industries, anticipate trade-offs in substituting manure for commercial fertilizer, promote technologies to refine manure, and engage extensive social networks across scales that range from the farmgate to nation and beyond.

Effects of different conditions tested "in vitro" on the phosphorus runoff potential of livestock manure

This study aimed to investigate the changes of swine and dairy manure characteristics during a long-term storage (150-180 days) under 4 °C, 20 °C, and 37 °C, sealed and unsealed conditions. Water extractable phosphorus (WEP) of both manures rapidly increased during the first 15-30 days and then decreased. At the end of the storage, the WEP reduction was 90%±3% and 71%±5% of the initial concentration for swine manure and dairy manure, respectively. Generally, unsealed storage and higher temperatures led to more WEP reduction. This study suggested that manure stored for less than 30 days had the highest P runoff potential, while a long-term manure storage reduced P runoff potential compared to freshly excreted manure.

Conditioning of Feed Material Prior to Feeding: Approaches for a Sustainable Phosphorus Utilization

A circular phosphorus (P) bioeconomy is not only worthwhile for conserving limited mineral P reservoirs, but also for minimizing negative environmental impacts caused by human-made alterations. Although P is an essential nutrient, most of the P in concentrates based on cereals, legumes and oilseed byproducts is organically bound to phytate. The latter cannot be efficiently utilized by monogastric animals and is therefore diluted into the environment through the manure pathway. This review examines various strategies for improved P utilization in animals and reflects the respective limitations. The strategies considered include feeding of debranned feedstuffs, pre-germinated feed, co-feeding of phytase and feeding material with high native phytase activity. All these approaches contribute to an improved P bioavailability. However, about half of the organic P content continues to be excreted and therefore remains unused by the animals. Nevertheless, technologies for an efficient utilization of P from cereal-based feed already exist; however, these are not industrially established. Conditioning feed material prior to feeding fosters P-reduced feed; meanwhile, P bound to phytate can be recovered. Based on known techniques for P separation and solubilisation from cereal products and phytate conversion, potential designs for feed material conditioning processes are proposed and evaluated.

Enhanced phosphorus mobility in a calcareous soil with organic amendments additions: Insights from a long term study with equal phosphorus input

The agricultural practice of replacing chemical fertilizers with organic amendments (manure and/or straw) may have consequences for phosphorus (P) loss to the environment. Such a knowledge gap was examined using a ten-year field trial in calcareous soil containing four treatments with the equal annual P input but varied organic amendment combinations as follows: mineral fertilizer only as control (MF), mineral fertilizer coupled with manure (MM), mineral fertilizer coupled with manure and straw (MMS) and mineral fertilizer coupled with straw (MS). The soil P distribution, P fractions and speciation, Fe(III) reduction and P sorption kinetics were investigated using the chemical extraction, K edge X-ray absorption near-edge structure and Langmuir equations. The electronic shuttle capacity of soils and speciation of soil dissolved organic matter (DOM) were also evaluated using electrochemical methods, three-dimensional excitation-emission matrix fluorescence spectroscopy and Fourier transform infrared spectra methods. Results showed that soil Olsen-P and total P increased at depths of 20-40 cm in MM, MMS and MS treatments, suggesting that manure and/or straw addition significantly mobilized P in the soil profile. Manure and/or straw addition also decreased soil maximum P sorption capacity (S_max) and increased the desorption rate at depths of 0-20 cm in soil across treatments. At a depth of 0-20 cm in soil of the MS treatment, the enhanced Fe(Ⅲ) reduction coupled with a decrease of Fe-bound P supports that Fe reduction dominates the mobilization of P. The transformation of Ca bound-P to Al/Fe bound-P in a depth of 0-20 cm in soil of the MM treatment may be due to the high proportion of humic-like substances in the DOM at a depth of 0-20 cm in soil of the MM treatment, which may have caused a slight/microsite acidification. These results can help to develop optimized fertilization practices to effectively mitigate P loss from calcareous soils with manure and/or straw addition.

The Chesapeake Bay Program Modeling System: Overview and Recommendations for Future Development

The Chesapeake Bay is the largest, most productive, and most biologically diverse estuary in the continental United States providing crucial habitat and natural resources for culturally and economically important species. Pressures from human population growth and associated development and agricultural intensification have led to excessive nutrient and sediment inputs entering the Bay, negatively affecting the health of the Bay ecosystem and the economic services it provides. The Chesapeake Bay Program (CBP) is a unique program formally created in 1983 as a multi-stakeholder partnership to guide and foster restoration of the Chesapeake Bay and its watershed. Since its inception, the CBP Partnership has been developing, updating, and applying a complex linked modeling system of watershed, airshed, and estuary models as a planning tool to inform strategic management decisions and Bay restoration efforts. This paper provides a description of the 2017 CBP Modeling System and the higher trophic level models developed by the NOAA Chesapeake Bay Office, along with specific recommendations that emerged from a 2018 workshop designed to inform future model development. Recommendations highlight the need for simulation of watershed inputs, conditions, processes, and practices at higher resolution to provide improved information to guide local nutrient and sediment management plans. More explicit and extensive modeling of connectivity between watershed landforms and estuary sub-areas, estuarine hydrodynamics, watershed and estuarine water quality, the estuarine-watershed socioecological system, and living resources will be important to broaden and improve characterization of responses to targeted nutrient and sediment load reductions. Finally, the value and importance of maintaining effective collaborations among jurisdictional managers, scientists, modelers, support staff, and stakeholder communities is emphasized. An open collaborative and transparent process has been a key element of successes to date and is vitally important as the CBP Partnership moves forward with modeling system improvements that help stakeholders evolve new knowledge, improve management strategies, and better communicate outcomes.

Effects of the origins and stabilization of biosolids and biowastes on their phosphorous composition and extractability

Phosphorous dissolution and ensuing chemical redistribution of P in organic amendments (OA) were studied by applying a modified Hedley selective fractionation to eight water-extracted and unextracted OAs. Nine 7-day, repeated extractions were applied using a 60:1 water:dry OA (v:w) ratio at pH 8. Eight OAs were tested including five biosolids, broiler litter, dairy manure compost and municipal solid waste compost. The average PWEP₉ (percent water-extractable P following nine water-extraction cycles) for the OAs was 65 ± 9% and all of the fractions, with almost no exceptions, contributed to that figure. Organic P was depleted by mineralization (in non-stabilized sludges and broiler litter) or dissolution (stabilized composts) or both (in lime-treated biosolids) and that depletion was completed within 1-2 extraction cycles. Only the organic P of the MSWC remained undepleted. Strong linear correlations were observed between the WEP₉ values of the OAs (0.8-21 g P kg^-1) and several more easily determined properties, including total P content (r² = 0.84), organic N content (r² = 0.82), the sum of Hedley's more easily dissolved SRP (soluble reactive P) and OP (r² = 0.95), and the total P and SRP extracted by 16 h of shaking with the bicarbonate reagent (r² ≥ 0.90). These findings indicate that if greater P availability is desired, the stabilization of biosolids and biowastes should be minimized. These insights into the relationships between OA characteristics and P solubility may benefit the use of OAs in agricultural systems and aid assessments of the environmental significance of their use.

Effects of temperature and inoculation ratio on methane production and nutrient solubility of swine manure anaerobic digestion

This study investigated the effects of temperature and volatile solids (VS) ratio of feedstock to inoculum (F/I ratio) on methane (CH₄) production and the solubility of nitrogen (N), phosphorus (P), cooper (Cu), and Zinc (Zn) after anaerobic digestion (AD) of swine manure. The highest cumulative CH₄ yield of 470 L/kgVS_feed was obtained with F/I ratios of 2.0 and 3.0 with mesophilic (37 °C) temperature, and methane production rate decreased with the increase of F/I ratio. As F/I ratio increased from 0.5 to 4.0, the lag phase for methane production increased from 1.02 days to 13.52 days, indicating an initial inhibition at high F/I ratios. AD increased the concentrations of ammonia, Cu and Zn in the AD effluent supernatant, while decreased total and water extractive P concentrations. The changes of ammonia, Cu, Zn, and P concentrations were more significant with the increase of F/I ratio.

Elemental Composition of Swine Manure from 1997 to 2017: Changes Relevant to Environmental Consequences

There have been revisions in the composition of swine diets in the last two decades that not only improved production profitability but also had potential environmental benefits. Among other changes, the use of phytase in feed has enabled lower total P concentrations. Nitrogen, specifically protein, concentrations are expected to be lower, and certain trace elements were also expected to change. In this study, analyses of 1195 swine slurry manure samples from various barn types in Manitoba, Canada, collected from 1997 to 2002 were compared with similar analyses from 2010 and 2017. Concentrations of P were significantly lower in 2017, from a median in sow barns of 28.0 g kg dry weight (dw) in 1998 to 2002 to 20.6 g kg dw in 2010 and 2017, and from a median in feeder finisher barns of 24.1 g kg dw in 1998 to 2002 to 18.7 g kg dw in 2010 and 2017. Total N levels did not change with time, but the fraction of manure N that was NH decreased. Zinc concentrations were consistently higher in nursery manures than in other swine manures and increased from a median of 2800 mg kg dw in nursery barns in 1998 to 2002 to 5580 mg kg dw in nursery barns in 2010 and 2017. Concentrations of most other trace elements decreased over this time period. With the exception of Zn from nursery barns, these temporal changes should lessen the potential for environmental consequences from swine manure application to land.