Estimation of phosphorus bioavailability from composted organic wastes

Influence of Different Rates of Plant-Based Compost on Clay Soil Metal Behavior and Human Health Risk Assessment in Moringa oleifera Leaf Biomass

An investigation of the impact of adding plant-based organic compost to clay soil from a Moringa oleifera farm focusing on the metal content, bioavailability, and accumulation of nutrients in M. oleifera leaves was conducted. Clay soil was mixed with 15%, 30%, 45% and 60% plant-based organic compost (by volume) in 20 cm wide, 2 L pots. Moringa oleifera plants were planted in four replicates of each treatment and control group. Results revealed that the addition of compost significantly (P < 0.05) altered the concentration of metals in the soil. Correspondingly, accumulation of nutrients in M. oleifera leaves increased with the addition of compost to the soil, except for cobalt and chromium. Trace elements had minimal bioavailability in the amended soils, and their presence in the leaves was lower than the permissible trace metal levels in food. The 30% combination had the highest concentration of calcium (45 042.5 mg/kg), magnesium (17430.0 mg/kg) and phosphorous (8802. 5 mg/kg) in M. oleifera leaves. The study concluded the addition of compost improved bioavailability of nutrients in the soil and their concentration in M. oleifera leaves. The target hazard quotients for heavy metals was less than one, indicating that M. oleifera leaf biomass harvested from soil amended with plant-based compost is safe for human consumption. These results serve as guidelines for recommended organic certification requiremets where plant-based compost is often used in the fast-growing herbal industry.

Muz Atıkları Kompostunun Toprağın Azot ve Fosfor ile İlişkili Enzimatik Aktiviteleri Üzerine Kısa Süreli Etkisinin İzlenmesi

A large amount of plant pruning waste occurs after annual care in banana production areas. This waste material contains significant amounts of organic substances and nutrients. In this study, banana waste compost (BWC) was applied to the soil both alone and in mixture with leonardite (LT) and vinasse compost (VC). Treatments include: control (CL), banana waste compost alone (BWC-2: 2 t da-1; BWC-4: 4 t da-1; BWC-8: 8 t da-1), leonardite alone (LT: the recommended application rate), leonardite with banana waste compost (BWC-2+LT; BWC-4+LT; BWC-8+LT), vinasse compost alone (VC: the recommended application rate), vinasse compost with banana waste compost (BWC-2+VC; BWC-4+VC; BWC-8+VC). Afterwards, the changes in the activities of nitrogen (NH4+NO3) and phosphorus (available P) related enzymes (urease and alkaline phosphatase) were monitored through analyzes made on soil samples taken on certain days (0th, 10th, 20th, 40th, 80th). During this period, the pH and EC values of the soil were also measured. According to the results obtained; it was determined that banana waste compost combined with leonardite generally positively affects the pH, EC, exchangeable NH4-NO3 and, available P of the soil, as well as the activity of urease and alkaline phosphatase compared to other treatments. In this regard, according to the control, the urease activity of the soil increased by 875%, the alkaline phosphatase activity by 149%, the exchangeable NH4+NO3 by 188%, available P by 83%, and the EC value by 100%. However, the pH value decreased by about 5%. As a result, it can be stated that the application of banana waste compost combined with leonardite as a soil conditioner at least 4 t da-1 will be economical and 10 to 20 days after this application, nitrogen and phosphorus availability will increase in the soil.

Towards sustainability: Threat of water quality degradation and eutrophication in Usangu agro-ecosystem Tanzania

The agrochemicals and nutrient losses from farming areas such as paddy farming significantly dictate quality and eutrophication of the freshwater resource. However, how farming and land use pattern affect water qualities and eutrophication remain poorly understood in most African agro-ecosystems. The present study characterized how paddy farming influences water qualities and eutrophication in 10 irrigation schemes in Usangu agro-ecosystem (UA). About 42 water samples were sampled from intakes, channels, paddy fields, and drainages and analyzed for EC, Cl, P, NH₄-N, NO₃-N, TN, Zn, Cu, Ca, and Mg. We observed water pH ranging from 4.89 to 6.76, which was generally below the acceptable range (6.5-8.4) for irrigation water. NH₄-N concentration was in a range of 10.6-70.0 mg/L, NO₃-N (8.4-33.9 mg/L), and TN (19.1-21,104 mg/L). NH₄-N increased along sampling transect (sampling points) from intakes (5.7-29.1 mg/L), channels (19-20 mg/L), fields (12.9-35.8 mg/L), and outflow (10.6-70.0 mg/L), the same trend were found for NO₃-N and TN. The TP determined in water samples were in the range of 0.01 to 1.65 mg/L; where some sites had P > 0.1 mg/L exceeding the allowable P concentration in freshwater resource, thus indicating P enrichment and eutrophication status. The P concentration was observed to increase from intake through paddy fields to drainages, where high P was determined in drainages (0.02-1.65 mg/L) and fields (0.0-0.54 mg/L) compared to channels (0.01-0.13 mg/L) and intakes (0.01-0.04 mg/L). Furthermore, we determined appreciable amount of potentially toxic elements (PTEs) such as Cu, Pb, Cd and Cr in studied water samples. The high N, P, and PTEs in drainages indicate enrichment from agricultural fields leading to water quality degradation and contaminations (eutrophication). The study demonstrates that water quality in UA is degrading potentially due to paddy rice farming and other associated activities in the landscape. Thus, the current study recommends starting initiatives to monitor irrigation water quality in UA for better crop productivity, and improved quality of drainage re-entering downstream through the introduction of mandatory riparian buffer, revising irrigation practices, to include good agronomic practices (GAP) to ensure water quality and sustainability.

Improving the humification and phosphorus flow during swine manure composting: A trial for enhancing the beneficial applications of hazardous biowastes

Improving the recovery of organic matter and phosphorus (P) from hazardous biowastes such as swine manure using acidic substrates (ASs) in conjunction with aerobic composting is of great interest. This work aimed to investigate the effects of ASs on the humification and/or P migration as well as on microbial succession during the swine manure composting, employing multivariate and multiscale approaches. Adding ASs, derived from wood vinegar and humic acid, increased the degree of humification and thermal stability of the compost. The ³¹P nuclear magnetic resonance spectroscopy and X-ray absorption near-edge structure analyses demonstrated compost P was in the form of struvite crystals, Ca/Al-P phases, and Poly-P (all inorganic P species) as well as inositol hexakisphosphate and Mono-P (organophosphorus species). However, the efficiency of P recovery could be improved by generating more struvite by adding the ASs. The flows among nutrient pools resulted from the diversity in the dominant microbial communities in different composting phases after introducing the ASs and appearance of Bacillus spp. in all phases. These results demonstrate the potential value of ASs for regulating and/or improving nutrients flow during the composting of hazardous biowastes for producing higher quality compost, which may maximize their beneficial benefits and applications.

Effects of microorganism-mediated inoculants on humification processes and phosphorus dynamics during the aerobic composting of swine manure

There is significant interest in the treatment of swine manure, which is a hazardous biowaste and a source of pathogenic contamination. This work investigated the effects of microorganism-mediated inoculants (MMIs) on nutrient flows related to humification or phosphorus (P) dynamics during the aerobic composting of swine manure. The impact of MMIs on microbe succession was also evaluated. The addition of MMIs had positive effects associated with nutrient flows, including thermal activation, decreases in certain fluorescence emissions, lower mass loss and variations in levels of certain elements and functional groups. MMIs altered the maturation behavior and kinetics of organic matter while improving microbial activity. Phosphorus was found in the compost in the forms of MgNH₄PO₄·6H₂O crystals and Poly-P as the IP species, and Mono-P as the OP species in compost generated from the dissolution or inter-transformation among P pools. These nutrient flows are attributed to changes in the structure of microbial communities as a consequence of introducing MMIs. Diverse microbial compositions were identified in different composting phases, although Bacillus appeared in each phase. This work provides support for the aerobic composting of hazardous biowaste as well as an improved understanding of nutrient flows, as a means of producing higher quality compost.

Alcaligenes aquatilis GTE53: Phosphate solubilising and bioremediation bacterium isolated from new biotope "phosphate sludge enriched-compost"

The isolation and identification of beneficial bacteria from the active phase of composting is considered to be a key bio-quality parameter for the assessment of the process. The aim of this work was the selection and identification of beneficial bacteria from a co-composting experiment of vegetable waste (VW), olive oil mill waste (O₂MW), and phosphate sludge (PS). Phosphate-solubilizing strains were isolated from the thermophilic phase using Pikovskaya (PVK) solid medium supplemented with tricalcium phosphate Ca3(PO4) (TCP) as the sole source of phosphorus (P). Therefore, the selected isolate Alcaligenes aquatilis GTE53 was tested to tolerate abiotic stresses (different levels of temperature, variable pH, high salinity and water stress). The isolate was also assessed for indole acetic acid (IAA) and siderophores synthesis, nitrogen fixation, phenol degradation and pathogens inactivation. The quality of the co-composting process was also investigated by monitoring the physico-chemical parameters. The obtained results showed that A. aquatilis GTE53 displayed a higher solubilization index of 2.4 and was efficiently dissolved, up to 162.8 and 247.4 mg·mL^-1 of inorganic phosphate from PS and phosphate rock (PR), respectively. A. aquatilis GTE53 exhibited siderophores and IAA release, along with atmospheric nitrogen fixation. In addition to that, A. aquatilis GTE53 showed a high resistance to heat and tolerance to acidic and alkaline pH, high salinity and water stress. Moreover, A. aquatilis GTE53 could degrade 99.2% of phenol from a high-concentrated medium (1100 mg·L^-1 of phenol) and can inactivate the most abundant pathogens in industrial wastes: Escherichia coli, Streptococcus sp., Salmonella sp., and Fusarium oxysporum albedinis. Analysis of temperature, pH, electrical conductivity, carbon/nitrogen (C/N) ratio, indicated successful co-composting. An efficient transformation of P to the available form and a great abatement of polyphenols, were also recorded during the process. The findings of this study will help to advance the understanding of A. aquatilis GTE53 functions and will facilitate its application to promote beneficial microbial organisms during composting, thus obtaining a high-quality product.

Evaluation of rotary drum composting for the management of invasive weed Mikania micrantha Kunth and its toxicity assessment

Mikania micrantha Kunth is an abhorrent weed that destroys agricultural output. It contains toxic compounds that are detrimental to the natural ecosystem and have negative impacts on the economic and aesthetic aspects of the environment. This study depicts the treatment and management of this plant by in-vessel composting using a 550 L rotary drum composter. Six different mix proportions of biomass, cow dung, and sawdust were used for the study. Rotary drum (RD2) with 2.71% has the highest Total Kjeldahl Nitrogen (TKN). Total Organic Carbon (TOC) decreased to 19.72% at the end of the 20th day. Final C/N ratio falls between 7 and 14 in all the reactors. The phytotoxicity test of Mikania was evaluated using Vigna radiata and Allium cepa. The findings of the study suggest that Mikania can be efficiently utilised to produce mature and stable compost that might be recommended for field application as the process can reduce toxicity.

Phosphorus fractions in soil fertilised with organic waste

The aim of this study has been to evaluate the effect of sewage sludge and composted sewage sludge and municipal waste on the content of various forms of P in soil. The experiment scheme: C, control; NPK; FYM; DGSS, dried and granulated sewage sludge; CSS, composed sewage sludge; CSSS, composted sewage sludge and straw; CMMW, composted mixed municipal waste; CMGW, composted municipal green waste. The content of bound P was determined in the fractions: F1, easily soluble; F2, exchangeable; F3, organic; F4, carbonate; F5, stable organic-mineral and mineral bonds; and F6, residual. The NPK fertilisation as well as the soil fertilisation with organic substances raised the P-total content and of P bound in the fractions: F3, F4, F5 and F6. The highest amount of phosphorus in the studied soil was in fraction F3 (phosphorus in organic compounds) and the lowest in fraction F1 (phosphorus in the ionic form as H₂PO₄^- and HPO₄^2-). Composted sludge and straw introduced into the soil increased the content of readily soluble P (F1), while the NPK effect was reversed. NPK fertilisation and enhancement of soil organic matter (except CSSS, CMGW) led to a reduction of the P content in F2 fraction. The content of available P determined by the Egner-Riehm method depended on the content of C-organic, P-total and CEC soil. Among the determined phosphorus fractions, the content of available P was most strongly correlated with the content of P bound in the carbonate fraction (F4) and residual fraction (F6) and, less strongly, with the organic phosphorus fraction.

Diversity of arthropods on Acacia mangium (Fabaceae) and production of this plant with dehydrated sewage sludge in degraded area

Sewage sludge is an organic matter-rich material with abundant fractions of nitrogen and other macro and micronutrients, essential for plant growth and development such as Acacia mangium Willd. (Fabales: Fabaceae) used in recovering actions of degraded areas. The objective of this study was to evaluate over 24 months the abundance and diversity of chewing and pollinator insects and arthropod predators on A. mangium plants and the mass production and soil coverage by this plant, fertilized with dehydrated sewage sludge, in a degraded area. The experimental design was in randomized blocks with two treatments (with and without dehydrated sewage sludge) and 24 replications. The number of leaves per branch and branches per plant, defoliation percentage by chewing insects, soil cover and abundance of chewing and pollinator insects and arthropod predators were higher on A. mangium plants fertilized with dehydrated sewage sludge. Nasutitermes sp. (Blattodea: Termitidae) and Trigona spinipes F. (Hymenoptera: Apidae) were the most observed insects on trunks and leaves, respectively, of A. mangium plants fertilized with dehydrated sewage sludge. The A. mangium fertilization increases the populations of different insect and spider groups on this plant.

Feasibility of sewage sludge derived hydrochars for agricultural application: Nutrients (N, P, K) and potentially toxic elements (Zn, Cu, Pb, Ni, Cd)

Hydrochars derived from municipal sewage sludge was analyzed for its feasibility for value-added recycling. Results of carbon content and elemental composition suggested that the hydrochars might not be comparable with pyrochars regarding to the carbon sequestration, long-term stability and fuel quality. Application as soil amendment would be a better approach for hydrochar utilization. To examine the potential benefits and risks of that, the total and available content of nutrients (i.e. N, P, and K) were measured, and the potentially toxic elements (PTEs, i.e. Zn, Cu, Pb, Ni and Cd) were analyzed for the total content, speciation, and leaching potential. Compared with pyrochars derived from the same feedstock, hydrochars had lower pH and higher cation exchange capacity. The available content of N (1.58-6.87 g/kg), P (0.270-0.901 g/kg), and K (0-0.873 g/kg) in the chars was less than the feedstock sludge (3.33 g/kg N, 3.02 g/kg P, 2.07 g/kg K), but still far higher than that of the agricultural soil (i.e. 0.014-0.488 g/kg N, 0.02 g/kg P, <0.1-0.272 g/kg). Remarkably, hydrochars showed better nutritional balance than pyrochars for its higher available K content. Risk of potentially toxic elements contamination by the sludge was efficiently reduced in either hydrochars or pyrochars, except the high leaching potential of Zn in pyrochars. Overall, in addition to the advantages of the hydrothermal carbonization process as energy saving and value-added liquid by-products, the hydrochars derived from sludge, with sufficient and balanced nutrients and limited PTEs pollution risk, can be a feasible and value-added material as soil amendment.

Response of Microbial Activities in Soil to Various Organic and Mineral Amendments as an Indicator of Soil Quality

The presented paper deals with the analysis of potential differences between organic waste compost (CBD), vermicompost (CVER) and mineral fertilizer (MF; 27% of N) applications affecting the quality of arable soil by influencing microbial activity therein. The selected types of compost represent alternatives to conventional organic fertilizers, which are, however, not available to Czech and Slovak farmers in sufficient amounts. Their mutual comparison and the comparison with organic fertilizers aim to provide farmers further information about their influence on arable land and thus to give them the possibility of deciding on the most suitable amendments. To demonstrate the effect of these amendments, six variants were prepared: one without the addition of fertilizers; two variants with the addition of 40 Mg/ha of CVER and CBD; one variant with the addition of double dosed CVER (80 Mg/ha), and the remaining two variants were fertilized only with MF (0.22 Mg/ha) and with the combination of CVER (0.20 Mg/ha) and MF (0.11 Mg/ha). Substrate induced respiration (SIR), basal respiration (BS), microbial carbon (Cmic) and enzymatic activities (hydrolysis of fluorescein diacetate—FDA, dehydrogenase activity—DHA, and phosphatase activity—PA) were used to evaluate the effect of CBD, CVER and MF application on the soil quality. Both organic and mineral amendments affected BS and SIR. The highest BS and SIR rates were found in variants with compost application (CVER and CBD). All variants treated with the mineral fertilizer showed the lowest level of enzyme activities; lower by about 30% in comparison with variants where CVER, CBD and the combination of MF and CVER were applied. We found insignificant differences between the individual types of compost. More importantly, we compared the situation at the beginning of the experiment and after its end. It was found that the application of mineral fertilizers automatically led to the deterioration of all enzymatic parameters, on average by more than 25%, as compared with the situation at the beginning of the experiment. However, when the mineral fertilizer dose was supplemented with organic amendments (CVER), this negative effect was eliminated or significantly reduced. Furthermore, both composts (CVER and CBD) positively affected plant biomass production, which reached a level of production enhanced by the MF. Results clearly showed that the application of both compost types could be used to improve soil quality in agriculture.

Current and residual phosphorous availability from compost in a ryegrass pot test

Compost can provide nitrogen (N) and especially phosphorous (P) available for plant growth, thus representing a potential alternative to chemical P-fertilizers a non-renewable resource. However, little is known about their residual capacity to provide plant-available P. In this study four compost: a green waste compost (GWC), one from anaerobically-digested bio-waste (DC), one from sewage sludge (SSC), and one from bio-waste (BWC), were compared (10 and 20 Mg VS ha^-1) in a ryegrass pot test (112 days), for their N- and P-relative mineral fertilizer equivalence (MFE; %) vs. a chemical fertilizer (NPK). After the test period, the exploited treatments were tested for their MFE during an additional ryegrass growth cycle (112 days) in an N-rich environment (N+). After 112 days, the pot test showed that DC and SSC produced dry biomass in the same range as did NPK, attaining the best N-MFE (80-100%) and P-MFE (100-125%), whereas GWC and BWC performed poorly (60-80 and 80-90%; N-MFE and P-MFE). At the end of the first growth cycle, DC and SSC still showed relevant Olsen-P (20-30 mg kg^-1). This was reflected in the best ryegrass P-MFE in DC and SSC at the end of the second growth cycle (N+), after 224 days (100-110%), whereas BWC and GWC poorly performed (90-95%). DC and SSC may therefore represent valuable sources of N available for plant nutrition in the short term, and also represent medium-term valuable P sources, alternative to rock phosphate P fertilizers. This promising approach need further field-scale investigation to confirm the medium-long term capacity of composts to be alternative to rock phosphate P fertilizers.

Evaluation of biodegradation feasibility through rotary drum composting recalcitrant primary paper mill sludge

Primary paper mill sludge (PPMS) is the major waste expelled from the pulp and paper industries contributing soil and water pollution through the recalcitrant organic and inorganic constituents. These pollutants can, however, be transformed into a high-value soil ameliorating material with nominal investment and time. Current study therefore evaluated the potential of rotary drum composting PPMS for 20 days to delineate an environmentally sustainable option. Five trials with proportions of PPMS, cow dung and saw dust: Trial 1 (10:0:0), Trial 2 (8:1:1), Trial 3 (7:2:1), Trial 4 (6:3:1) and Trial 5 (5:4:1) were performed for evaluation of degrading and nutritive ability along with the fate of pollutants for total mass of 150 kg. Trial 4 exhibited highest metabolic activity contributing higher temperature evolution and longer thermophilic phase (10 days) owing to optimum addition of innoculum and nitrogen through the cattle manure. Moreover, degradation of 16.8% organic matter was also best achieved in Trial 4 following up first-order kinetics. Furthermore, BOD, COD and C/N ratio also explains degradation to be maximum in trial 4 (6:3:1) with reduction of 59.3%, 60.1% and C/N ratio from 55.1 to 18 respectively, proving to be the essential determining factors. Phosphorus availability increased by around 67% in trial 4. PPMS can be thus transformed into a potential valued added product and safe for subsequent land application.

Effect of iron sulphate on the phosphorus speciation from agro-industrial sludge based and sewage sludge based compost

Composting is considered a suitable process for organic waste management, providing stable products that can be safely utilized as fertilizers, but little is still known about the variation of phosphorous (P) extractability during the stabilization process. In this work, sequential chemical extraction (SCE) with increasing strength extractants (H₂O; 0.5M NaHCO₃ pH 8.5; 0.1M NaOH, 1M HCl) was applied for P speciation over 56days of composting of either agro-industrial or urban wastewater sludge with green waste treated (AIC_Fe+; SSC_Fe+) or not (AIC_Fe-; SSC_Fe-) with FeSO₄ (2%v/v). Composting strongly reduced the H₂O-P, promoting the organic-P (P_o) mineralization from the labile fraction (H₂O+NaHCO₃ 40%), in addition to the increases of NaHCO₃- and HCl-extractable inorganic-P (P_i) in both AIC_Fe- and SSC_Fe- (+20% on average). The FeSO₄ treatment did not negatively affect the process, reducing the P_o mineralization during composting by increasing the NaOH-P, also protecting this fraction from fixation in the sparingly soluble fraction. The final P fractionation (%) was in AIC_Fe-: NaOH (41)=NaHCO₃ (38)>HCl (18)>H₂O (3); in AIC_Fe+: NaOH (53)>NaHCO₃ (24)=HCl (22)>H₂O (2); in SSC_Fe-: NaOH (46)>NaHCO₃ (29)>HCl (21)>H₂O (4) and in SSC_Fe+: NaOH (66)>NaHCO₃ (13)>HCl (20)>H₂O (1). Composting reduced the more easily leachable fraction (labile-P_o), reducing the risk of P loss by increasing the long-term available P fraction (NaOH-P). This was enhanced by the FeSO₄ addition. Further investigation into soil behaviour and plant availability of P from this source is needed.

Phosphorous extractability and ryegrass availability from bio-waste composts in a calcareous soil

In this work four stable bio-waste composts (C1, C2, C3, C4) were selected on the basis of their increasing water soluble P (H₂O-P). The P speciation was assessed via sequential chemical extraction (SCE) on the same products. Moreover, the plant-available P was assessed via apparent recovery fraction approach (ARF) in a pot test on ryegrass over 21 weeks at 15 mg P kg^-1 of soil. An inorganic P source (P-chem) was added as a reference at the same P rate in addition to a non-fertilized control (Control). SCE showed that the sparingly soluble P (HCl-P) was the most important fraction in all composts: C1 (HCl 65% > NaHCO₃ 17% = NaOH 17% > H₂O 1%); C2: (HCl 51% > NaOH 23% > NaHCO₃ 18% > H₂O 7%); C3: (HCl 58% > NaOH 21% > NaHCO₃ 12% > H₂O 9%); C4: (HCl 39% > NaOH 23% > NaHCO₃ 22% > H₂O 16%). The plant test showed that the different treatments had a different ARF (%) at the first harvest: P-chem (14.7)> C4 (14.4)> C3 (14.1)> C2 (3.4)>C1 (3.1), compared to the cumulated ARF (%) of the six harvests: C4 (50.1)> C3 (35.0)> C1 (21.1)> C2 (18.3)> P-chem (17.4). Data showed a good correlation of H₂O-P vs. plant ARF at the first harvest and a good correlation of labile P (H₂O-P + NaHCO₃-P) vs. total plant ARF over 21 weeks. The free and labile P forms from SCE can be a valuable tool in the assessment of fast and middle term plant-available P from stable bio-waste composts in calcareous soils.