Exploring the Microbial Dynamics of Organic Matter Degradation and Humification during Co-Composting of Cow Manure and Bedding Material Waste

The present study investigated the effects of bedding material (BM) waste on physicochemical properties, organic matter (OM) degradation, microbial community structure and metabolic function during composting. The results showed that bedding material (CK-0, S1-40%, S2-25%) optimized the composting conditions for lignocellulose and OM biodegradation. The highest OM degradation and humic substance (HS) synthesis rates were observed in the 40% BM addition group. Firmicutes was more abundant in the bedding material addition groups, whereas Proteobacteria was more abundant in the group without bedding material. Functional prediction showed higher carbohydrate and amino acid metabolism in the BM groups than that in control group. Animal and plant pathogens were almost eliminated, and saprotrophs were the dominant fungal trophic modes after 40% BM addition composting. Cellulose, hemicellulose, and organic matter had strong associations with microbial communities, such as Lysinibacillus and Corynebacterium (bacteria), compared to the associations of Aspergillus, Candida, and Sordariomycetes (fungi) (p value < 0.05). Network analysis revealed closer microbial community interactions in 40% BM addition group than in other groups. These findings provide detailed information about the coupling of material conversion, of bacterial and fungal succession during composting, and that bedding materials waste can also be used as an effective compost amendment.

Example Ordinance for Compost Amending Soil in Urban Landscaping

This publication describes an example ordinance that can be used by local governments as a starting point for developing a compost amendment ordinance tailored to their local situation and conditions. Written by Jovana Radovanovic, James D. McGuire, Jana Caracciolo, Tom Ankersen, and Eban Z. Bean, and published by the UF/IFAS Department of Agricultural and Biological Engineering, October 2021.

Amending Soil With Biochar From Available Agricultural Wastes to Improve Sustainability of Cotton Production in Mali

Improving the sustainability of cotton production in Mali can be achieved by returning organic matter and nutrients to degraded soils. Amendment with biochar prepared from locally available feedstocks has been suggested as a pathway to sustainability. A greenhouse study was conducted to evaluate the effect of biochar prepared from two feedstocks readily available in Mali, cotton field residue and rice hulls, on cotton plants grown to six weeks. A composted municipal biosolid was included for comparison with the more carbon-stable biochars. Four soils of contrasting properties were included in the study. Plants were measured for shoot height and mass, root length and mass, whole plant tissue nutrients, and arbuscular mycorrhizal fungi (AMF) colonization in roots. Shoot height was often improved by amendment in all soils. Root mass was improved by amendment only in the soil with the greatest clay content. Nitrogen (N) uptake was significantly depressed, and phosphorus (P) uptake was increased under biochar and compost amendment in the most coarsely textured soil. No effect on N and P uptake was observed in the soil with the greatest clay content. Ridge regression analysis showed that AMF root colonization was positively related to the P content of the amendments (1.411*Pamend), negatively related to soil P (-0.486*Psoil) and positively related to both soil pH (2.153*pH) and clay content (1.129*clay%). Results indicate that degraded soils may be restored through amendment with biochar created from locally available feedstock to improve sustainability of cotton production. Soil properties will determine the degree of benefit.

Integrated Bioplant and Groundnut Husk Biochar Compost Application on Yield of Lettuce in a Rhodic Kandiustalf

Bioplant is a liquid soil conditioner that contains a consortium of beneficial fungi and bacteria manufactured by Artemis and Angel Company Limited in Bangkok. Bioplant is purported to stimulate beneficial microbial activity in soil and hence increase crop yield. However, the efficacy of Bioplant has not been evaluated on Ghanaian soils. A screen house trial was consequently conducted to evaluate the efficacy or otherwise of Bioplant on the yield of lettuce in a Rhodic Kandiustalf amended with or without compost. The soil was mixed with compost at 20 parts soil to 80 parts compost and 60 parts soil to 40 parts compost (v/v) and potted in 1.7-L pots. There was another potted soil with no compost amendment. To each of these potted soils, Bioplant was applied at four rates, viz., zero, half the manufacturer's recommended rate, the manufacturer's recommended rate, and twice the manufacturer's recommended rate, and allowed to equilibrate for 2 weeks. Seedlings of lettuce of the variety Eden were transplanted into the pots, and the treatments kept at 80% field capacity. The treatments were replicated four times in a completely randomized design. At physiological maturity, the lettuce was harvested, and fresh and dry matter yields were taken. The C and N contents and N uptake in the harvested plants were also determined. Results indicate that conditioning the soil with Bioplant at half and the manufacturer's recommended rates increased N uptake, resulting in higher carbon accumulation with concomitant increases in both fresh and dry matter yields. The results also show that amending the Rhodic Kandiustalf with Bioplant at twice the manufacturer's rate suppressed yield. Application of Bioplant at the manufacturer's recommended rate in combination with compost amended at 40 parts to 60 parts soil (v/v) saw a 47 and 90% respective significant yield increases in fresh weight and dry matter when only Bioplant was applied at the manufacturer's recommended rate. It is therefore recommended for Bioplant to be applied at the manufacturer's recommended rate of 825 mL/ha in combination with 40 parts of compost to 60 parts of soil (v/v).

Urban Naturalization for Green Spaces Using Soil Tillage, Herbicide Application, Compost Amendment and Native Vegetation

Naturalization is a new and promising ecological approach to green space development for urban environments, although knowledge is sparse on techniques to implement it. We evaluated naturalization of eight native trees and shrubs, with site preparation (tillage, herbicide) and soil amendment (compost rates) treatment combinations at six sites in the city of Edmonton, Alberta, Canada. Soil texture improved with all compost rates, and acidity, electrical conductivity and total carbon increased, especially with 100% compost. Soil nutrients generally increased with compost then declined within a year. Plant species with highest potential for use in urban green spaces were Picea glauca, Symphoricarpos albus and Rosa acicularis. Herbicide was the most influential site preparation treatment, positively increasing survival and growth of planted woody species, while negatively lowering non-native species cover and increasing noxious weed cover. Soil amendment with compost influenced cover not species richness, with high compost amendment reducing vegetation cover across sites, and increasing individual plant size. This study suggests amendment of soil with compost and appropriate site preparation can positively influence naturalization of these woody species for urban green spaces.

Integrated Metagenomic Assessment of Multiple Pre-harvest Control Points on Lettuce Resistomes at Field-Scale

An integrated understanding of factors influencing the occurrence, distribution, and fate of antibiotic resistance genes (ARGs) in vegetable production systems is needed to inform the design and development of strategies for mitigating the potential for antibiotic resistance propagation in the food chain. The goal of the present study was to holistically track antibiotic resistance and associated microbiomes at three distinct pre-harvest control points in an agroecosystem in order to identify the potential impacts of key agricultural management strategies. Samples were collected over the course of a single growing season (67 days) from field-scale plots amended with various organic and inorganic amendments at agronomic rates. Dairy-derived manure and compost amendment samples (n = 14), soil samples (n = 27), and lettuce samples (n = 12) were analyzed via shotgun metagenomics to assess multiple pre-harvest factors as hypothetical control points that shape lettuce resistomes. Pre-harvest factors of interest included manure collection during/post antibiotic use, manure composting, and soil amended with organic (stockpiled manure/compost) versus chemical fertilizer. Microbial community resistome and taxonomic compositions were unique from amendment to soil to lettuce surface according to dissimilarity analysis. The highest resistome alpha diversity (i.e., unique ARGs, n = 642) was detected in amendment samples prior to soil application, while the composted manure had the lowest total ARG relative abundance (i.e., 16S rRNA gene-normalized). Regardless of amendment type, soils acted as an apparent ecological buffer, i.e., soil resistome and taxonomic profiles returned to background conditions 67 d-post amendment application. Effects of amendment conditions surprisingly re-emerged in lettuce phyllosphere resistomes, with the highest total ARG relative abundances recovered on the surface of lettuce plants grown in organically-fertilized soils (i.e., compost- and manure-amended soils). Co-occurrence analysis identified 55 unique ARGs found both in the soil amendments and on lettuce surfaces. Among these, arnA and pmrF were the most abundant ARGs co-occurring with mobile genetic elements (MGE). Other prominent ARG-MGE co-occurrences throughout this pre-harvest lettuce production chain included: TetM to transposon (Clostridiodies difficile) in the manure amendment and TriC to plasmid (Ralstonia solanacearum) on the lettuce surfaces. This suggests that, even with imposing manure management and post-amendment wait periods in agricultural systems, ARGs originating from manure can still be found on crop surfaces. This study demonstrates a comprehensive approach to identifying key control points for the propagation of ARGs in vegetable production systems, identifying potential ARG-MGE combinations that could inform future surveillance. The findings suggest that additional pre-harvest and potentially post-harvest interventions may be warranted to minimize risk of propagating antibiotic resistance in the food chain.

Isotope fractionation (δ 13C, δ15N) and microbial community response in degradation of petroleum hydrocarbons by biostimulation in contaminated soil

This study investigated the isotope effects of δ13C and δ15N and microbial response during biodegradation of hydrocarbons by biostimulation with nitrate or compost in the petroleum-contaminated soil. Compost and KNO3 amendments promoted the total petroleum hydrocarbon (TPH) removal accompanied by a significant increase of Actinobacteria and Firmicutes phyla. Soil alpha diversity decreased after 90 days of biostimulation. An inverse significant carbon isotope effect (εc = 16.6 ± 0.8‰) and strong significant nitrogen isotope effect (εN = -24.20 ± 9.54‰) were shown by the KNO3 supplementation. For compost amendment, significant carbon and nitrogen isotope effect were εc = 38.8 ± 1.1‰ and εN = -79.49 ± 16.41‰, respectively. A clear difference of the carbon and nitrogen stable isotope fractionation was evident by KNO3 or compost amendment, which indicated the mechanisms of petroleum degradation by adding compost or KNO3 are different.

Structural and Functional Shift in Soil Bacterial Community in Response to Long-Term Compost Amendment in Paddy Field

Microbial community composition and diversity of agricultural soils primarily depend on management practices. The application of compost on agricultural fields is known to increase soil fertility, which can also help to enhance agricultural productivity. The effects of long-term application of compost along with nitrogen (N), phosphorus (P), and potassium (K) (+Compost) on soil bacterial diversity and community profiles were assessed by amplicon sequencing targeting the 16S rRNA gene of bacteria and compared with those on soils that received only NPK but not compost (−Compost). Ordination plot showed treatments to cluster differently, implying changes in community composition, which were validated with taxonomical data showing Firmicutes, Actinobacteria, and their related classes to be significantly higher in +Compost than in −Compost soils. The predicted abundance of functional genes related to plant growth promotion, development, and decomposition was significantly higher in compost-amended soil than in soils without compost. The results are of particular importance as they provide insights into designing management practices to promote agricultural sustainability.