Effectiveness of bioactive compounds in amending the soil infested with soil-borne Ralstonia solanacearum of potato

Three natural bioactive compounds, viz. cow dung, bee propolis and turmeric powder were applied to amend the Ralstonia solanacearum infested soil of potato. Sun dried cow dung @ 30 t/ha, aqueous extraction of turmeric powder @ 30 kg/ha and propolis @ 5 lit/ha were applied to the inoculated soil by mixing with field soil in SAU (Dhaka) and BARI (Gazipur). Data on pH, organic matter, total cfu/ml and avirulent cfu/ml of the treatment applied soil and per cent disease index (PDI) of bacterial wilt of potato were recorded. Significant difference in soil pH and per cent organic matter (OM) occurred in all the amended soil as compared to control. A decreased total cfu/ml of R. solanacearum occurred in all the treated soil, but propolis (8.2 X 107) and cow dung (1.1 X 108) showed the lowest count. However, in increasing the avirulent count of R. solanacearum, turmeric powder (1.8 X 109) showed the highest count compared to other amended soil. Significant disease reduction over control was also observed in all the treatments, but propolis (45.65%) and turmeric powder (43.48%) showed the best results in wilt disease reduction. J. Biodivers. Conserv. Bioresour. Manag. 2021, 7(1): 43-50

Coupling Effects of Goat Manure and Water Management on Immobilization of Cadmium and Improvement of Bacterial Community

The objective of this study was to expound possible effect of fertilization and water management in the remediation process of hazardous substance using sepiolite(SP). Meanwhile, Illumina high-throughput sequencing was performed to investigate how the composition of the rhizosphere bacterial community responded to a series of soil remediation process. The results showed that application of SP increased pH, decreased DOM under different water condition, but goat manure (GM) increased pH and DOM at the same time. Under water-saturated condition (FWHC), the application of GM increased the content of available Cd (DTPA-Cd) by 42.0-68.9%, 13.1%-30.3% of unamended and SP-amended soil, respectively. Under normal water condition (NWHC), the application of GM increased DTPA-Cd by 0.7%-5.8%, 73.7%-115.5% of unamended and SP-amended soil, respectively. Consequently, coupling effect of FWHC and GM decreased Cd content in shoots of pak choi. We also found that the application of GM increased the abundance of soil microbial communities. Abundance of proteobacteria reached a peak when applied GM in SP-amended soil under FWHC. RDA analysis showed that soil microbes such as bacteroidetes, patescibacteria, and proteobacteria were correlated positively with pH, DOM, and DTPA-Cd. Acidobacteria was correlated positively with DTPA-Cd, and negatively with pH and DOM. The relationship of soil physicochemical properties and the bacterial community variation indicated that GM and SP mixed additives may indirectly affect the soil microbial community by changing soil physicochemical properties and available Cd content.

Transmission of Antibiotic-Resistant Escherichia coli from Chicken Litter to Agricultural Soil

A growing concern regarding the use of animal manure as fertilizer is the contamination of soil, plants, and the environment with a variety of antibiotic-resistant and pathogenic bacteria. This study quantified and characterized the antibiotic resistance profiles of Escherichia coli in soil before and after chicken litter application to determine the impact of manure on the soil resistome. Litter and soil samples were collected from a sugarcane field before and after litter application. E. coli was isolated and quantified using the Colilert®-18/Quanti-tray® 2000 and 10 randomly selected isolates from the positive wells of each Quanti-tray were putatively identified on eosin methylene blue agar. Real-time PCR was used to confirm the isolates by targeting the uidA gene. Antibiotic susceptibility test against 18 antibiotics was conducted using the disk diffusion method, and the multiple antibiotic resistance index was calculated. Soil amendment with chicken litter significantly increased the number of antibiotic-resistant E. coli in the soil. Among the 126 E. coli isolates purified from all the samples, 76% showed resistance to at least one antibiotic, of which 54.2% were multidrug-resistant (MDR). The highest percentage resistance was to tetracycline (78.1%), with the least percentage resistance (3.1%) to imipenem, tigecycline, and gentamicin. The isolates also showed resistance to chloramphenicol (63.5%), ampicillin (58.3%), trimethoprim-sulfamethoxazole (39.6%), cefotaxime (30.2%), ceftriaxone (26.0%), cephalexin (20.8%), cefepime (11.5%), amoxicillin-clavulanic acid (11.5%), cefoxitin (10.4%), Nalidixic acid (9.4%), amikacin (6.3%), and ciprofloxacin (4.2%). Of the 54.2% (52/96) MDR, the highest number was isolated from the litter-amended soil (61.5%) and the least isolates from soil samples collected before litter application (1.9%). The relatively higher mean MAR index of the litter-amended soil (0.14), compared to the soil before the amendment (0.04), suggests soil pollution with antibiotic-resistant E. coli from sources of high antibiotic use. E. coli could only be detected in the soil up to 42 days following manure application, making it a suitable short-term indicator of antibiotic resistance contamination. Notwithstanding its relatively short detectability/survival, the application of chicken litter appeared to transfer antibiotic-resistant E. coli to the soil, enhancing the soil resistome and highlighting the consequences of such agricultural practices on public health.

Can hemp hurd or paper mulch and biochar application improve weed management in matted-row strawberry production systems?

During 2015 and 2016, studies were conducted at Absaraka and Dickinson, North Dakota to evaluate the impacts of hemp (applied at 1156 m3 ha−1) and commercial paper mulch, as well as soil-applied biochar (applied at 11.25 m3 ha−1), on weed suppression and strawberry growth during the establishment year, and on weed suppression and strawberry yield during the production year, in a matted row production (MRP) system. During 2015, biochar influenced dry weed biomass only within the hemp mulch, with slightly more weed biomass associated with biochar application compared to zero biochar (3.1 vs 0.4 g m−2), suggesting that biochar may have increased weed germination and/or emergence from beneath hemp mulch. Biochar application also slightly increased soil pH, from 6.9 in non-amended soil to 7.0 in amended soil. Strawberry runner number during 2015 was greater in association with hemp or paper mulch compared to zero mulch (4.5 and 4.9 vs 2.4 runners plant −1, respectively). This result mirrored a similar differential in per berry mass across sites (7.6 and 7.4 vs 6.2 g berry −1 for hemp mulch, paper mulch and zero mulch, respectively). These results may be related to hemp and paper mulch reducing maximum soil temperatures during summer 2015. During the establishment year, both hemp and paper mulch suppressed weeds well compared to zero mulch, although at Absaraka hemp mulch provided slightly better weed suppression than paper mulch. During the production year, both mulches continued to suppress weeds compared to zero mulch at Dickinson. However, at Absaraka, only hemp mulch provided weed suppression compared to zero mulch, possibly because of faster paper degradation caused by greater numbers of large precipitation events and greater relative humidity at Absaraka compared to Dickinson. Weeds were removed from plots during 2015 to allow separation of weed suppression from other possible mulch impacts; therefore, yield data do not reveal striking differences among mulch treatments. Because previous research has demonstrated the impact of weed management during the establishment of strawberries in a matted row system, we concluded that hemp mulch may provide more durable weed suppression compared to paper mulch, which would increase strawberry yield protection in an MRP system. Material cost may be an issue for implementing hemp mulch, as hemp hurd cost was 25 times paper mulch at the application rates used in this study. However, hemp mulch could still be a beneficial option, especially for organic strawberry growers desiring a renewable and environmentally sound replacement for plastic mulch who are able to find affordable local sources of this material.