Effect of fish emulsion used as a preplanting soil amendment on verticillium wilt, scab, and tuber yield of potato
Abstract and Figures
Fish emulsion is used mainly as a fertilizer for crop production but, in a previous study, we have demonstrated its efficacy in suppressing damping-off [Rhizoctonia and Pythium spp.] in radish and cucumber in a peat-based substrate or soil. In the present study, fish emulsion was tested as a preplanting soil amendment to control soilborne diseases of eggplant and potato such as verticillium wilt [Verticillium dahliae and Verticillium albo-atrum] and scab [Streptomyces spp.]. Tests were conducted on 11 soils with different characteristics (pH, 5.2–7.2; organic-matter content, 1.0%–3.7%), originating from commercial potato fields in Ontario, New Brunswick, and Prince Edward Island with a history of verticillium wilt and scab. The amendment of soil with fish emulsion at rates of 0.5% and 1% (m/m) protected eggplant from verticillium wilt, and the 1% fish-emulsion treatment increased fresh and dry plant biomasses in the greenhouse. Microplot experiments with potato showed that the 1% fish-emulsion treatment significantly (P < 0.05) reduced scab severity (by 0.6–2.1 units on a scale of 0–6) in seven soils with low to moderate scab-disease pressure and significantly increased total tuber yield (by 41%–170%) in nine soils, compared with the control treatments. Fish emulsion also reduced potato petiole infection by V. dahliae in one soil. In potato field trials at two sites in 2004, treatment with 1% fish emulsion (20 000 L/ha) significantly (P < 0.05) reduced scab severity (by 0.8–1 units) and significantly increased scab-free tubers (by 132%–366%) and marketable-tuber (surface scab < 5%) yield (by two fold), compared with the control treatments. Total tuber yield was reduced at one site and not affected at the other. No effect of fish emulsion on scab and verticillium wilt or tuber yield was observed in a 2005 field trial. The reduction of scab or verticillium wilt by fish emulsion was not soil-specific and varied from year to year. The results indicated that fish emulsion was not effective in soils with high disease pressure.
![Effect of fish-emulsion preplanting soil amendment on potato scab [Streptomyces spp.] severity (A) and tuber yield (B) in microplot trials in 2003 on five soils from Ontario commercial potato fields (sites B2, GM, D, and GH) with a history of verticillium wilt [Verticillium dahliae and Verticillium albo-atrum] and potato scab. Fish emulsion was incorporated into the soils in the spring of 2003 at a rate of 1% (m/m). Tubers were harvested in the fall and rated for scab severity, using a scale of 0-6 (see Table 1 for definition), and the yield was determined. Values (mean + standard error) are the average of five replicates. Different letters above the bars within a site indicate a significant difference in scab severity or yield (P < 0.05), according to Student-Newman-Keuls test. The numbers in parentheses below each site denotes pH.](https://www.researchgate.net/profile/George-Lazarovits/publication/242564170/figure/fig1/AS:668998605754377@1536513105428/Effect-of-fish-emulsion-preplanting-soil-amendment-on-potato-scab-Streptomyces-spp_Q320.jpg)
![Effect of fish-emulsion preplanting soil amendment on potato scab [Streptomyces spp.] severity (A) and tuber yield (B) in microplot trials in 2005 on three soils from Ontario commercial potato field sites (B2, L1, and V4) with a history of verticillium wilt [Verticillium dahliae and Verticillium albo-atrum] and potato scab. Fish emulsion was incorporated into the soils in the spring of 2005 at a rate of 1% (m/m). Tubers were harvested in the fall and rated for scab severity, using a scale of 0-6 (see Table 1 for definition), and yield was determined. Values (mean + standard error) are the average of six replicates. Different letters above the bars within each site indicate a significant difference in scab severity or yield (P < 0.05), according to Student-Newman-Keuls test. The number in parentheses below each site denotes pH.](https://www.researchgate.net/profile/George-Lazarovits/publication/242564170/figure/fig2/AS:668998605742083@1536513105450/Effect-of-fish-emulsion-preplanting-soil-amendment-on-potato-scab-Streptomyces-spp_Q320.jpg)
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... Fish emulsion contains a mixture of organic acids which have a deleterious effect on fungal spores. According to Abbasi et al. (2006), fish emulsion added to a sandy loam soil at the rate of 2% (w/w) reduced the viability of Verticillium dahliae microsclerotia by 74% in 1 day, 98% in 3 days and 99% in 6 days. The toxicant responsible for the immediate kill of microsclerotia is a mixture of organic acids including glycolic, acetic, formic, n-butyric and propionic acids (Abbasi et al., 2006). ...
... According to Abbasi et al. (2006), fish emulsion added to a sandy loam soil at the rate of 2% (w/w) reduced the viability of Verticillium dahliae microsclerotia by 74% in 1 day, 98% in 3 days and 99% in 6 days. The toxicant responsible for the immediate kill of microsclerotia is a mixture of organic acids including glycolic, acetic, formic, n-butyric and propionic acids (Abbasi et al., 2006). Similar results were obtained when applying fish emulsion to soils and monitoring damping-off (Pythium) disease on cucumbers. ...
The mode of persistence of Phytophthora cinnamomi, a highly aggressive soil- and water-borne pathogen, remains unclear. This study investigated the survival of viable oospores and chlamydospores of P. cinnamomi when present as free propagules in untreated soil, or in soil subject to four exogenous treatments: smoke water, fish emulsion and two fungicides (ridomil and furalaxyl). The exogenous treatments were applied under moist and dry soil conditions. Spore viability was determined by the thiazolyl blue tetrazolium bromide (MTT) staining technique, with a qPCR assay used to compare general patterns of decline. Over 96% of oospores lost viability over a period of 48 weeks irrespective of soil moisture conditions. The mean percentage viability for oospores decreased from 91% at time zero to 72, 35, 20 and 1% after 6, 12, 24 and 48 weeks, respectively. Reduction in viability of chlamydospores was more rapid than oospores, with viability declining from 92% to zero after 12 weeks. There was no significant difference between untreated soil and the exogenous treatments. The RNA-based qPCR assay indicated a strong presence of viable oospores of P. cinnamomi up to week 12 for moist soil and week 3 for dry soil, but thereafter failed to detect RNA even though viable oospores could be detected by MTT staining. Based on the MTT staining, this study indicated that viability of P. cinnamomi oospores may be entirely lost within 1 year and that of chlamydospores within 3 months for the soil type tested. Therefore, oospores and chlamydospores when existing as free propagules in soil appear unlikely to be involved in the long-term survival of P. cinnamomi.
... During the early or vegetative stage of development, FAA is used as a nitrogen source to improve the growth and size of the plant (Weinert et al., 2011b). It was mentioned that fish emulsion can be used on soil to reduce soil-borne disease in soil with moderate disease pressure (Abbasi et al., 2006). Nitrogen (N), potassium (K), phosphorus (P), calcium (Ca), and rhizobacteria are nutrients found in vermin tea that support plant growth and help to start the formation, growth, and accumulation of soil organic matter (Aslam and Ahmad, 2020). ...
A field experiment was conducted to evaluate the efficacy of foliar sprays of different organic fertilizers on the growth and yield of okra (Abelmoschus esculentus L.) at the Institute of Agriculture and Animal Science, Rupandehi, Nepal, from April to July 2022. "Arka Anamika" variety of okra was used. With five treatments and four replications, the experiment was arranged in a randomized complete block design (RCBD). The treatments used were control, fish amino acid (FAA), moringa fermented plant juice (FPJ), Ipil-Ipil fermented plant juice, and vermicompost tea. The data collected after applying these treatments were analyzed using R-Studio version 4.2.1. Among the treatments used, fish amino acid produced a significantly higher yield (14.26 tons/hectare) than moringa FPJ (12.82 tons/hectare), Ipil-Ipil FPJ (12.44 tons/hectare), vermicompost tea (11.67 tons/hectare), and control (11.16 tons/hectare). The result also revealed that different treatments significantly affect plant height, number of leaves, number of branches, and number of buds, with a 0.05 level of significance. The maximum number of leaves (37.97), number of branches (5.88), pod length (15.33 cm), bud number (12.70), and fruit weight (18.87 grams) were observed in FAA, while control showed the least among all treatments. Therefore, the result indicated that fish amino acid is a more potential organic fertilizer than moringa FPJ, Ipil-Ipil FPJ, and vermicompost tea for okra production.
... Fish can accumulate heavy metals in their marine environment, which can then be transferred to soil and plants; high nitrogen content can lead to nutrient runoff if overapplied. [112][113][114][115] Seaweed Extracts USD 25 per quart Improves yield in tomato. ...
Organic farming, which is deeply rooted in traditional agricultural practices, has witnessed a profound evolution over the last century. Transitioning from a grassroots initiative resisting the industrialization of agriculture to a global industry, organic farming now plays a pivotal role in addressing contemporary challenges related to environmental health, sustainability, and food safety. Despite the growing consumer demand for organic products and market access, organic farming has its challenges. This paper discusses the origin and evolution of organic farming with an emphasis on different types of organic fertilizers, benefits, and challenges. Nutrient variability and the slow-release nature of organic fertilizer often do not meet crop demands and can substantially reduce yield. Some organic fertilizers, like manure and biosolids, can provide a higher yield benefit, but there are environmental and health risks associated with them. Weed and pest management in organic farming can be labor-intensive and increase costs. Inefficient planning of organic farming and rapid transition can also create food insecurity. This paper also gives a brief account of the current certification process for organic fertilizers and their technicalities. It showcases how the holistic approach of organic farming extends beyond production, including strategies like reducing food waste and building self-sufficient farming communities. These practices contribute to a more sustainable agricultural system, reducing environmental impacts and supporting local economies. Future technological innovations, especially in precision agriculture and bio-physicochemical models, can help in formulating targeted organic fertilizers.
... The fish wastes rich in nitrogen, potassium, phosphorus and trace minerals (Ghaly et al., 2013) can serve as raw material. Fish emulsion is a liquid byproduct of the fish meal (Abbasi, 2006). ...
Sudden food shortage due to strict green agriculture policy, economic crisis, COVID pandemic situation instruct the importance of home level organic production of good quality fruits and vegetables. Therefore, an experiment was conducted to test the efficacy of organic liquid fertilizers formulated from fish, livestock's and plant wastes on leafy vegetable green Amaranth to promote home gardening. The liquid fertilizer was tested on Amaranth grown separately in vemicompost and garden compost. The 7 kg capacity pots were filled with two media (medium 1: vemicompost; medium 2: garden compost) and arranged in CRD with four replicates with each medium. Five plants of green-amaranth per pot were planted and treated with fish emulsion + vermi-tea (1:4=T1), cow urine + vermi-tea (1:4=T2), three leaves [Neem+ Giliricidia+ Candle bush] solution + vermi tea (3:1=T3), vermi tea (T4) and control (T5) at the rate of 50 mL/pot on 2 nd , 4 th and 6th week after planting. Agronomic and yield data were collected and subjected to ANOVA using SAS. Tukey's HSD multiple comparison test and PROC CORR was used to determine the best treatment combination at P <0.05. The results revealed that there was significant difference in N, P and K content of the treatments tested. The plant height, leaf area, number of leaves, root shoot ratio was significantly higher in fish emulsion + vermi-tea (1:4) [T1] and cow urine + vermi-tea [T2] at 8 th weeks after planting in vermi-compost medium. There was strong and positive correlation (R 2 > 0.8) among yield parameters, and root: shoot ratio with N, P K content of the liquid fertilizers tested in vermi-compost medium. Therefore, this investigation concludes that the fish emulsion + vermi-tea (1:4) and cow urine + vermi-tea (1:4) are good combination to use as liquid fertilizer at the rate of 50mL/Pot to get best yield in vermi-compost medium.
... Many studies showed also CS reductions with the addition of various organic materials, including compost [95], peat [33], green manure [92,96], several types of animal manure [83,97,98] and fish emulsion [21] (Table 2). Although the effect of organic amendments was found to be mostly beneficial, rarely were the causes for the observed effects on CS (intensification or suppression) resolved. ...
Nature-friendly approaches for crop protection are sought after in the effort to reduce the use of agrochemicals. However, the transfer of scientific findings to agriculture practice is relatively slow because research results are sometimes contradictory or do not clearly lead to applicable approaches. Common scab of potatoes is a disease affecting potatoes worldwide, for which no definite treatment is available. That is due to many complex interactions affecting its incidence and severity. The review aims to determine options for the control of the disease using additions of micronutrients and modification of microbial communities. We propose three approaches for the improvement by (1) supplying soils with limiting nutrients, (2) supporting microbial communities with high mineral solubilization capabilities or (3) applying communities antagonistic to the pathogen. The procedures for the disease control may include fertilization with micronutrients and appropriate organic matter or inoculation with beneficial strains selected according to local environmental conditions. Further research is proposed to use metagenomics/metabolomics to identify key soil–plant–microbe interactions in comparisons of disease-suppressive and -conducive soils.
... Highbush blueberry plants fertilized with fish emulsion had more leaf and 1-year-old wood dry weight than those fertilized with feather meal (Larco et al., 2013a). The Agrothrive and TRUE402 fertilizers (Table 6) showed no differences for plant growth, yield, or fruit quality, and were considered appropriate for planting establishment USA (Cox, 2010;Cox and Eaton, 2011;Eaton et al., 2013) Canada (Abbasi, 2013;Abbasi et al., 2004;Abbasi et al., 2006;Abbasi et al., 2003) Hydrolyse fish and seaweed fertilizer (OMRI certified) USA (Russo, 2006) (continued on next page) in blackberry (Fernandez-Salvador et al., 2015a). Blackberry cultivars, after fertilization with TRUE402, Phyta-Grow Ò Leafy Green Special TM (pelletized soy meal), and pelletized processed poultry litter showed a similar response to these fertilizers (Fernandez-Salvador et al., 2015b). ...
This paper reviews relevant knowledge about the production and uses of fertilizers from fish and fish waste (FW) that may be applicable for certified organic farming, with a focus on crop and horticultural plants. Fish industries generate a substantial amount of FW. Depending on the level of processing or type of fish, 30–70% of the original fish is FW. Circular economy and organic farming concepts were used to evaluate the potential of production of fertilizers from captured fish. Fertilizers produced from captured fish promote the recycling of nutrients from the sea and back to terrestrial environments. Nutritional composition of FW is assessed to determine the potential to supply plant nutrients such as nitrogen, or a combination of nitrogen and phosphorous, or to enrich a compost. Methods used in processing of FW to produce fish- emulsion, fish hydrolysate/fish silage, fish-compost and digestate from anaerobic digestion/co-digestion are presented. Using information about commercially available fish-based fertilizers listed by the Organic Materials Review Institute (OMRI), we present a scenario for establishing fish/FW-based fertilizers industry and research in Europe. With Norway’s 9th position among top ten global capture producers and focus in Norway on developing organic farming, we brief how FW is currently utilized and regulated, and discuss its availability for possible production of FW-based organic fertilizers. The amount of FW available in Norway for production of fertilizers may facilitate the establishment of an industrial product that can replace the currently common use of dried poultry manure from conventional farming in organic farming.
Clubroot disease management has been aimed to target all the three stages of disease cycle. The first most important step is to bring inoculum load in the soil below minimum threshold level of resting spores. The second and third steps are to suppress primary root hairs infection and secondary cortical infections, respectively, which results in club formations to continue life cycle of pathogen, P. brassicae. Any activity that results in transport of soil or crop residues infested with P. brassicae from one point to another has the potential to disseminate the pathogen. The most effective cultural control is through removal of diseased plants, improved drainage, deep plowing, ridging, long crop rotation (more than 3 years), using clean and treated seed, avoiding application of raw manures, sanitization (cleaning and disinfecting of machinery, equipment, vehicle, tools, footwear, seed drill, plant materials, irrigation water, etc.), and manipulating date of sowing keeping in mind that sow the crop seed when soil temperature is too cold for clubroot pathogen development. Use of clean, treated seeds, crop rotation, bait crops with resistant, susceptible, and non-Brassica plants reduce clubroot inoculum in the infected fields. Soil solarization in combination with low rates of fumigation (Dazomet) can be a means of clubroot control. Post harvest weed management along with susceptible host plants is a very crucial factor to reduce inoculum potential in the fields. Several simple low-cost cultural strategies may be useful for effective management of disease in the endemic areas. Intercropping of Brassica and flaxseed reduces clubroot with increase in yield. Soil amendment with lime, wood ash, or calcium cyanamide increases soil pH and is an important clubroot management strategy. Judicious use of nutrients like N, P, K, Ca, B, molybdenum, and organic matter helps in management of clubroot through maintenance of pH with conducive effects on host growth and suppressive soil environment for pathogen infection and development. Several chemicals used as soil drench, surfactant, and soil fumigants control clubroot through inhibition of resting spores germination and suppression of root hairs and cortical infection. Clubroot has been managed with the use of biological agents of bacterial, fungal, and plant products origin which produce antimicrobial metabolites against P. brassicae and colonize host roots to induce resistance. Commercial biofungicides like Serenade, Prestop, Mycostop, and granulate formulations Plasma soil, and Root Shield Plus with fungicides like fluazinam, and cyazofamid are very effective against clubroot. Disease management through host resistance is the most economical and ecofriendly strategy. Disease-resistant cultivars of Brassica crops have been developed and are being used to manage clubroot in countries like Canada, China, Australia, Japan, Germany, and Korea. Integrated approaches using cultural, chemical, biological, and host resistance have been extremely effective for clubroot management strategy along with high yield of cruciferous crops. In Latin American countries, clubroot has been managed with modification of cultural operations depending on soil environment, pH, and inoculum load in each country, in addition to the growing of resistance cvs. and using biological and chemical control strategies.
Intensive agriculture requires large inputs of chemicals to avoid losses caused by pathogen infections. Exploring the rhizosphere of plants, which is an area with enormous abundance and diversity of microorganisms, represents a promising strategy to protect plants from pathogens in a sustainable way. Recent studies revealed the importance of soil microbiome in the process of natural plant defense and how current management practices can interfere in the dynamics of these microbial communities shaping a protective microbiome. This review emphasizes the main findings related to changes in rhizosphere microbiome composition and functions during plant infection by soilborne pathogens. Understanding plant-microbiome interactions in the rhizosphere is key to develop microbiome-based strategies for assembling beneficial protective resident microbial communities in production systems.
It is claimed that the addition of organic amendments to growing media enhances plant growth in numerous ways including by supplying nutrients, directly promoting growth, improving flowering and fruiting, enhancing populations of beneficial microbes, and suppressing pests and diseases. Yet, there has been a paucity of robust scientific assessment of these claims, especially in containerized plant production. The aim of this review was to evaluate the efficacy of non-compost-based organic amendments in containerized production horticulture including fish emulsions; seaweed extracts; biochar; uncomposted plant parts; and uncomposted organic waste materials. Their positive and negative attributes, usefulness and typical application rates in specific production systems, and knowledge gaps are established. Non-compost-based organic amendments being such a broad group makes drawing general conclusions about their usefulness in containerized plant production problematic. However, seaweed extracts have the widest application in vegetable and ornamental species, though the question of the sustainability of their production requires further investigation.
Fusarium oxysporum Schlechtend.:Fr. f. sp. conglutinans (Wollenweb.) W.C. Snyder & H.N. Hans. causes fusarium wilt in canola (Brassica napus L.). Using cultivars with resistance is the only major form of control currently avail-able. Therefore, quick and simple methods of screening lines could benefit breeding for resistant cultivars. Two temperatures (22 and 24 °C), two soil types (the soilless mix Sunagro and a Sunagro–vermiculite mix in a ratio of 1:1),four cultivars (‘45A55’, ‘Bianca II’, ‘DS-Roughrider’ (susseptible), and ‘InVigor 5020’ (resistant)) were used to develop a simple protocol for screening resistant canola lines or cultivars. Dried mycelial inoculum on wheat grain was applied to soil at seeding, and plants were rated weekly for28 days after seeding. Plants at 24 °C had a significantly higher wilt severity than those at 22 °C, suggesting that the higher temperature of 24 °C would provide increased dis-ease severity for screening. Soil type had no significant effect on wilt severity. ‘45A55’ developed the highest wilt severity with a final rating of 83%. ‘Bianca II’ and ‘DS-Roughrider’ showed no significant differences in wilt severities (77% and 78%, respectively), while ‘InVigor5020’ was significantly more resistant, with a severity of 1% at the final rating. This protocol repeatedly distinguished resistant and susceptible cultivars at each temperature and soil type. However, the Sunagro soil alone was more manageable than the more porous, 1:1 Sunagro–vermiculite mix, which required frequent watering.
Fish soluble nutrients (FSN) applied at weekly or biweekly intervals gave comparable growth and fruit yield of greenhouse-grown tomatoes ( Lycopersicon esculentwn mill.) as plants fertilized with full strength Hoagland’s nutrient solution. FSN fertilization stimulated vegetative growth and delayed flowering and fruit-ripening by 5-8 days depending upon concentration and frequency of application. FSN can be a useful nutrient source for crop fertilization.
Tenuta, M., Conn, K. L., and Lazarovits, G. 2002. Volatile fatty acids in liquid swine manure can kill microsclerotia of Verticillium dahliae. Phytopathology 92:548-552. Liquid swine manure added to acidic soils killed microsclerotia of the wilt fungus Verticillium dahliae. We investigated whether volatile fatty acids (VFAs) in the manure were responsible for this toxicity. The survival of microsclerotia was determined after exposure to various dilutions of manure or its VFA components. Acetic, propionic, and isobutyric acids constituted the major VFAs in the manure, while n-butyric, n-valeric, iso-valeric, and n-caproic acids were present in lesser amounts. Formic acid was not detected. The individual VFAs were more toxic to microsclerotia as the solution pH was decreased, indicating that the protonated forms of the VFAs were toxic (e.g., acetic acid and not acetate). The effective concentration reducing germination of microsclerotia by 95% (EC 95) for formic and n-caproic acids was approximately 4 mM, the most toxic of the acids tested; for n-valeric, the EC 95 was 9.2 mM, isovaleric was 16.1 mM acids, and acetic, propionic, n-butyric, and isobutyric acids were approximately 30 mM. The toxicity of acetic acid, and likely all the others, was directly related to the duration of exposure. Inhibition of microsclerotia germination followed identical trends in solutions of the manure or in a mixture of VFAs with equivalent concentrations of the individual acids found in the manure. Similarly, germination declined to the same extent in the atmosphere above the manure or the VFA mixture, confirming the toxicity of VFAs to microsclerotia. Thus, under acid conditions, VFAs in liquid swine manure can kill microsclerotia of V. dahliae.
Organic amendments such as meat and bone or soybean meal, poultry or liquid swine manure, and fish emulsion significantly reduced disease in some soils tested, but had no effect in others, and sometimes increased disease severity. To understand this apparent variability we investigated the modes of action of such amendments. Depending upon the type and amount of amendment used and the characteristics of the soil, the amendments killed microsclerotia of Verticillium dahliae by ammonia, nitrous acid, and/or volatile fatty acid toxicity; and/or reduced microsclerotia survival or disease by unknown mechanisms, possibly by stimulating biological control. The most important factor affecting disease control efficacy was soil pH as the toxic products responsible for killing pathogens exist only when the soil pH was below 6 or above 8. From an understanding of the modes of action, amendments can be formulated to improve efficacy and reduce variability. This includes basing application rates upon soil properties, manipulating amendment and/or soil pH, altering the rates of nitrification and organic matter contents, screening of amendments for appropriate chemistries, improving storage conditions, altering their microbiology, and improving the timing and mode of application.
Field research, conducted for six seasons (1991-1996) on one soil type, compared organic amendments (three formulations of fish bone meal (FBM) and a marine sediment enriched with fish, lobster, and crab meal) with an NPK chemical fertilizer (17-17-17) and a zero-N control (0-17-17). Each fertilizer material was applied preplant at 80 kg N ha-1 to the same plot for six seasons that spanned two cycles of a three-crop rotation of seeded carrots, green beans, and transplanted cabbage. In plots receiving the organic amendments, soil pH and Ca increased over time compared with those plots receiving 17-17-17. The increase of soil Mg was greatest in plots receiving the fortified marine sediment treatment. Soil and leaf K values were lowest with the FBM treatment, reflecting its low K composition (6-10-1). Soil and foliar P values from the organic amendment plots were higher than those from the 17-17-17 plots. Foliar N, Ca, Mg, Fe, and B were not consistently affected by 17-17-17 or the organic amendments, but foliar Mn was higher in crops receiving 17-17-17. Marketable yields of cabbage and carrots in plots receiving the organic amendments were comparable with those from 17-17-17, but marketable yields of green beans were consistently higher in plots receiving 17-17-17. Soil and foliar results indicate that the cumulative effect of repeated application of these organic amendments is not detrimental to plant growth, and that these amendments produce marketable yields of cabbage and carrot equivalent to those of the chemical fertilizer.
Forming Latin species names (specific epithets) as 'nominative nouns in apposition' (according to Rule 12c of the International Code of Nomenclature of Bacteria) has often been misunderstood or posed problems. Here, this grammatical construction is explained, and 24 cases that did not meet the requirements for this type of construction are corrected to a genitive noun or adjectival form in agreement with Rule 12c.