Rhizosphere-associated microbiota of Canavalia ensiformis in sulfentrazone bioremediation.

The objective of this study was to determine the efficiency of the microbial rhizosphere (Canavalia ensiformis) in the phytoremediation of sulfentrazone using quantification methods (CO2 evolution, microbial biomass carbon, and metabolic quotient) and identification of bacteria (PCR-DGGE technique). The experiment was conducted in a completely randomized design, in a 2x4 factorial scheme, with four replications. The treatments were composed of rhizospheric soil (cultivated with C. ensiformis) and non-rhizosphere soil (uncultivated soil); and four levels of contamination by sulfentrazone (0, 200, 400, and 800 g ha-1 a.i.). The microbiota associated with the rhizosphere of C. ensiformis efficiently reduced sulfentrazone residues in the soil, with better performance at the dose of 200 g ha-1 a.i. Using the PCR-DGGE technique allowed the distinction of two profiles of bacteria in the rhizospheric activity of C. ensiformis. The second bacterial profile formed was more efficient in decontaminating soil contaminated with sulfentrazone residue. The microbiota associated with the rhizosphere of C. ensiformis has an efficient profile in decontaminating soils with residues equivalent to 200 g ha-1 a.i. the herbicide sulfentrazone.

Phytoremediation of soils contaminated with herbicide residues is a viable technique for decontamination of the environment.Canavalia ensiformis has an efficient profile in the decontamination of soils with residue equivalent to 200 g ha⁻¹ a.i. of the herbicide sulfentrazone.The PCR technique and microbial respiration used to analyze the diversity and estimate the bacterial population of a soil are viable tools to evaluate the phytoremediation potential of the microbiota associated with plant species.

Detoxification of coir pith through refined vermicomposting engaging Eudrilus eugeniae.

Hazardous coir industrial waste, coir pith has been subjected to 50 days vermicomposting with Eudrilus eugeniae by amending nitrogenous legume plant, Gliricidia sepium together with cattle dung in different combinations, after 21 days precomposting using Pleurotus sajor-caju spawn. An increase in electrical conductivity, total NPK and calcium, and a decrease in organic matter, total organic carbon, C/N ratio, C/P ratio and total phenolic content in the final vermicompost were observed. Dehydrogenase, urease and cellulase activity peaked up to 30 days of vermicomposting and then declined. The phytotoxicity studies with Brassica juncea, C/N ratio and enzyme activities confirmed the stability and maturity of vermicompost. The results also demonstrated that the 2:3:1 ratio (coir pith + Gliricidia sepium + cow dung) is a suitable effective combination for nutrient-rich (N: 2.43%; P: 0.92%; K: 2.09%) vermicompost production. The total phenolic contents declined during the vermicomposting with a lower final content of 21.26 mg/g GAE in 2:3:1 combination of substrates from the initial level (105.56 mg/g GAE). Besides, the concentration of total phenol contents inversely related to the germination index of Brassica juncea (r = -0.761), indicating that the phenolic content could also play an important role in phytotoxicity. Growth and fecundity of Eudrilus eugeniae in 2:3:1 combination revealed the acceptability and rapid decomposition of coir pith substrate into vermifertilizer.

The effect of green fertilizers on the ecological structure of soil invertebrate communities in an andisol of Southwestern Colombia

Introduction: Chemical fertilizers for agriculture can negatively affect the communities of soil invertebrates that contribute to nutrient cycling, nutrient availability, soil formation and fertility. As an alternative, previous work has suggested that green fertilizers (fresh tissue from plants) are effective to preserve soil fertility, without affecting the ecological properties of invertebrate communities. Objective: This work aimed to evaluate how green fertilizers affect the ecological structure of an invertebrate community in an andisol from Southwestern Colombia. Methods: Fresh leaves from seven plant species locally sown and grown in March 2018 were used as the fertilizers by incorporating and mixing them with the soil in 24 experimental subplots. After 45 days of incorporation, the abundance, richness, biomass and diversity of soil invertebrates were measured in three replicate soil cores per subplot and at three depths. Results: Comparing against a control treatment with no fertilization, the richness and abundance of soil invertebrates were up to 14-fold higher in treatments with Alnus jorullensis and Brassica napus, and up to 5-fold higher in treatments with Vicia sativa, Lupinus mutabilis, Plantago lanceolata and Medicago sativa. Diversity indices showed a shift from high dominance by one or a few invertebrate families in the control treatment, to a high diversity and greater evenness in the A. jorullensis, P. lanceolata and M. sativa treatments. Biomass was negatively correlated with richness and abundance, suggesting a possible ecological trade-off worth to evaluate in further research. Conclusions: In general, our results demonstrate that the application of green fertilizers in this Andean environment can significantly improve the ecological status of soil invertebrate communities. These communities ultimately provide the ecological functions for soil dynamics; thus, agroecology practices should consider them as a valuable alternative to balance production and conservation.

Introducción: Los fertilizantes químicos para la agricultura afectan negativamente a las comunidades de invertebrados, las cuales contribuyen al ciclaje, disponibilidad de los nutrientes y a la formación y fertilidad del suelo. Como alternativa, investigaciones previas han sugerido que los abonos verdes (tejido fresco de plantas) son efectivos para conservar la fertilidad del suelo, posiblemente sin afectar los invertebrados. Objetivo: Evaluar como la aplicación de abonos verdes al suelo afecta cuantitativamente estas propiedades en una comunidad de macrofauna edáfica de un andisol al suroccidente de Colombia. Métodos: El follaje fresco de siete especies de plantas sembradas y cultivadas localmente durante marzo 2018 fue utilizado como abono verde, el cual fue incorporado y mezclado con el suelo superficial en 24 subparcelas experimentales. Después de 45 días de aplicar los abonos, se midió la abundancia, riqueza, biomasa y diversidad de la comunidad de invertebrados. Resultados: En comparación a un tratamiento testigo la riqueza y abundancia de invertebrados fue 14 veces más alta en tratamientos con A. jorullensis y B. napus, y cinco veces más alta en tratamientos con V. sativa, L. mutabilis, P. lanceolata y M. sativa. Los índices de diversidad mostraron un cambio desde una dominancia por una o pocas familias de invertebrados en el testigo, a una alta diversidad y equitatividad en los tratamientos con A. jorullensis, P. lanceolata y M. sativa. La biomasa estuvo correlacionada negativamente con la riqueza y la abundancia, sugiriendo un posible trade-off, en este sentido se sugiere que sea estudiada en futuras investigaciones. Conclusiones: En general, estos resultados demuestran que la aplicación de abonos verdes en estos suelos andinos puede mejorar significativamente la presencia de macroinvertebrados en el suelo.

Integrated network analysis reveals the importance of microbial interactions for maize growth.

Microbes play a critical role in soil global biogeochemical circulation and microbe-microbe interactions have also evoked enormous interests in recent years. Utilization of green manures can stimulate microbial activity and affect microbial composition and diversity. However, few studies focus on the microbial interactions or detect the key functional members in communities. With the advances of metagenomic technologies, network analysis has been used as a powerful tool to detect robust interactions between microbial members. Here, random matrix theory-based network analysis was used to investigate the microbial networks in response to four different green manure fertilization regimes (Vicia villosa, common vetch, milk vetch, and radish) over two growth cycles from October 2012 to September 2014. The results showed that the topological properties of microbial networks were dramatically altered by green manure fertilization. Microbial network under milk vetch amendment showed substantially more intense complexity and interactions than other fertilization systems, indicating that milk vetch provided a favorable condition for microbial interactions and niche sharing. The shift of microbial interactions could be attributed to the changes in some major soil traits and the interactions might be correlated to plant growth and production. With the stimuli of green manures, positive interactions predominated the network eventually and the network complexity was in consistency with maize productivity, which suggested that the complex soil microbial networks might benefit to plants rather than simple ones, because complex networks would hold strong the ability to cope with environment changes or suppress soil-borne pathogen infection on plants. In addition, network analyses discerned some putative keystone taxa and seven of them had directly positive interactions with maize yield, which suggested their important roles in maintaining environmental functions and in improving plant growth.

Maize growth responses to soil microbes and soil properties after fertilization with different green manures.

The use of green manures in agriculture can provide nutrients, affect soil microbial communities, and be a more sustainable management practice. The activities of soil microbes can effect crop growth, but the extent of this effect on yield remains unclear. We investigated soil bacterial communities and soil properties under four different green manure fertilization regimes (Vicia villosa, common vetch, milk vetch, and radish) and determined the effects of these regimes on maize growth. Milk vetch showed the greatest potential for improving crop productivity and increased maize yield by 31.3 %. This change might be related to changes in soil microbes and soil properties. The entire soil bacterial community and physicochemical properties differed significantly among treatments, and there were significant correlations between soil bacteria, soil properties, and maize yield. In particular, abundance of the phyla Acidobacteria and Verrucomicrobia was positively correlated with maize yield, while Proteobacteria and Chloroflexi were negatively correlated with yield. These data suggest that the variation of maize yield was related to differences in soil bacteria. The results also indicate that soil pH, alkali solution nitrogen, and available potassium were the key environmental factors shaping soil bacterial communities and determining maize yields. Both soil properties and soil microbes might be useful as indicators of soil quality and potential crop yield.

Influência da adubação verde nas propriedades físicas e biológicas do solo e na produtividade da cultura de soja / Influence of green manure in physical and biological properties of soil and productivity in the culture of soybean

A adubação verde consiste na prática de uso de espécies vegetais em rotação, sucessão ou consorciação com outras culturas comerciais, objetivando melhoria, manutenção e recuperação das propriedades físicas, química se biológicas do solo. Assim, objetivou-se avaliar a influência de diferentes adubos verdes nas características do solo e na produtividade da cultura de soja. O experimento foi realizado em Maringá (PR), em delineamento de blocos casualizados, com seis tratamentos e quatro repetições: T1: aveia branca (Avena Sativa); T2: aveia preta (Avena strigosa), T3: guandu anão (Cajanus cajan), T4: nabo forrageiro (Raphanus sativus L.), T5: tremoço branco (Lupinus albus) e T6: testemunha (pousio). Ao final do experimento foram estabelecidas relações entre o adubo verde utilizado, à produção de soja, à produção de fitomassa, ao desenvolvimento de microrganismos e densidade aparente do solo. Os dados foram analisados em programa estatístico e as médias comparadas pelo teste de Tukey a 5% de probabilidade. As coberturas que propiciaram maior teor de fitomassa foram o tremoço, a aveia preta e feijão guandu. Os tratamentos que mais influenciaram o aumento de microrganismos do solo foram o tremoço, nabo forrageiro e feijão guandu. Em relação à produtividade,maiores valores encontrados foram obtidos nos tratamentos com feijão guandu, tremoço e aveia branca.Quanto à densidade aparente do solo, o tratamento com nabo forrageiro apresentou melhor resultado.

Green manuring is the practice of using plant species in rotation, succession or intercropped with other crops, aiming improvement, maintenance and recovery of physical, chemical and biological soil properties. The objective was to evaluate the influence of different green manures on soil characteristics and productivity of soybean. The experiment was conducted in Maringá (PR) in a randomized block design with six treatments and four replications: T1: oat (Avena Sativa), T2: black oat (Avena strigosa), T3: dwarf pigeon pea (Cajanuscajan), T4: radish (Raphanus sativus L.), T5: white lupine (Lupinus albus) and T6: control (fallow). At the end of the experiment, relations were established between the green manure used for soybean production, the production of biomass, the development of microorganisms and soil bulk density. The data were analyzed with statistical software and means were compared by Tukey test at 5% probability. The coverages provided higher content of dry matter were lupine, black oat and faba bean. Treatments that most influenced the increase of soil microorganisms were lupine, radish and pigeonpea. Regarding productivity, higher values were obtained in treatments with pigeon pea, lupine and oat. The apparent density of the soil, treatment with turnip showed better results.

The effects of Brassica green manures on plant parasitic and free living nematodes used in combination with reduced rates of synthetic nematicides.

Brassica plants once incorporated into soil as green manures have recently been shown to have biofumigant properties and have the potential of controlling plant-parasitic nematodes. In Washington State, plant-parasitic nematodes are successfully managed with synthetic nematicides. However, some of the synthetic nematicides became unavailable recently or their supply is limited leaving growers with few choices to control plant-parasitic nematodes. The objective of this project was to evaluate the effects of Brassica green manures on their own and in combination with reduced rates of synthetic nematicides on plant-parasitic nematodes and free living nematodes. In a greenhouse experiment and field trials in three seasons, Brassica green manures in combination with half the recommended rate of 1,3-dichloropropene (1,3-D, Telone) reduced root knot nematode, Meloidogyne chitwoodi to below detection levels, and reduced lesion nematodes, Pratylenchus penetrans and stubby root nematodes, Paratrichodorus allius, to below economic thresholds. The combination treatments did not affect the beneficial free-living nematode populations and the non-pathogenic Pseudomonas. The total cost of growing and soil-incorporating Brassica crops as green manures in combination with reduced rates of 1,3-D was approximately 35% lower than the present commercial costs for application for the full rate of this fumigant. Integrating conventional management practices with novel techniques fosters sustainability of production systems and can increase economic benefit to producers while reducing chemical input.