Joaquín Adolfo Montes-Molina

Effect of pest-controlling neem and mata-raton on bean growth, soil N and soil CO2 emissions

Extracts of plants such as neem (Azadirachta indica A. Juss.) and mata-raton (Gliricidia sepium (Jacquin)) are used to control pests. However, certain components of neem, such as azadirachtin, can exert a negative effect on fungi and nitrifying bacteria, and, in turn, can impact the C and N cycles in soil. Nutrient cycling might thus be inhibited and affect the sustainability of an agricultural system in which plant extracts are used to control pests. Here, we investigated the effect of neem extract on microbial activity and N mineralization in soil. We studied the effect of neem and mata-raton leaf extracts on bean growth (Phaseolus vulgaris L.), nodule formation by Rhizobium, soil CO2 emissions and soil N dynamics. Four treatments were applied: (1) “neem treatment”: extracts of neem leaves, (2) “mata-raton treatment”: extracts of mata-raton, (3) “chemical treatment”: a chemical insecticide, lambda cyalothrin, and (4) “control”: untreated plants. Our results show that in non-amended soil the number of nodules in the neem treatment was 18 for beans cultivated. This nodule number was 2.1 times lower compared with the soil treated with lambda cyalothrin (chemical treatment). In manure-amended soil, the number of nodules was 28 in the neem treatment. This nodule number was 1.6 times lower than in the mata-raton treatment. This indicated that neem extracts inhibited Rhizobium in soil and nodule formation in bean. In the manure-amended soil, the emission of CO2 was 1.9 times lower in the neem-treated soil than in the other treatments. The increase in the concentration of NO3− was 1.03 mg N kg− soil day− in the neem treatment and 4.1 times lower compared with the other treatments. As such, microbial activity was inhibited by the neem extracts when added to the manure-amended soil. It was found that application of neem leaf extract inhibited microbial activity and reduced nodule formation in bean, but lambda cyalothrin or leaf extracts of Gliricidia sepium did not.

Bacterial Communities Associated with Different Anthurium andraeanum L. Plant Tissues

Plant-associated microbes have specific beneficial functions and are considered key drivers for plant health. The bacterial community structure of healthy Anthurium andraeanum L. plants was studied by 16S rRNA gene pyrosequencing associated with different plant parts and the rhizosphere. A limited number of bacterial taxa, i.e., Sinorhizobium, Fimbriimonadales, and Gammaproteobacteria HTCC2089 were enriched in the A. andraeanum rhizosphere. Endophytes were more diverse in the roots than in the shoots, whereas all shoot endophytes were found in the roots. Streptomyces, Flavobacterium succinicans, and Asteroleplasma were only found in the roots, Variovorax paradoxus only in the stem, and Fimbriimonas 97%-OTUs only in the spathe, i.e., considered specialists, while Brevibacillus, Lachnospiraceae, Pseudomonas, and Pseudomonas pseudoalcaligenes were generalist and colonized all plant parts. The anaerobic diazotrophic bacteria Lachnospiraceae, Clostridium sp., and Clostridium bifermentans colonized the shoot system. Phylotypes belonging to Pseudomonas were detected in the rhizosphere and in the substrate (an equiproportional mixture of soil, cow manure, and peat), and dominated the endosphere. Pseudomonas included nine 97%-OTUs with different patterns of distribution and phylogenetic affiliations with different species. P. pseudoalcaligenes and P. putida dominated the shoots, but were also found in the roots and rhizosphere. P. fluorescens was present in all plant parts, while P. resinovorans, P. denitrificans, P. aeruginosa, and P. stutzeri were only detected in the substrate and rhizosphere. The composition of plant-associated bacterial communities is generally considered to be suitable as an indicator of plant health.

Effects of Vermicompost and Vermiwash on Plant, Phenolic Content, and Anti-oxidant Activity of Mexican Pepperleaf (Piper auritum Kunth) Cultivated in Phosphate Rock Potting Media

ABSTRACT The aim of this investigation was to determine the effect of vermicompost, vermiwash, and phosphate rock on plant, total phenols, flavonoids, and anti-oxidant activity in Piper auritum Kunth leaves. P. auritum plants were obtained from cuttings and were planted according to the Box-Behnken experimental design with three repetitions at the central point. The factors and levels were vermicompost (10, 20, and 30 g plant−1), vermiwash (5, 10, and 15 mL plant−1), and phosphate rock (1, 2, and 3 g plant−1). Plant growth parameters (plant height, stem diameter, leaves number) and chlorophyll content were measured 1 month after treatment applications. Total phenols, total flavonoids, and 1,1-diphenyl-2-picryl-hydrazyl radical scavenging activity was measured after 4 months. Vermicompost, vermiwash, and phosphate rock had no statistically significant effect on plant growth. Plant height, stem diameter, leaves number, chlorophyll, innermost number, fresh weight stem, fresh weight leaves, fresh weight root, dry weight stem, dry weight leaves, and dry weight root were not different among treatments. Total phenolic compounds were statistically affected for both vermiwash and phosphoric rock (p < 0.05) and the anti-oxidant activity decreased by vermicompost addition. The application of 15 mL plant−1 vermiwash, 1 g phosphate rock, and 20 g vermicompost plant−1 increased the total phenol content.

Vermicomposting leachate as liquid fertilizer for the cultivation of sugarcane (Saccharum sp.)

ABSTRACT In vermicomposting, the main product is the worm casts, but a leachate is generated that contains large amounts of plant nutrients. This leachate is normally diluted to avoid plant damage. We investigated how dilution of vermicompost leachate combined with different concentrations of nitrogen (N) - phosphorus (P) - potassium (K) triple 17 fertilizer, and polyoxyethylene tridecyl alcohol as dispersant and polyethylene nonylphenol as adherent to increase efficiency of fertilizer uptake, affected sugarcane plant development. The vermicomposting leachate with pH 7.8 and electrolytic conductivity 2.6 dS m−1, contained 834 mg potassium (K) l−1, 247 mg nitrate (NO3−) l−1 and 168 mg phosphate (PO43−) l−1, was free of pathogens and resulted in a 65% germination index. Vermicompost leachate did not inhibit sugarcane growth and mixed with 170 g l−1 NPK triple 17 fertilizer resulted in the best plant development. No dispersant or adherent was required to improve plant height and stem development.

Emission of N2O from polycyclic aromatic hydrocarbons contaminated soil at different water contents added with vermicompost.

Vermicompost is typically applied to improve soil quality, but can be used to remediate hydrocarbon-contaminated soils. Little information is available on how contamination and subsequent bioremediation with vermicompost affects emissions of N2O and CO2, important greenhouse gases. A sandy loam soil with different water contents (40%, 60%, 80% and 100% of water holding capacity (WHC)) was contaminated with phenanthrene, anthracene and benzo(a)pyrene and amended with or without vermicompost to stimulate remediation of soil. Emissions of N2O and CO2, and concentrations of inorganic N (ammonium (NH4+), nitrite (NO2−) and nitrate (NO3−)) were determined in a laboratory incubation experiment after 0h, 5h, 24h, 72h and 168h. The cumulative CO2 production rate was significantly larger in soil incubated at 60%WHC and 80%WHC compared to soil incubated at 40% and 100%WHC. Addition of vermicompost increased production of CO2 and N2O. Addition of PAHs increased production of CO2 when water content of soil was at 60%WHC and production of N2O when water content of soil was at 80% WHC. Addition of PAHs induced immobilization of inorganic N and inhibited nitrification as the concentration of NH4+ and NO2− in soil contaminated with PAHs was larger than in unamended soil while the concentration of NO3− was lower. It was found that contamination of soil with PAHs increased emissions of N2O and CO2 and biostimulation of autochthonous microflora with organic material to remediate those soils further increases production of N2O and CO2. These findings indicate that trace gas emissions should be included in estimations of the environmental impact of contamination of soil and their subsequent bioremediation.

Enzymatic Activities in Soil Cultivated with Coffee (Coffea arabica L. cv. ‘Bourbon’) and Amended with Organic Material

The objective of this study was to investigate the growth of coffee (Coffea arabica L. cv. ‘Bourbon’) in soil amended with compost, vermicompost, and bokashi at 25%, 50%, and 66% while mycorrhizal colonization and activity of acid and alkaline phosphatases and urease in soil were monitored. Treatments with 25% compost as well as higher application rates of compost and bokashi (50% or 66%) increased coffee growth. Shoot fresh weight increased 5 times when 25% bokashi or compost was applied, 8 times when 50% was applied and 10 times when 66% was applied compared to the control plants without organic fertilizer. Acid and alkaline phosphatase and urease activity increased when organic fertilizer was applied to soil. Application of organic fertilizers increased the growth and fresh weight of root and shoot of coffee plants and improved the root mycorrizal colonization and enzymatic activity of the soil.

Aluminium tolerance in the tropical leguminous N2-fixing shrub Acaciella angustissima (Mill.) Britton & Rose inoculated with Sinorhizobium mexicanum

La leguminosa tropical Acaciella angustissima inoculada con o sin la cepa Sinorhizobium mexicanum ITTG R7T fue cultivada en un suelo tratado con (Al) para estudiar la tolerancia a este metal. Las plantas de A. angustissima fueron crecidas en el suelo con 0, 2, 4 y 6 mg de Al kg-1. Se hizo un seguimiento del efecto de Al e inoculacion en el crecimiento, la nodulacion, el contenido de nitrogeno y el contenido de taninos en las plantas. La altura, el peso seco total y el peso seco de la raiz de las plantas decremento significativamente cuando el suelo fue tratado con Al, pero incremento cuando fue inoculado. El Al disminuyo el numero de nodulos. El inoculo incremento el N total y el contenido de taninos de las plantas. En este experimento fue encontrado que el Al reduce el crecimiento de la leguminosa arbustiva tropical fijadora de N2 A. angustissima, mientras la inoculacion con S. mexicanum ITTG R7T estimula el crecimiento e incrementa el contenido de taninos y nitrogeno.