[0-9]{4} https://revistaschilenas.uchile.cl/handle/2250/42586 2026-05-10T18:20:55Z 2026-05-10T18:20:55Z https://revistaschilenas.uchile.cl/handle/2250/242362 2024-05-02T18:50:34Z

Study of biomass accumulation using different nutrient media In recent years, the use of microorganisms to stimulate plant growth and resistance, including biocontrol and maintenance or improvement of microbial activity and soil functionality, has increased. The aim of this work was to select nutrient media and to optimize the deep cultivation regimes of a biopreparation consisting of the Bacillus pumilus Pol P3(1) 10 B-RKM 0528, Bacillus thuringiensis Pb 30 B-RKM 0341, Bacillus licheniformis 356 B-RKM 0074 and Serratia marcescens Sh-2 B-RKM 0952 strains, which exhibit high growth-stimulating activity. Three different media were use to cultivate the biopreparation: standard meat-peptone broth medium, King's medium and Mueller-Hinton's medium. The main criterion for determining the effectiveness of the nutrient medium was the accumulation of specific components to yield the largest biomass of biopreparation cells. A comparative analysis of growth on the nutrient media was used to assess the viability and biomass accumulation of the biopreparation strains tested. The optimum cultivation period, maximum optical density of biomass growth, viability and optimum medium acidity during bacterial cultivation on nutrient media were determined both for the strains individually and as part of the biopreparation.

https://revistaschilenas.uchile.cl/handle/2250/242361 2024-05-02T18:50:26Z

How does the neighborhood of annual or perennial species affect the first one hundred days of the establishment of grasses? Pastures that include annual and perennial grasses can play a strategic role in increasing the sustainability of temperate livestock systems. However, the impacts of the competition between annual and perennial genetically improved forage species on pastures has scarcely been studied. We evaluated the early dynamics of tillering, carbon partitioning and both intra- and interspecific competition in – or between – an annual (Bromus willdenowii; prairie grass; Bw) and a perennial (Dactylis glomerata; orchard grass; Dg) C3 grass species. We sowed 24 0.18 m2 microplots in May 2008. Each microplot constituted an experimental unit and contained five sowing lines spaced 0.175 m apart. On three of the lines, we sowed different combinations of the mentioned grasses, while on the two lines between them, we sowed red clover (Trifolium pratense). We randomly applied a factorial array of eight treatments—2 species (Dg vs. Bw) × 2 types of competition (intra vs. interspecific) × 2 levels of winter nitrogen fertilization (0 vs. 170 kg of N ha-1)—designed in three complete random blocks. Fertilization did not have any significant effect on any species. The evaluation period lasted 109 days after sowing (das), separated into three phases (0-53 das, 59-90 das and 90-109 das). The variables recorded were aerial biomass (leaves, sheets and senescent material), root biomass and tiller density per species. As expected, annual Bw inhibited the growth of perennial Dg at the latest stage of establishment but surprisingly promoted it at the earliest stage. This work suggested that a low initial density of an annual species should optimize the initial facilitating effect of the annual species on the perennial species with its subsequent inhibitory effect.

https://revistaschilenas.uchile.cl/handle/2250/242360 2024-05-02T18:50:13Z

Arbuscular mycorrhizal fungi and phosphorus affect Araucaria angustifolia seedling growth Symbioses between plants and arbuscular mycorrhizal fungi (AMF) provide many advantages, including a reduced need for fertilization. In this study, the effects of AMF inoculation and phosphorus application on the growth and nutritional status of Araucaria angustifolia seedlings were evaluated. The treatments included inoculation with AMF (Gigaspora margarita, Rhizophagus intraradices, Acaulospora colombiana, Acaulospora scrobiculata, or Dentiscutata heterogama), inoculation with a mixture of AMF in 100 g of 50-year-old araucaria forest soil, application of two doses of P2O5 (25 or 100 mg kg-1), and the control. A completely randomized design was used, with seven replicates per treatment. The growth parameters, macronutrient and micro-nutrient contents, root colonization, and mycorrhizal effects on the extracted nutrients were evaluated at 75 and 150 d post germination. Analysis of variance, correlations, and principal component analysis (PCA) were used to evaluate that data. Inoculation with AMF had favorable effects on growth parameters, root colonization, and the extraction of macronutrients and micro-nutrients. In particular, the mixture of AMF from the 50-year-old araucaria forest soil, R. intraradices, and A. colombiana were beneficial. Similarly, the application of 25 mg of P2O5 significantly affected the growth of A. angustifolia seedlings compared to other treatments and increased the efficiency of root colonization.

https://revistaschilenas.uchile.cl/handle/2250/242359 2024-05-02T18:49:58Z

Impact of the Mednogorsk copper smelter on human health and soil environmental quality in Orenburg Region, Russia Nonferrous metal smelting operations are a recognized source of metal accumulation in surrounding soils. In Mednogorsk, Russia, soil contamination results from atmospheric emissions from a local copper (Cu) smelter. This study aimed to assess health risks by analyzing the levels of Cu, arsenic (As), cadmium (Cd), lead (Pb), and zinc (Zn) in 20 Mednogorsk topsoil samples and three background area samples. The phytotoxicity of metals to Lolium perenne was also evaluated. The soil ingestion protocol of the US Environmental Protection Agency was used for health risk assessment. Phytotoxicity tests were performed on ryegrass using a standard protocol. The levels of Cu correlated with those of other elements, indicating that the smelter was the source. Of concern, the carcinogenic risk exceeded the 10-04 threshold in 85% and 15% of the samples for children under five years of age and adults, respectively. In addition, 60% of the samples exceeded the safe Pb threshold for children's health (80 mg kg-1). These risk levels are unacceptable and require specific intervention by the relevant authorities. However, only 20% of the samples showed high phytotoxicity, mostly in acidic soils (pH<4.0). This discussion focuses on the potential of soil phytostabilization to reduce human metal exposure, as the results provide valuable insights for managing metal pollution in regions affected by nonferrous smelter emissions worldwide.