A strain of Bacillus subtilis stimulates sunflower growth (Helianthus annuus L.) temporarily

Preliminary studies showed that a Bacillus subtilis strain stimulates plant growth. We investigated how inoculating seeds of a sunflower cultivar (Helianthus annuus L.) with this strain stimulated plant growth, soil properties and emissions of greenhouse gasses, i.e. carbon dioxide (CO₂) and nitrous oxide (N₂O), when cultivated in a greenhouse. Unfertilized sunflowers or fertilized with urea served as controls. After one month, root length and fresh and dry root weight of the sunflower was significantly higher in the bacteria amended plant than in the urea and unfertilized plants. However, at harvest, no positive effect was observed. The number of seeds per plant and seed weight was not significantly different between the treatments, but total plant N was significantly higher in urea-amended plants than in unfertilized plants. The CO₂ production rate was not affected by treatment, but the N₂O emission rate was significantly higher in soil amended with urea plus bacteria soil compared to the unfertilized treatments. It was found that the B. subtilis strain used in this study had a positive, but only temporarily effect on growth of the sunflower cultivar used.     

Dynamics of carbon and nitrogen in an extreme alkaline saline soil: A review

The soil of the former lake Texcoco is an ‘extreme’ alkaline saline soil with pH > 10 and electrolytic conductivity (EC) > 150 dS m⁻¹. These conditions have created a unique environment. Application of wastewater sludge to Texcoco soil showed that large amounts of NH₄⁺ were immobilized, NO₃⁻ was reduced aerobically, NO₂⁻ was formed and the mineralization of the organic material in the sludge was inhibited. A series of experiments were initiated to study the processes that inhibited the decomposition of organic material and affected the dynamics of mineral N. The large EC and pH inhibited the decomposition of easily decomposable organic material such as glucose and maize, although cellulolytic activity was observed in soil with pH 9.8 and EC 32.7 dS m⁻¹. The high soil pH favoured NH₃ volatilization of approximately 50 mg N kg⁻¹ soil within a day and a similar amount could be fixed on the soil matrix due to the dispersed minerals and their volcanic origin. Soil microorganisms immobilized large amounts of NH₄⁺ within a day when glucose was added to soil in excess of what was required for metabolic activity. Removal of NO₃⁻ from soil amended with glucose was not inhibited by 100% O₂ and NH₄⁺ indicating that the contribution of denitrification and assimilatory reduction to the reduction of NO₃⁻ was minimal while the formation of NO₂⁻ was not inhibited by 0.1% acetylene, known to inhibit nitrification. Additionally, the reduction of NO₃⁻ in the glucose-amended alkaline saline Texcoco soil was followed by an increase in the amount of NH₄⁺, which could not be due to denitrification. It was concluded that the reduction of NO₃⁻ and the formation of NO₂⁻ and NH₄⁺ in the glucose-amended soil was a result of aerobic NO₃⁻ reduction. A phylogenetic analysis of the archaeal community in the soil of the former lake Texcoco showed that some of the clones identified were capable of reducing NO₃⁻ aerobically to NO₂⁻ when glucose was added. A study of the diversity of the bacterial dissimilatory and respiratory nitrate-reducing communities indicated that bacteria could have contributed to the process.     

Solar wind origin in coronal funnels

The origin of the solar wind in solar coronal holes has long been unclear. We establish that the solar wind starts flowing out of the corona at heights above the photosphere between 5 megameters and 20 megameters in magnetic funnels. This result is obtained by a correlation of the Doppler-velocity and radiance maps of spectral lines emitted by various ions with the force-free magnetic field as extrapolated from photospheric magnetograms to different altitudes. Specifically, we find that Ne7+ ions mostly radiate around 20 megameters, where they have outflow speeds of about 10 kilometers per second, whereas C3+ ions with no average flow speed mainly radiate around 5 megameters. Based on these results, a model for understanding the solar wind origin is suggested.     

Production of carbon dioxide and nitrous oxide in alkaline saline soil of Texcoco at different water contents amended with urea: A laboratory study

Soil of the former lake Texcoco is alkaline saline with pH often >10 and electrolytic conductivity (EC) >70 dS m^?1 with rapidly changing water contents. Little is known how fertilizing this area with urea to vegetate the soil would affect emissions of carbon dioxide (CO₂) and dynamics of N. Texcoco soil with electrolytic conductivity (EC) 2.3 dS m^?1 and pH 8.5 (TEXCOCO A soil), EC 2.0 dS m^?1 and pH 9.0 (TEXCOCO B soil) and 200 dS m^?1 and pH 11.2 (TEXCOCO C soil) was amended with or without urea and incubated at 40% of water holding capacity (WHC), 60% WHC, 80% WHC and 100% WHC, while emissions of nitrous oxide (N₂O) and CO₂ and dynamics of ammonium (NH₄⁺), nitrite (NO₂^?) and nitrate (NO₃^?) were monitored for 7 days. An agricultural soil served as control (ACOLMAN soil). The emission of CO₂ increased in the urea amended soil 1.5 times compared to the unamended soil, it was inhibited in TEXCOCO C soil and was >1.2 larger in soil incubated at 40%, 60% and 80% WHC compared to soil incubated at 100% WHC. The emission of N₂O increased in soil added with urea compared to the unamended soil, was similar in TEXCOCO A and B soils, but was <0.2 mg N kg^?1 soil day^?1 in TEXCOCO C soil and generally larger in soil incubated at 60% and 80% WHC compared to soil incubated at 40% and 100% WHC. The water content of the soil had no significant effect on the mean concentration of NH₄⁺, but addition of urea increased it in all soils. The concentration of NO₂^? was not affected by the water content and the addition of urea except in TEXCOCO A soil where it increased to values ranging between 20 and 40 mg N kg^?1. The concentration of NO₃^? increased in the ACOLMAN, TEXCOCO A and TEXCOCO B soil amended with urea compared to the unamended soil, but not in the TEXCOCO C soil. It decreased with increased water content, but not in TEXCOCO C soil. It was found that the differences in soil characteristics, i.e. soil organic matter content, pH and EC between the soils had a profound effect on soil processes, but even small changes affected the dynamics of C and N in soil amended with urea.     

Removal of Anthracene from Recently Contaminated and Aged Soils

Water, Air, &; Soil Pollution - Suspended microplastic and black carbon (BC) particles were determined in surface waters of the Jade system, southern North Sea, including freshwater sources. On...     

Is nitrate reduction to nitrite possible in glucose-amended alkaline saline soil under aerobic conditions?

A phylogenetic analysis of the archaeal community in the soil of the former Lake Texcoco showed that some of the clones identified were affiliated to Archeae that reduce nitrate (NO₃^?) to nitrite (NO₂^?) and NO₂^? to unknown products under aerobic conditions. Previous research suggested that this indeed might occur when an easily decomposable C-substrate is available, but little is known about the factors that control the possible processes involved. The sandy clay loam soil with pH 10 and electrolytic conductivity 56 dS m^?1 was spiked with 1000 mg glucose-C kg^?1 soil (GLUCOSE pre-treatment), 200 mg NO₃^?-N kg^?1 soil (NITRATE pre-treatment), or left unamended (CONTROL pre-treatment) and conditioned for eight days. Pre-treated soil was then added with 1000 mg glucose-C kg^?1 soil and 200 mg NO₃^?-N kg^?1 soil and amended with ammonium (NH₄⁺) (AMM treatment) and l-glutamine (GLUT treatment), acetylene (C₂H₂) (ACE treatment), oxygen (O₂) (OXI treatment), left untreated (CON treatment) or sterilized. No abiotic factors affected concentrations of NH₄⁺, NO₂^? or NO₃^?. In the CONTROL pre-treatment, concentration of NO₃^? decreased 170 mg N kg^?1 soil within 72 h, in the GLUCOSE pre-treatment with 182 mg N kg^?1 soil within 2 h and in the NITRATE pre-treatment with 272 mg N kg^?1 soil within 168 h. Mean concentration of NO₂^? was 3.2 mg N kg^?1 soil in unamended soil, 5.7 mg N kg^?1 soil in the CONTROL pre-treatment, but >20 mg kg^?1 soil in the GLUCOSE pre-treatment and ≥40 mg kg^?1 in the NITRATE pre-treatment. The application of NO₃^? and glucose increased the mean concentration of NH₄⁺ compared to the unamended soil independently of pre-treatment. It was found that microorganisms in the alkaline saline soil of the former Lake Texcoco can reduce concentrations of NO₃^? while releasing NO₂^? under aerobic conditions when an easy decomposable substrate is available without it being directly related to microbial activity and this being more outspoken when glucose or nitrate were previously added.