A Physiological behavior and tolerance of Lactuca sativa to lead nitrate and silver nitrate heavy metals

This study goal to evaluate the effects of different concentrations of lead (Pb) and silver (Ag) on germination, initial growth and anatomical alterations of Lactuca sativa L. Plants use various mechanisms to reduce the impacts caused by anthropic action, such as xenobiotic elements of soils and water contaminated by heavy metals. These metals were supplied as lead nitrate and silver nitrate and the following treatments were established: control for both metals, maximum dose of heavy metals, for arable soils, allowed by the National Council of the Environment (Ag = 25 mg. Kg-1, Pb = 180 mg. Kg-1), double (Ag = 50 mg. Kg-1, Pb = 360 mg. Kg-1) and triple (Ag = 75 mg. Kg-1, Pb = 540 mg. Kg -1) of this dosage. Vigor and germination tests of the seeds and possible anatomical changes in the leaves and roots of lettuce plants were performed. The species showed a high capacity to germinate under Pb and Ag stress, and the germination was never completely inhibited; however, the germination decreased with increasing Pb concentrations, but not under Ag stress. The use of increasing doses of metals reduced seed vigor and increased chlorophyll content. An increase in biomass was also observed in plants from treatments submitted to Pb. The phytotoxic effects of metals were more pronounced at 15 days after sowing. Anatomically, L. sativa was influenced by metal concentrations, and had a reduction of up to 79.9% in root epidermis thickness at the highest Pb concentration, although some structures did not suffer significant changes. The results suggest that L. sativa presents tolerance to high concentrations of heavy metals, showing possible mechanisms to overcome the stress caused by these metals. In this research lettuce possibly used the mechanism of exclusion of metals retaining Pb and Ag in the roots preserving the photosynthetic apparatus in the aerial part of the plants. In general, the chemical element Pb was more toxic than Ag, in these experimental conditions.

The main results of monitoring the fertility of arable soils in the forest-steppe zone of the Central Chernozem Region (on the example of the Belgorod)

The paper analyzes the results of an agrochemical survey for 2010-2019 of arable soils of the Ivnyansky district of the Belgorod region, located in the south-west of the forest-steppe zone of the Central Chernozem region (CDR). It was found that in the soil and climatic conditions of this area for the period from 2010-2014 to 2015-2019. a decrease in the doses of applied mineral fertilizers from 126.6 to 122.8 kg/ha and a simultaneous increase in the doses of organic fertilizers from 18.3 to 23.1 t/ha contributed to an increase in the yield of winter wheat by 28.3%, spring barley - by 22.7%, corn for grain - by 24.7%, sugar beet - by 34.8%, sunflower - by 26.6% and soybeans - by 15.2%. At the same time, the content of mobile forms of phosphorus in soils increased by 29, potassium - by 53, sulfur - by 0.20, copper - by 0.51, manganese - by 3.61, cobalt - by 0.007 mg/kg, organic matter - by 0.25%. As a result of the implementation of measures for chemical reclamation of acidic soils on an area of 29.6 thousand hectares, the proportion of acidic soils decreased from 80.0 to 56.2%. Keywords: RECLAMATION, TRACE ELEMENTS, ORGANIC MATTER, PHOSPHORUS, POTASSIUM, FERTILIZERS, CHERNOZEM, FERTILITY, ACIDITY

Soil biotest results using Azotobacter bacteria: interpretation problems and possible solutions

The aim of the study. The Azotobacter genus is a well-known bioassay for testing the soil environment quality. A large number of these bacteria is considered as evidence of the ecological well-being of a soil. However, a high number of these microorganisms was found in disturbed ecosystems, which means there is a problem of how to interpret the results of the biotest. Therefore the aim of the study was to clarify the causes of this problem and suggest a possible way to solve it. Location and objects of the study. The study was conducted in West Siberia (Russia) in the Priobskoe plateau (54°53'13.5"N, 82°59'36.7E"). Leached сhernozem with different content of organic matter (mortmass) was studied under the following treatments: 1) permanent fallow, 2) wheat cultivation, annual removal of straw from the field + summer fallow, 3) wheat + left straw + summer fallow, 4) wheat +left straw + green manure fallow, 5) grassland. The content of N-NO3, respectively, was equal to 50, 10, 15, 5, 0 mg/kg. Another object was a site at the mining and processing plant "Denisovsky" in South Yakutia (Russia) (56°46'20.23"N, 124°51'06.95"E). Abandoned for a long time (30 years) after coal mining spoils were studied in two variants: without plants and with well-developed vegetation cover. Total SOC content was 1.8 and 5.7%, N – 0.3 and 0.4 %, respectively. Methodology. The direct sowing of single soil aggregates onto the N-free medium containing glucose as C-source was used to cultivate Azotobacter. Glucose (10 mg/g soil) was added to the soil to activate Azotobacter growth. A live culture of bacteria was introduced into the soil at a dose of 1 ml/g to check the viability of Azotobacter in experimental soils. Main results. The status of the microbial community in situ was observed on microbial landscapes obtained by exposing slides in the undisturbed soil for 30 days. The overgrowth of soil lumps in the specified range of options was 0–80–40–0–0% and after glucose addition – 100–80–80–0%. The activation of Azotobacter growth after glucose addition was inversely proportional to the C: N ratio (between the mortmass and the mineral nitrogen). Live Azotobacter culture under grassland developed 2.5 times slower in comparison with the fallow. Similar patterns were found in the study of the soils developed on the coal mining spoils. Activation of Azotobacter growth by glucose (response to stress) was more pronounced in soils with apparently less favorable environment for bacteria. Conclusion. The reason behind misleading interpretation of Azotobacter biotest results was that the original purpose of the test was to assess fertility of arable soils. This role of the indicator bacterium was previously underestimated. It is known that the arable soil belongs to the category of disturbed ones, and the abundance of Azotobacter may indicate instability in the microbial community of the soil. To expand the capabilities of the biotest, the authors propose to supplement the test with a procedure for evaluating the Azotobacter growth response to experimental stress, e.g. C-substrate addition.

Microbial Diversity and P Content Changes after the Application of Sewage Sludge and Glyphosate to Soil

Pesticides, despite their side effects, are still being used in almost every agriculture, horticulture, maintaining municipal greenery in urban areas and even in home gardens. They influence human life and health and the functioning of entire ecosystems, including inanimate elements such as water and soil. The aim of the study was the evaluation of the suitability of sewage sludge in improving the quality of soil treated with a non-selective herbicide-glyphosate, applied as Roundup 360 SL. A pot experiment was conducted with the use of two arable soils (MS and OS), which were amended with sewage sludge (SS), glyphosate (GL) and sewage sludge with glyphosate (SS+GL). Soil samples were taken after 24 h, 144 h and 240 h and total phosphorus (TP) content (TP), total number of bacteria/fungi, activity of dehydrogenases (Dha), acidic phosphatase (Acp), alkaline phosphatase (Alp), genetic biodiversity of bacteria/fungi using the terminal restriction fragment length polymorphism method were determined. The application of SS and GL to OS caused an increase in Acp (approximately 35%) and a decrease in Alp activity (approximately 20%). Additionally, GL may influence on an increase in the number of fungi and the decrease in the number of bacteria. In soil with SS+GL increase in the fungal diversity in MS and OS was also observed. Moreover, a positive between TP and the number of bacteria and the activity of phosphatases correlation was reported. The obtained results indicate that analyzed sewage sludge could be potentially applied into soil in in situ scale and could constitute a valuable reclamation material.