Vladislav Popov

Atrazine degradation in soils: the role of microbial communities, atrazine application history, and soil carbon

The degradation rate of atrazine in floodplain soils under natural grasslands and cropped fields in the Liverpool Plains, NSW, was studied under laboratory incubation and in glasshouse bioassays, and related to soil properties including microbial community analysis by t-RFLP. The experiments were part of a broader study aiming to manage pesticides in the environment using vegetative filters (biofilters). The soils differed in their atrazine treatment history. Degradation rate (half-life) in cropped soil was more rapid (≈2 to 7 days) than in 2 grassland soils (≈8 to ≈22 days). Bioassays in the glasshouse using oats and soybeans supported this finding. The t-RFLP analysis disclosed the presence of 2 consortia of bacterial species that are reported in the literature to degrade atrazine. These were: (i) Rhodococcus sp, Pseudomonas aeruginosa, and Clavibacter michiganense and (ii) Acinetobacter sp., Pseudomonas sp., and Streptomyces sp. Their dynamics during incubation suggested that they might have been responsible for the more rapid atrazine degradation in the cropped soil. The enhanced atrazine degradation in cropped soil was also associated with lower concentrations of soil organic C and percentage of light fraction carbon compared with grassland soils, suggesting that atrazine provided an additional source of N and C to organisms that can quickly degrade the herbicide. The finding of relatively short atrazine half-life has implications for the effectiveness of the herbicide, as well as for the loads of pesticide potentially entering the environment. The results suggest there is little risk of atrazine accumulating in biofilters and causing damage.

Allelopathic Effect of Dodder on Different Varieties of Lucerne and Bird’s Foot-Trefoil

Summary The aim of this study was to evaluate the allelopathic effect of cold aqueous extracts, both fresh and dry biomass of dodder (Cuscuta epithymum L.) on lucerne (Medicago sativa L.) and bird’s foot-trefoil (Lotus corniculatus L.). Four different varieties of lucerne “Pleven 6”, “Dara”, “Roly”, “Multifoliolate”) and bird’s foot-trefoil (“Gran San Gabriele”, “Leo”, “Local population 1”, “Local population 2”) were studied in order to find some varieties with allelopathic tolerance. Ex-situ experiment was carried out as follows: 100 seeds of each variety were put in Petri dishes between filter paper, both cold extracts of parasitic weed biomass were pipetted at a ratio of 1:20 as against the seed mass and then were placed in a thermostat-operated device at a temperature of 22 ± 2°С. Distilled water was used as a control. Percentage inhibition, Index of tolerance and Index of plant development were calculated for assessment of the allelopathic effect of dodder on the early seedling growth, biomass synthesis and initial development of experimental varieties. As a whole, dry weed biomass was found as more toxic for the tested plants than the fresh one. Medicago sativa var. multifoliolate and Lotus corniculatus var. Local population 1 and Local population 2 showed a significant tolerance to the allelopathic influence of Cuscuta epithymum in all studied concentrations of aqueous extract of fresh weed biomass (25, 50 and 100 g l−1) and medium tolerance to aqueous extract of dry weed biomass (concentrations of 25 and 50 g l−1).

Adaptive technology of environmentally - friendly production of legumes in the dry steppe zones

Modern agronomic technologies must include environmentally- friendly technologies in crop growing. In Kazakhstan, despite its significant potential, environmentallyfriendly farming is underdeveloped with little scientific backing. Therefore, the objectives of this study were to develop and suggest an adaptive technology for cultivation of legumes taking into account existing methodologies for environmentallyfriendly production in the dry steppe zone of Akmola region, Northern Kazakhstan. In order to achieve the objectives, the study focused on determination of a complex impact of combination of agroecological conditions (incl. agro- climatic, content of selected heavy metals such as Cu and Zn in soil, weed pressure, etc.), contrasting soil cultivation technology (i.e. traditional vs zero- tillage), nutrient inputs (fertilizers, legume stimulators) and pesticides on growth and productivity of selected legume crops (peas and chickpeas). The overall agroecological and growing conditions were suitable for producing economically- important legume crops (i.e. pea and chickpea), despite the temperature fluctiations and soil moisture shortage. Despite the very low content of N and P in the upper soil layer, the Cu and Zn content was within the Maximum Permissible Limits (MPL) for Kazakhstan, with a low anticipated negative effect on target legume growth. The least number of weeds was recorded by the variant with application of biological preparation Respecta. The targeted legumes were better developed during the growing season under the traditional technology compared to zero- tillage technology, i.e. germination and seed viability, which might be attributed to better utilisation of soil air and improved soil porosity of the soil layer of 0- 20 cm when using traditional technology. Combinations of mineral fertilizer CaSO4 + 2H2O5 with the innoculation promoter Rizotorfin, and Izagry Phosphorus with Rizotorfin may be recommended to farmers. The application of plant inoculation promoter Rizotorfin was more effective when combined with Phosphorus promoter Izagry Phosphorus. This combination i) reduced the time of passing the main phenophases of pea and chickpea, and the overall length of vegetation (in days). It gives farmers an opportunity to apply late sowing, e.g. in the beginning of June and use the higher temperatures during main vegetation period, and ii) had a positive impact on biological productivity of peas and chickpeas, i.e. an increase with percentage compared to control variant. The results have shown that seed inoculation with Rizotorfin (containg Rhizobium bacteria) and additional Phosphorus fertilizers would lead to significant increase of plant productivity, i.e. yield in the conditions of dry climate in Northern Kazakhstan.

Impact of biofertilisers and agrometeorological conditions on phenological growth of pepper (Capsicum annuum L.) in organic agriculture

The pepper has a relatively large share in the general structure of the vegetable production in Bulgaria. The objective of this research was to investigate the influence of biofertiliser Emosan (HemoZym NK, Hemozym Bio N5) in combination with biofertilisers Lumbrical and Boneprot, as well as the influence of certain agrometeorological conditions on the phenological growth of pepper cv. ‘Sofiiska Kapiya’. This experiment was carried out in 2009 – 2011 on the experimental fields ofthe Agroecological Centre at the Agricultural University Plovdiv (Bulgaria). The pepper was grown using existing technology for mid-early field production, according to the principles of organic agriculture. The agroclimatic characteristics were taken on the basis of data of twenty-four-hour performance of meteorological factors. In thethree years of the experiment the temperature conditions during the period of active vegetation of the pepper (June - July - August) were above the average, which was in conjunction with the global trends. The application of biofertiliser Emosan, in combination with basic fertilization with biofertilisers Boneprot and Lumbrical and under the impact of suitable agrometeorological conditions, had a positive impact on the pepper plants. Pepper plants showed earlier entry into the main phenophases under field conditions of organic farming.