ABSTRACT
Field studies with the large-stemmed plant Artemisia dubia (A. dubia) have been carried out at the Vezaiciai Branch of LAMMC since 2018. According to three years of experimental results, annual dry matter (DM) yield varied from 7.94 to 10.14 t ha-1. Growing conditions, nitrogen application level, and harvesting time had statistically significant impacts on A. dubia productivity. The most important tasks of this article were to investigate and determine the factors influencing A. dubia plant biomass productivity and the evaluation of technological, power, and environmental parameters of plant biomass utilization for energy conversion and the production of high-quality solid biofuel pellets. For the experiments, six variants of A. dubia samples were used, which were grown in 2021. Plants were cut three times and two fertilization options were used: (1) no fertilization and (2) fertilization with 180 kg ha-1 of nitrogen fertilizer. These harvested plants were chopped, milled, and pressed into pellets. The physical-mechanical characteristics (moisture content, density, and strength) of the A. dubia pellets were investigated. During this study, it was found that the density in the dry mass (DM) of the pellets ranged from 1119.86 to 1192.44 kg m-3. The pellet moisture content ranged from 8.80 to 10.49%. After testing pellet strength, it was found that the pellets which were made from plant biomass PK-1-1 (first harvest without N fertilization) were the most resistant to compression, and they withstood 560.36 N of pressure. The dry fuel lower heating value (LHV) of the pellets was sufficiently high and was very close to that of the pine sawdust pellets; it varied from 17.46 ± 0.25 MJ kg-1 to 18.14 ± 0.28 MJ kg-1. The ash content of the burned pellets ranged from 3.62 ± 0.02% to 6.47 ± 0.09%. Emissions of harmful pollutants-CO2, CO, NOx, and unburnt hydrocarbons (CxHy)-did not exceed the maximum permissible levels. Summarizing the results for the investigated properties of the combustion and emissions of the A. dubia pellets, it can be concluded that this biofuel can be used for the production of pressed biofuel, and it is characterized by sufficiently high quality, efficient combustion, and permissible emissions to the environment.
ABSTRACT
With the increasing importance of energy crops, research on potential energy crops is carried out to identify plant species with high productivity and energy value. The field experiment with the new promising energy crop, Artemisia dubia (wormwood), was executed at the Vezaiciai Branch of the LAMMC. The soil site was naturally acidic Retisol (pH 4.2-4.4). The species was investigated as an energy crop through the evaluation of its biomass productivity and some energetical qualities. According to the three investigation years, DM yield significantly varied depending on the growing season, cutting time and nitrogen rate. The highest average DM yield was observed in 2020-10.58 t ha-1. On average, the DM yield varied from 6.49 t ha-1 (first cutting) to 11.82 t ha-1 (third cutting). The DM yield was positively correlated with stem height and the mass of one stem. Nitrogen use efficiency (NUE) depended on the growing season, cutting time and nitrogen rate. Both N90 and N180 rates should be used for A. dubia fertilization. Energy growing analysis (including direct and indirect expenses) revealed that the highest share of energy expenses are due to indirect energy expenses (particularly nitrogen application). EUE (energy utilization efficiency) tends to decrease as a result of increasing nitrogen fertilization. Overall, A. dubia granules are characterized by a high calorific value.
ABSTRACT
For the prevention of hilly soils from erosion, a smart selection of crop rotations is very important. The aim of this study was to investigate the influence of different agrophytocenoses on seed numbers in the soil runoff sediments and soil seed banks' relations to soil properties in hilly landscapes. This study analyzes long-term monitoring data from three different agrophytocenoses (permanent grassland, cereal-grass crop rotation and crop rotation with a row crop) set up on slopes of 9-11° steepness with collectors for soil and water installed. The soil of the southern exposition slope was a slightly eroded Eutric Retisol. In the soil of permanent grassland, the number of seeds was 4036 seeds m-2, 6.0 and 3.2 times smaller compared to cereal-grass crop rotation and crop rotation with a row crop. The seeds found in the soil runoff sediments composed, on average, 0.9% of the soil seed bank, and the number of seeds depended on the number of days with heavy precipitation during the plant vegetation period, as well as on the plant communities grown in a particular rotation. Correlation analysis showed the seed numbers' dependence on the soil's chemical and physical properties. Hill slopes were not affected by water erosion, when agrophytocenoses were based on perennial grassland and also cereal-grass crop rotation, where reduced soil tillage was applied.
