Due to the variability of soil characteristics in the field and the rising prices of high-quality seeds, farmers are increasingly interested in applying a system of precision variable rate seeding (VRS), which makes it easier to manage risks in crop production and allows to ensure the profitability of the farm. Most modern seed drills are equipped with a hydraulic or electric drive and a terminal in the tractor cabin, allowing farmers to apply VRS. The aim of this study was to determine the most appropriate seeding rate of winter wheat according to the measured apparent soil electrical conductivity (ECa) in the field, to investigate the uniformity of seed placement by layers in the soil and to evaluate the germination dynamics of winter wheat. Precision seeding was performed using a VRS map, generated from soil ECa data obtained by field surface scanning using the ECa device EM-38 MK2. Winter wheat seeding was implemented with a direct seed drill. The research was carried out by measuring the parameters of winter wheat seedbed and germinated plants, including the number and distribution of seeds in soil layers of different depths, germination, tillering. Field research was performed with 3 treatments and 4 repetitions (1uniform rate seeding; 2 -VRS; 3 -VRS + variable rate fertilisation (VRF)). The results of the research showed a direct relationship between the soil ECa and the depth of seed placement. Most seeds were inserted at medium depths (15-30 mm), except in the soil management zone, where ECa was highest (28.8 mS•m -1 ). In this area, most seeds (50.7%) were inserted shallowly up to 15 mm. The experimental results of seeding studies showed that using the VRS and VRS + VRF methods in all soil zones the germination of winter wheat was similar, while seeding at the uniform rate yielded significant differences between individual soil zones.

The heavy use of mineral fertilizers causes imbalances in the biological processes that take place in soil. Therefore, it is necessary to develop more effective fertilizers or fertilizer complexes that ensure agricultural productivity and soil conservation. There is currently a lack of knowledge regarding the effectiveness of biologically enriched, complex mineral fertilizers for spring barley fertilization. The hypothesis of this study was that bacteria-enriched (Paenibacillus azotofixans, Bacillus megaterium, Bacillus mucilaginosus, and Bacillus mycoides), complex mineral fertilizers (N5P20.5K36) have significant impacts on the yield and potential for economic use of spring barley. Experimental studies were carried out for three years (2020–2022) with sandy loam soil in southern Lithuania. Four different spring barley fertilization scenarios (SCs) were investigated. In SC-1 (control), complex mineral fertilizer (N5P20.5K36) was not applied. In the other SCs, spring barley was sown with a drill and fertilizers were incorporated locally during the sowing operation: fertilization scenario SC-2 used 300 kg ha−1, SC-3 used 150 kg ha−1 preceded by a bacteria-inoculated complex mineral fertilizer (N5P20.5K36), and SC-4 used 300 kg ha−1 with the same bacterial complex. The results showed that the bacterial inoculant increased the efficiency of the mineral fertilizer and had an effect on plant growth in barley. For three consecutive years in the same plots, the bacterial inoculant showed significant positive effects on grain yield (changes of 8.1% in 2020, 6.8% in 2021, and 17.3% in 2022 between SC-2 and SC-4). Comparing the several different fertilizer scenarios from an economic point of view, it was observed that the highest profit per hectare was obtained with SC-4 in all three years of the study. Comparing SC-4 and SC-2, an increase of 13.7% was observed in 2020, followed by 9.1% and 41.9% in 2021 and in 2022, respectively. This study will be useful for farmers, biological inoculant manufacturers, and scientists researching the effectiveness of biological inoculants for growing agricultural crops. We found that it is possible to increase the yield of barley (7–17%) using the same rate of mineral fertilization by enriching it with bacterial inoculants. Further studies should be conducted to determine the effects of the bacterial inoculant on crop yield and soil over a period longer than 3 years.

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