Azotobakterīna lietošanas efektivitāte sintētiskā slāpekļa aizvietošanā ziemas kviešos = The effectiveness of Azotobacterin in replacing synthetic nitrogen in winter wheat

The Institute of Agricultural Resources and Economics assessed the effectiveness of the use of Azotobacterin under specific agro-ecological conditions. The research was conducted in four state planning regions — Vidzeme, Latgale, Kurzeme, and Riga. The aim of the study was to determine whether the partial replacement of synthetic nitrogen (N) fertilizer with a microbiological preparation that promotes nitrogen fixation from the air could ensure an equivalent yield for winter wheat. The trials were established in soil conditions typical of the regions, characterized by good organic matter content and adequate potassium and phosphorus supply. Winter wheat ’Skagen’ was sown in 15 m⁻² plots, arranged randomly in four replications, with a sowing rate of 500 germinable seeds per square meter. Five variants were compared, with total N supply ranging from 160 to 220 kg N per hectare. In the tested variants, a portion of the nitrogen (up to 50 kg N ha⁻¹) was replaced with an equivalent dose of Azotobacterin. As a control, the traditional fertilization scheme used in the region — without microbiological preparation — was applied. In the first year of trials, it was observed that applying Azotobacterin by spraying winter wheat fields during sowing enhanced plant development. On average, over two years and across all trial sites, the variants treated with Azotobacterin had a significantly higher number of overwintering plants compared to the control (p<0.05). Yield differences among variants, compared to the control, ranged from a decrease at N160 (−0.62 t ha⁻¹) to an increase at N200 (+0.94 t ha⁻¹). The average results varied by region, highlighting the significant influence of agro-ecological factors. By summarizing the data from both years, the study confirmed that by reducing the application rate of synthetic nitrogen fertilizer and partially replacing it with the microbiological preparation Azotobacterin, which contains Azotobacter sp. and promotes biological nitrogen fixation from the atmosphere, it is possible to achieve a yield level comparable to that obtained with the full dose of synthetic nitrogen.