Elements of sustainable organic soybean cultivation technology without the use of synthetic fertilizers and pesticides

The article presents the results of an experimental studies aimed at improving the technology of organic soybean cultivation through the application of biological preparations, namely the inoculant «RIZOLINE-r» (based on Bradyrhizobium japonicum strains) and plant biostimulant «KALNINI». The aim of the study was to determine the effect of biological techniques on the morphogenesis, symbiotic efficiency, photosynthetic potential and biochemical parameters of soybean grain. The studies were conducted in 2024–2025 in controlled greenhouse conditions at the AgriHortS Institute of Latvia University of Life Sciences and Technologies. The study involved three soybean varieties («Laulema», «Paradi», «Tiguan»), two inoculation schemes (control and treatment with «RIZOLINE-r» at a rate of 3 l/t) and three variants of foliar application of «KALNINI» (no treatment in phase V3, in phase R2). The survey included assessment of morphometric parameters, symbiotic activity (number, weight and colour of tubers), photosynthetic potential (SPAD index), yield and protein and fat content in grain. The findings showed that the separate use of «RIZOLINE-r» increased nodule number by 48.9 %, SPAD- value – by 16.6 %, yield – by 22.4 %, and protein content – by 1.2 % compared to the control. Foliar application of «KALNINI» contributed to the increase of these indicators by 28.9; 10.2; 13.3 and 0.9 % respectively. The maximum values were achieved with the combined use of both preparations: tuber growth +64.4 %, SPAD +25.8 %, yield +35.7 %, protein +1.9 %, fat +0.8 % compared to the untreated control. A close positive correlation was established between the photosynthetic SPAD index and yield (r = 0.86), bubble and protein mass (r = 0.74), SPAD and fat content (r = 0.97). This allows us to recommend the combined use of «RIZOLINE-r» and «KALNINI» as an effective element of soybean cultivation technology under organic farming conditions to stimulate symbiosis, activate photosynthesis and improve the quality indicators of the crop. Key words: organic farming, soybean, inoculation, biostimulant, symbiosis, photosynthesis, yield, biochemical composition.