University of Guilan Caspian Journal of Environmental Sciences 1735-3033 23 3 2025 07 01 Efficiency of phytomeliorants and bacillus biologicals in increasing alfalfa yield 643 654 8942 10.22124/cjes.2025.8942 EN Vitaly Khlyustov Professor of the Department of Land Management and Forestry, Russian State Agrarian University – Moscow Timiryazev Agricultural Academy, Timiryazevskaya Str., Moscow, 127434, Russian Federation Yuri Bezborodov Head of the Department of Land Management and Forestry, Russian State Agrarian University –Moscow Timiryazev Agricultural Academy, Timi-ryazevskaya Str., Moscow, 127434, Russian Federation Heba Ismail Student, Russian State Agrarian University – Moscow Timiryazev Agricultural Academy, Timiryazevskaya Str., Moscow, 127434, Russian Federation Journal Article 2025 08 06 The study was conducted to examine the effect of alfalfa-based compost and <em>Bacillus</em> biologicals on alfalfa (<em>Medicago sativa</em>) yield in the arid climate of the Syrian Arab Republic. The main research objective was to identify opportunities to increase crop productivity with fertilizers and biologicals. We conducted a field experiment over a three-year period (2020-2022), including four variants: control, compost, biologicals, and combined use of compost and biologicals. The data were subjected to a two factor analysis of variance. We also used pairwise and multiple regressions to analyze how the factors influence the yield. The results proved that compost and biologicals significantly increased alfalfa yield compared to the control. The greatest effect was observed with the combined use of compost and biologicals, which confirms the hypothesis of a synergistic effect. The analysis of variance showed the significance of the differences between the experimental tests and the cultivation years at the 5% and the 1% significance levels. Pairwise comparisons using the Tukey’s criterion also confirmed the presence of statistically significant differences between the experiment variants. The regression analysis with dummy variables allowed us to develop a model explaining the dependence of the yield on the cultivation year and the ameliorant type. The high value of the coefficient of determination (R² = 0.982) and the significance of the coefficients of the regression equation confirm the model reliability. The results can be used to develop recommendations for the use of organic and biological ameliorants in arid climates, which helps improve agrotechnical characteristics and increase the yield of agricultural crops. https://cjes.guilan.ac.ir/article_8942_4b6e6c99bf76342e16963113269cc696.pdf