The Effect of <i>Rhizobium</i> Inoculation on the Nutritional Value of Crops in the Legume–Cereal Intercropping System in Northern Kazakhstan

In this study, the changes in yield, nutrient content, and amino acid levels in legume–cereal grass mixtures were qualitatively evaluated depending on the legume–cereal combination and inoculation with preparations based on <i>Rhizobium</i>. This study, taking into account the biological characteristics of legume forage crops, used inoculations with strains of nodule bacteria and associative nitrogen fixers to enhance the process of the nitrogen fixation of mixed crops of legumes and cereal. The aim of this study was to compare the yields and nutritional values of monocultures and mixed crops, as well as to determine the effects of preparations based on strains of nodule bacteria and the associated nitrogen fixer on the photosynthetic activity and yield of combined annual legume–grain crops. A comparative study of forage crop biomass was conducted to analyze crude protein, fiber, carotene, and amino acid content in monocultures and legume–cereal mixtures, with and without the use of nodule-bacteria-based preparations (Rhizotorphin, Mizorine, Flavobactrin, and Azolene). The combined effect of crop mixtures and biological products led to increased green mass yield, protein content, and feed productivity. Notably, two-component mixtures with Rhizotorphin inoculation increased green mass yield by 8.79%, while three-component mixtures saw a 16.49% increase. The oat–pea mixture showed the most significant amino acid improvements, with lysine increasing by 6.26% and tyrosine by 3.24%. The general conclusion reached by the two-year experiment of 2022–2023 in the hill–plain zone of northern Kazakhstan is that double grass mixtures treated with nodule bacteria are more productive than monoculture crops in this area. These results suggest that inoculation with bacterial strains can effectively enhance the productivity of forage crops in northern Kazakhstan, providing a basis for future recommendations on optimizing herbaceous crop combinations. It is recommended to grow annual forage crops in mixtures with legumes to produce highly nutritious feeds with high metabolic energy in terms of biochemical composition.