Agrobiological bases of vetch (Vicia sativa L.) cultivation for seeds in the Central Russia using heterogeneous agrocenoses

Common vetch ( Vicia sativa L.) is widely cultivated in the Russian regions with different climate and edaphic conditions, whereupon a significant plant polymorphism and specific adaptation to environment and cultivation technologies are observed. Recently, a new breeding approach is being developed to created vetch varieties for grain forage use. Since 2002, a new such variety, the Lugovskaya 98, is recorded in the State Register of Selection Achievements of the Russian Federation. This variety differs significantly from those cultivated for green fodder. Particularly, there is no hydrocyanic acid which is the main anti-nutrienent, and the level of trypsin inhibitors is reduced allowing the seeds of Lugovskaya 98 vetch to be used as protein source in animal feeds with no extra processing. In vetch pure stands a significant lodging occurs due to peculiar architectonics and biological peculiarities of plant growth under temperate climate. This necessitates vetch cultivation in the mixes with support crops. A complementary support crop and its stand density must be selected specifically in accordance with local soil and climatic conditions. We compared vetch Lugovskaya 98 seed yield formation in binary agrocenoses with different crops under stand density gradients and found those mostly complementary to vetch with regard to seed yield and quality. Plant allelopathic interactions was shown to begin during early ontogenesis. At high sowing rate of oats ( Avena sativa L.) the vetch plant death increased up to 7-9 % compared to 3-4 % in the vetch pure stands. Vetch young growth was also 6 to 7 % suppressed in the mixes with white mustard ( Sinapis alba L.). In contrary, Phacelia tanacetifolia had no effect on vetch young growth and juvenile plants. Generally, the vetch generative development was the best in the mixes with oat and mustard plants when the sowing rates of the support crops were low (i.e., not more than 1.00-2.00 and 1.50-2.25 million seeds per hectare, respectively). In these cenoses the bean number averaged 8.8-9.1 per plant, or 714-758 per square meter. As sowing rates of a support crop increased, the bean number reduced by 7-12 %. The highest vetch seed biological yield (283.6 g per square meter) was discovered in the mixes with the white mustard at sowing rate of 1.50 million seeds per hectare, and rather high yield of 260.5-267.5 g per square meter was recorded with phacelia and oat plants when their sowing rates were the lowest. Completeness of harvesting and seed quality in vetch are known to depend significantly on lodging. Before harvesting, in vetch pure stands the lodging was 74 %, and in mixes with oat, mustard and phacelia plants it was 22-42 % (depending on the cereal sowing rates), 37-45 %, and 54-56 %, respectively. Actual vetch seed yield was the highest (1.51-1.57 ton per hectare) when the white mustard or oat plants were used in mixes at sowing rates of 1.50 and 3.00 million seed per hectare, respectively. Under excess rainfall during vegetation vetch/oat ensured a complete harvesting vetch seeds due to less lodging, and at low rainfalls the vetch/mustard mixes were more convenient. According to vetch seed germination of 93-96 % and vigor of 77-83 %, the vetch/oat and vetch/mustard mixes ensured the highest seed quality. In lodged pure vetch these parameters were reliably lower (85 % and 65 %, respectively).