Early seedling and seasonal N2-fixing symbiotic activity of two soybean [Glycine max (L.) Merr.] cultivars inoculated with Bradyrhizobium strains of diverse origin

Abstract

In areas with a short growing season the poor adaptability of soybean [Glycine max Merr. (L.)] to cool soil conditions is considered the primary yield limiting factor. Soybean requires temperatures in the 25 to 30 °C range for optimum N2-fixation and yield. Field studies were conducted in 1990 and 1991 at Montreal, Quebec to determine whether adaptability to cool soil conditions, with respect to earlier symbiosis establishment and function, existed among either Bradyrhizobium strains or soybean genotypes. An early maturing isoline of the soybean cultivar Evans and the cultivar Maple Arrow were inoculated with one of four strains isolated from the cold soils of Hakkaido, northern Japan, or the commercially used strains 532C or USDAll0, at two planting dates. Plot biomass and nodulation were assessed at seedling(V2), and flowering(R2) growth stages and harvest maturity. Soybean genotypes did not differ for pre-flowering nodulation or Nz-fixation in the cool spring conditions of the first year. Seasonal N2-fixation rates were also determined at the final harvest by the N-balance and 15N-isotope dilution methods. Significantly higher symbiotic activity was found for two of the four Hakkaido strains and was reflected in higher final soybean seed yield and total Nz-fixation for the growing season, as compared to the two commercial strains. Planting 14 days earlier resulted in greater early vegetative and total seasonal N 2 fixation and yield in the second year when soil temperatures were warmer, emphasizing the need for the development of soybean-Bradyrhizobium combinations superior in nodule development and function under cool soil conditions.

Inoculation of soybean (Glycine max. (L.) Merr.) with genistein-preincubated Bradyrhizobium japonicum or genistein directly applied into soil increases soybean protein and dry matter yield under short season conditions

“…Three days elapsed between removal of the fumigation canopy and planting (Lynch and Smith, 1993b). The experiments were carried out on two adjacent sites, both on a Chicot light sandy loam soil.…”

“…The decreases in soybean yield at low temperatures are mainly due to nitrogen rather than to carbon limitation (Thomas and Sprent, 1984). However, the early infection processes are the most sensitive, with an event occurring during the first 12 h being particularly sensitive to temperature (Lynch and Smith, 1993b;Zhang and Smith, 1994). In most areas of Canada early vegetative growth of soybean occurs under suboptimal temperatures.…”

Physiological adaptation to low temperatures of strains of Rhizobium leguminosarum bv. viciae associated with Lathyrus spp.1

“…trifolii are reduced by lowering the temperature [7]. Consequently, growth of legumes can be significantly reduced as reported with alfalfa [8] and soybean [9] under cold conditions in Canada. In many studies, cold‐adapted rhizobia isolated from arctic or sub‐arctic regions showed the capacity to improve symbiotic nitrogen fixation and yield of legumes under low temperature conditions [10,11].…”

Enhanced Soybean Plant Growth Resulting from Coinoculation of Bacillus Strains with Bradyrhizobium japonicum

“…Soybean needs relatively warm temperatures for development; for example, the optimum temperature for soybean symbiotic nitrogen fixation is 25 to 30°C. However, in some short growing season regions, such as southwestern Quebec, the mean soil temperature at a depth of 10 cm is 10°C in mid‐May and 15°C in June (Lynch and Smith, 1993). Suboptimal root zone temperatures (RZTs), such as these, strongly inhibit soybean early growth and, especially, establishment of the soybean‐ B. japonicum nitrogen fixing symbiosis.…”