Agronomic characteristics of soybean cultivars with late-season nitrogen application in supplementation to the inoculation of Bradyrhizobium spp.

Abstract

Late season nitrogen (N) applications may serve as cultural practices to increase soybean yield and grain protein concentration in modern high-yielding cultivars. A study to evaluate the response of soybean cultivars to late N application in supplementation to Bradyrhizobium spp. inoculation was conducted in two Brazilian Cerrado agricultural soils with medium and high fertility during the 2019/2020 growing season. Treatments were arranged in a randomized block design in a 2×2×5 factorial scheme: two agricultural production environments [UFMS 1 (medium fertility) and UFMS 2 (high fertility)], two soybean cultivars (TMG 7067 IPRO and BMX Bônus IPRO), and five late N application rates (0, 50, 100, 150 and 200 kg N ha-1), with four replicates. Canonical correlation analysis (CCA) was used to investigate the interrelationships between the groups of independent (agricultural production environments, soybean cultivars, and N application rates) and dependent (soybean agronomic traits) variables. Nitrogen rates were applied in topdressing at the R5.3 soybean growth stage. Late N applications did not affect soybean agronomic traits (plant height, first pod height, pod number per plant, grain number per pod, and 1,000-grain mass) and did not increase the grain protein concentration or yield of the soybean cultivars, regardless of the fertility level of the agricultural area. We conclude that when efficient strains of Bradyrhizobium spp. are used in soybean cropping in medium- and high-fertility Cerrado soils, there is no need to apply late rates of N fertilizer.

Understanding the contribution of soybean crop residues inoculated with Bradyrhizobium spp. and not harvested on nitrogen supply in off-season corn cultivars

“…The N concentrations in soybean straw and grains ranged from 24.7 to 25.1 g kg –1 and 55.7 to 57.2 g kg –1 , respectively ( Table 2 ). Nitrogen concentrations ranging from 25 to 30 g kg –1 is usually reported for soybean crop residues [ 27 ], while the N concentration observed in soybean grains commonly ranges from 55 to 70 g kg –1 [ 13 ]. Considering that 37% of the dry matter of soybean crop residues consists of carbon [ 27 ], the C:N ratio of soybean residues remaining on the soil surface is 15:1.…”

“…Approximately 80 kg of N is needed for each ton of soybean grain produced [ 11 ], which is fulfilled by biological N fixation (BNF) through symbiosis with strains of Bradyrhizobium spp. and by N uptake from the soil or applied with N fertilizers [ 12 , 13 ]. Therefore, residues from soybean plants (straw and grains) have a high N content when compared to the straw of grass plants, and these residues breakdown more easily, releasing N into the soil.…”

Produtividade da área e da água em soja irrigada para diferentes variedades e metodologias de manejo da irrigação

“…O plantio foi realizado no dia 24 de outubro de 2020, sendo elas: TMG 7067 (V1), 58i60RFSF IPRO (V2) e NA 5909 (V3), com sementes previamente tratadas com fungicida e micronutrientes, na densidade de 10, 13 e 15 plantas por metro linear, respectivamente, seguindo as orientações das empresas de sementes. V1 apresenta hábito de crescimento semideterminado e pertence ao grupo de maturidade 7.2 (Zuffo et al, 2022), já V2 possui crescimento indeterminado, pertencendo ao grupo de maturidade 5.8 (Chechi et al, 2020).…”