Rhizobium Inoculation of Cowpea in Brazilian Cerrado Increases Yields and Nitrogen Fixation

Abstract

Core Ideas Cowpea cropping after soybean is increasing in the Cerrado region of Brazil and can benefit from BNF.Soybean bradyrhizobia can abundantly nodulate cowpea but are often inefficient.Inoculated elite cowpea Bradyrhizobium strains increased grain yields.Nitrogen fixation inputs were increased by inoculation with selected cowpea bradyrhizobia.Nitrogen‐15 natural abundance showed inoculation increased N2 fixation by over 25 kg N ha–1 crop–1. Cowpea (Vigna unguiculata Walp.) is increasingly planted as a second season crop after soybean [Glycine max (L.) Merr.] in the Brazilian Cerrado region. Experiments were conducted at Sinop and Primavera do Leste in Mato Grosso State to investigate the impact of cowpea inoculation with recommended rhizobium strains on biological nitrogen fixation (BNF) and grain yield. Plants were either non‐inoculated, with or without 70 kg N fertilizer ha−, or inoculated with five rhizobium strains, separately or as a mixture. Nodulation and shoot dry matter (DM) were evaluated at 35 d after emergence (DAE). Dry matter and N accumulation were evaluated and BNF contributions quantified using 15N natural abundance at 50 DAE. Nodule number and dry weight were high regardless of inoculation treatment. However, several of the inoculation treatments at Sinop and Primavera do Leste promoted significant increases in total N at 50 DAE. At both sites, the 15N abundance results indicated that inoculation significantly increased BNF contributions from 36 to 64 kg ha− at Sinop and from 48 to 75 kg N ha− at Primavera. Grain yield was significantly increased from approximately 1200 to 1500 kg ha− by strains BR 3262 and INPA 03‐11B at the Primavera do Leste, and from approximately 850 to 1400 kg ha− by strain BR 3262 at Sinop. The results indicate inoculation of cowpea with elite rhizobium strains can increase BNF contributions and grain yields in the Brazilian Cerrado region, even when there are abundant populations of soybean rhizobium present in the soil.

Influence of Tillage Systems, and Forms and Rates of Nitrogen Fertilizers on CO2 and N2O Fluxes from Winter Wheat Cultivation in Oklahoma

“…The biomass contained about 32-80 kg N ha −1 at termination. The proportion of biologically fixed N by cowpea was not determined in this study but a previous study indicated that cowpea terminated 50 days after planting derived 55%-60% of total N in biomass from the atmosphere [29]. Thus, although cowpea might have increased the pool of N in soils through biological fixation, the biomass N was not transferred effectively to the following crop of winter wheat.…”

Seeds enriched with molybdenum improve cowpea yield in sub‐humid tropical regions of Brazil

“…Using different Bradyrhizobium strains, inoculation increased cowpea yield up to 12-fold in the State of Maranhão (Gualter et al, 2011). In addition, benefits of inoculation in cowpea were also reported in studies conducted close to the equator in Brazil (Farias et al, 2016;Silva, Favero, Xavier, Boddey, & Zilli, 2018) and Africa (Kyei-Boahen et al, 2017). Therefore, the results of these inoculation studies, the results of the current study, and the results of studies in which Mo supply + Rhizobium inoculation were used together on common bean (Almeida et al, 2013;Pacheco et al, 2012) indicate that both Mo-enriched seeds and inoculation should be encouraged to increase cowpea yield in sub-humid tropical regions.…”

The Biology of Legumes and Their Agronomic, Economic, and Social Impact

“…Biological N fixation by legumes (e.g., faba bean, lentil, pea, chickpea, alfalfa, red clover etc.) ranges from 21 to 389 kg ha −1 (Table 1) (Cazzato et al 2012;Nimmo et al 2013;Büchi et al 2015;Hossain et al 2016;Snapp et al 2017;Akter et al 2018;da Silva Júnior et al 2018;Dhamala et al 2018;Ntatsi et al 2018;Pampana et al 2018;Ntatsi et al 2019).…”