Optimizing the growth of forage and grain legumes on low pH soils through the application of superior Rhizobium leguminosarum biovar viciae strains

Abstract

Climate variability and current farming practices have led to declining soil fertility and pH, with a heavy reliance on fertilizers and herbicides. The addition of forage and grain legumes to farming systems not only improves soil health but also increases farm profitability through nitrogen (N) fertilizer cost offsets. However, the formation of effective symbioses between legumes and rhizobia can be unreliable and is considered at risk when combined with dry sowing practices such as those that have been designed to obviate effects of climate change. This research was initiated to improve the robustness of the legume/rhizobia symbiosis in low pH, infertile and dry soils. Production from two cultivars of field pea (Pisum sativum) and two species of vetch (Vicia spp.), and symbiotic outcomes when inoculated with a range of experimental rhizobial strains (Rhizobium leguminosarum biovar viciae), was assessed in broad acre field trials which simulated farmer practice. New rhizobia strains increased nodulation, N fixation, produced more biomass and higher seed yield than comparator commercial strains. Strain WSM4643 also demonstrated superior survival when desiccated compared to current commercial strains in the laboratory and on seed when delivered as inoculant in peat carriers. WSM4643 is a suitable prospect for a commercial inoculant in Australia and other agricultural areas of the world where growing peas and vetch on soils generally considered problematic for this legume/rhizobia symbiosis. A particular advantage of WSM4643 may be that it potentiates sowing inoculated legumes into dry soil, which is a contemporary response by farmers to climate variation.

Grass–Legume Mixture with Rhizobium Inoculation Enhanced the Restoration Effects of Organic Fertilizer

“…The grassland yield and soil nutrient contents, especially contents of soil total nitrogen and nitrate nitrogen, significantly increased after testing the effectiveness of a grass–legume mixture inoculated with Rhizobium based on the application of organic fertilizer compared with CK. The symbiotic nitrogen fixation between leguminous forage and Rhizobium could be responsible for such an increase in yield and soil nutrients in degraded artificial grassland [ 44 ], indicating that the grass–legume mixture inoculated with Rhizobium can strengthen the positive impacts of the application of organic fertilizer on the yield and soil nutrient contents of degraded artificial grassland.…”

Contribution of Biofertilizers to Pulse Crops: From Single-Strain Inoculants to New Technologies Based on Microbiomes Strategies

“…Climate variability and farming management practices with a heavy reliance on fertilizers and herbicides can result in a reduction in soil carbon, fertility, and pH, and not rarely, can contribute to an increase in the incidence of plant disease. In legume production areas where rhizobial contribution to BNF is at risk, a solution was sought based on the selection of Rlv strains by superior symbiotic performance and saprophytic competence [ 29 ]. A large rhizobial collection obtained from acid soils was the source for fourteen strains with a superior BNF capacity, higher than 78% nitrogen derived from the atmosphere, and twenty-two strains that showed a high soil survival capacity into the next season [ 30 ].…”

Grain Legume Yield Responses to Rhizobia Inoculants and Phosphorus Supplementation Under Ghana Soils: A Meta-Synthesis

“…In the context of small-scale farming in Africa, many soils are highly deficient in the available P, which results in a low yield of crops (Manyong et al, 2001 ; Jemo et al, 2015 ). Other various edaphic factors impair rhizobia development in the soil, in particular soil N availability (Nishida and Suzaki, 2018 ), soil pH (Yates et al, 2021 ), drought (Staudinger et al, 2016 ), salinity (Etesami and Adl, 2020 ), clay or organic matter content (Thilakarathna and Raizada, 2017 ), elevated temperature (Basu and Kumar, 2020 ), on-farm management practices, natural non-effective rhizobacteria in native soils (Iturralde et al, 2019 ), and “competitor microbes” or parasitic organisms (Costa et al, 2021 ).…”