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

Abstract

A discrete number of studies have been conducted on the effects of rhizobia (Rhz) inoculants, phosphorus (P) management, and combined application of Rhz and P fertilizer on the enhancement of grain legume yield across soils of Ghana and elsewhere. However, the extent to which the various inoculated Rhz strains, P application, and combined application of Rhz + P studies contribute to improving yield, performed on a comprehensive analysis approach, and profit farmers are yet to be understood. This study reviewed different experimental studies conducted on soybean (Glycine max (L.) Merr.), cowpea (Vigna unguiculata [L.] Walp), and groundnut (Arachis hypogaea [L.]) to which Rhz inoculants, P supplements, or Rhz + P combination were applied to improve the yield in Ghana. Multiple-step search combinations of published articles and multivariate analysis computing approaches were used to assess the effects of Rhz inoculation, P application, or both application of Rhz and P on yield variation. The random forest (RF) regression model was further employed to quantify the relative importance of various predictor variables on yield. The meta-analysis results showed that cowpea exhibited the highest (61.7%) and groundnut (19.8%) the lowest average yield change. The RF regression model revealed that the combined application of Rhz and P fertilizer (10.5%) and Rhz inoculation alone (7.8%) were the highest explanatory variables to predict yield variation in soybean. The Rhz + P combination, Rhz inoculation, and genotype wang-Kae explained 11.6, 10.02, and 8.04% of yield variability for cowpea, respectively. The yield in the inoculated plants increased by 1.48-, 1.26-, and 1.16-fold when compared to that in the non-inoculated cowpea plants following inoculation with BR 3299, KNUST 1002, and KNUST 1006 strains, respectively. KNUST 1006 strain exhibited the highest yield increase ratio (1.3-fold) in groundnut plants. Inoculants formulation with a viable concentration of 109 cells g−1 and a minimum inoculum rate of 1.0 × 106 cells seed−1 achieved the highest average yield change for soybean but not for cowpea and groundnut. The meta-analysis calls for prospective studies to investigate the minimum rate of bacterial cells required for optimum inoculation responses in cowpea and groundnut.

Exploring the potential of mapped soil properties, rhizobium inoculation, and phosphorus supplementation for predicting soybean yield in the savanna areas of Nigeria

“…Earlier work demonstrated increased soybean yields with the combination of Rh inoculants and P fertilizer in West African soils. The observed higher yields of 1,188 kg ha −1 in SS, 1,203 kg ha −1 in NGS, and 1,397 kg ha −1 in SGS for the Rh + P application in West Africa (Ronner et al, 2016;Ulzen et al, 2018;Buenor et al, 2022). The authors reported an average yield increment of 815 kg ha −1 from the combined application of Rh + P, along with an increment in farmers' net profit.…”

“…However, higher biological N fixation and yield response are reported when the legume plants are fertilized with a moderate phosphorus (P) rate, particularly in many soils and climatic conditions in Africa where available P in the soil is low ( Jemo et al., 2010 ). The use of an appropriate strain of Rh inoculant and P fertilization practices to improve BNF legume production has been the subject of numerous studies in Sub-Saharan Africa ( Ronner et al., 2016 ; Ulzen et al., 2018 ; van Heerwaarden et al., 2018 ; Buenor et al., 2022 ). Those studies have reported yield increases ranging from 452 to 815 kg ha −1 and a net economic benefit of about 400 USD ha −1 through the combined application of Rh inoculants and P fertilizer.…”

Fertilizers for food and nutrition security in sub-Saharan Africa: An overview of soil health implications

“…Nutrient deficiencies in human diets, including those of Zn and Fe, are being exacerbated by climate change events such as water deficiency (116). Data from a previous study (34) is adapted in Table 2 to buttress the contribution of agronomic Zn fortification to human Zn nutrition under drought stress production conditions.…”

“…Grain Zn fortification via soil fertilization thus represents a significant nutritional outcome for critical populations that depend on grain stapes such as sorghum in the face of persistent climatic events such as drought such as in parts of SSA. A similar estimate can also be generated for Fe; aridity has been described as affecting the availability of Fe to humans (116).…”

Symbiotic effectiveness of Bradyrhizobium strains on soybean growth and productivity in Northern Mozambique

“…In a Large-scale study in 10 SSA countries including Mozambique, Malawi and Zimbabwe, van Heerwaarden et al (2017) reported more than 200 kg ha −1 yield increases in soybean due to rhizobial inoculation. A metaanalysis study of various soybean experiments conducted in Ghana showed 60% yield increase in the inoculated plants compared with the non-inoculated plants (Buernor et al, 2022). Masso et al (2016) and Ronner et al (2016) reported significant yield response of 447 kg ha −1 and 426 kg ha −1 , respectively to rhizobial inoculation in soybean.…”