Assessing the influence of farm fertility amendments, field management, and sorghum genotypes on soil microbial communities and grain quality

Authors: COBB, ADAM - Oklahoma State University; WILSON, GAIL W. - Oklahoma State University; GOAD, CARLA - Oklahoma State University; Bean, Scott; TESSO, TESFAYE - Kansas State University; Wilson, Jeff

Submitted to: Applied Soil Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/10/2016
Publication Date: 10/1/2017
Citation: Cobb, A.B., Wilson, G.T., Goad, C.L., Bean, S.R., Tesso, T.T., Wilson, J.D. 2017. Assessing the influence of farm fertility amendments, field management, and sorghum genotypes on soil microbial communities and grain quality. Applied Soil Ecology. 119:367-374. https://doi.org/10.1016/j.apsoil.2017.06.010.
DOI: https://doi.org/10.1016/j.apsoil.2017.06.010

Interpretive Summary: The primary objectives of this study were to (1) assess the productivity and grain quality of hybrid and open-pollinated sorghum genotypes grown in low nutrient soil with added commercial fertilizers or worm compost, (2) to assess yield and grain quality differences between sole crop sorghum and sorghum intercropped with cowpea (3) to assess the relative abundance of microbial community functional groups, including AM fungi, associated with each genotype, treatment, and cropping system combination and (4) to assess the potential role of AM colonization of host-plant roots on grain production and nutritional quality. Four genotypes of grain sorghum (two commercial hybrids and two open-pollinated cultivars) were assessed for grain production, protein and mineral concentrations, grain physical properties, and starch quality characteristics. Genotype had a significant effect on grain nutritional quality, and grain physical characteristics, with the open-pollinated genotypes characterized by higher Ca, Mg, P, S, and protein concentrations, compared to hybrid genotypes, and hybrids characterized by a higher proportion of grain amylose and completely hydrolysable starch, regardless of fertilizer or management treatment. Intercropping and/or amendment with worm compost generally resulted in similar or improved grain quality as compared to sole cropping and/or amendment with commercial fertilizers. Differences were detected in the microbial communities associated with different genotypes, and there a higher fungal to bacterial biomass ratio present following amendment with worm compost. The restoration of these microbial communities on farms is an important strategy to enhance soil sustainability while reducing reliance on commercial fertilizers.

Technical Abstract: Four genotypes of grain sorghum (two commercial hybrids and two open-pollinated cultivars) were assessed for grain production, protein and mineral concentrations, grain physical properties, and starch quality characteristics. Genotypes were also characterized for their influence on soil microbial communities, particularly inter- and extra-radical arbuscular mycorrhizal (AM) fungi, in a field trial at two sites. All genotypes were grown as sole crops, while one commercial hybrid and one open-pollinated cultivar were also intercropped with cowpea to compare results between the two farm management systems. All genotypes were grown in low-fertility soils at Oklahoma State University Wes Watkins Research and Extension Center (Lane, Oklahoma, USA) and the Samuel R. Noble Foundation (Ardmore, Oklahoma). We established three treatments: a non-amended control, commercial fertilizers (N&P), and worm compost. Genotype had a significant effect on grain nutritional quality, and grain physical characteristics, with the open-pollinated genotypes characterized by higher Ca, Mg, P, S, and protein concentrations, compared to hybrid genotypes, and hybrids characterized by a higher proportion of grain amylose and completely hydrolysable starch, regardless of fertilizer or management treatment. Intercropping and/or amendment with worm compost generally resulted in similar or improved grain quality as compared to sole cropping and/or amendment with commercial fertilizers. Differences were detected in the microbial communities associated with different genotypes, and there a higher fungal to bacterial biomass ratio present following amendment with worm compost. Grain production was not significantly different between genotypes or treatments, but percentage AM root colonization was significantly greater for plants grown in soil amended with worm compost, as compared to commercial fertilizers.