Inoculation effects of two South African cyanobacteria strains on aggregate stability of a silt loam soil

Abstract

Two South African cyanobacteria strains (coded 3g and 7e) of the genus Nostoc were evaluated for improvement of the aggregate stability of a silty loam soil with low organic C content and compared with Nostoc strain 9v isolated from a Tanzanian soil. The soil was either cropped with maize or noncropped and inoculated with the three strains in a glasshouse. After 42 days, the aggregate stability based on mean weight diameter (MWD) and fragment size distribution were determined by fast wetting, wet stirring and slow wetting methods. Inoculation of the soil with strains 3g and 7e improved the soil's MWD and increased its proportion of large aggregates, particularly in the cropped soil. The opposite was the case for aggregates in soils inoculated with the reference strain 9v. Strain 3g resulted in greater improvement of MWD estimated by fast wetting, while strains 7e and 9v improved aggregate stability estimated by wet stirring. Improvement of aggregate stability was more related to exocellular polysaccharide (EPS) content than organic C. The results suggest that indigenous strains with high potential for EPS production could improve the soil structural stability of degraded soils in South Africa.

Cyanobacteria Inoculation Improves Soil Stability and Fertility on Different Textured Soils: Gaining Insights for Applicability in Soil Restoration

“…Previous experiments have also shown that inoculation of Nostoc sp., Scytonema sp., Microcoleus vaginatus, and Phormidium sp. increase soil aggregation on sand (McKenna Neuman et al, 1996;Hu et al, 2002;Chen et al, 2006;Xie et al, 2007), sandy loam (Malam Issa et al, 2007), silty and silt loam (Maqubela et al, 2009(Maqubela et al, , 2012 and clay soils (Falchini et al, 1996;de Caire et al, 1997;Nisha et al, 2007).…”

“…However, studies on their application for biofertilizing and bioconditioning degraded arid soils are relatively few. Experiments under laboratory (Maqubela et al, 2009(Maqubela et al, , 2012Mugnai et al, 2018) and outdoor conditions (Wang et al, 2009;Wu et al, 2013;Lan et al, 2017;Park et al, 2017;Zaady et al, 2017) point to positive results in terms of soil stability and fertility.…”

Effects of biocrust on soil erosion and organic carbon losses under natural rainfall

“…Studying the influence of different biotic components on soil stability, Chaudhary et al (2009) found that biocrusts had a stronger effect on soil surface stability than plants and arbuscular mycorrhizal. Inoculation of soils with algae and cyanobacteria has been found to increase the amount of water-stable aggregates due to entanglement of soil particles by cyanobacterial filaments and their sticky exopolysaccharides, and their role in enhancement of soil organic matter content and stimulation of soil microbial activity (Bailey et al, 1973;Rogers and Burns, 1994;De Caire et al, 1997;Malam Issa et al, 2001;Maqubela et al, 2009Maqubela et al, , 2012. Exopolysaccharides also make soil aggregates hydrophobic, and can improve soil aggregation by retarding the delay of entrapped air, and thereby, their breakdown (Nisha et al, 2007;Maqubela et al, 2012).…”

“…Inoculation of soils with algae and cyanobacteria has been found to increase the amount of water-stable aggregates due to entanglement of soil particles by cyanobacterial filaments and their sticky exopolysaccharides, and their role in enhancement of soil organic matter content and stimulation of soil microbial activity (Bailey et al, 1973;Rogers and Burns, 1994;De Caire et al, 1997;Malam Issa et al, 2001;Maqubela et al, 2009Maqubela et al, , 2012. Exopolysaccharides also make soil aggregates hydrophobic, and can improve soil aggregation by retarding the delay of entrapped air, and thereby, their breakdown (Nisha et al, 2007;Maqubela et al, 2012). Biocrusts also form small mounds on the soil surface that reduce the velocity of overland flow, thus diminishing its capacity to transport suspended sediments (Rodríguez-Caballero et al, 2012).…”