Zero Tillage Systems Conserve Arbuscular Mycorrhizal Fungi, Enhancing Soil Glomalin and Water Stable Aggregates with Implications for Soil Stability

Abstract

Arbuscular Mycorrhizal (AM) fungi form mutualistic symbiotic relationships with approximately 80% of terrestrial plant species, while producing the glycoprotein glomalin as a structural support molecule along their mycelial network. Glomalin confers two benefits for soils: (1) acting as a carbon and nitrogen storage molecule; (2) the binding of soil microaggregates (<250 µm) to form larger, more stable structures. The present study aimed to test the hypothesis that a correlation between glomalin and soil aggregation exists and that this is influenced by the method of seedbed preparation. The soils from two crops of winter wheat in Hertfordshire, UK, practising either conventional (20 cm soil inversion) or zero tillage exclusively, were sampled in a 50 m grid arrangement over a 12 month period. Glomalin and water stable aggregates (WSA) were quantified for each soil sample and found to be significantly greater in zero tillage soils compared to those of conventional tillage. A stronger correlation between WSA and glomalin was observed in zero tillage (Pearson’s coeffect 0.85) throughout the cropping year compared to conventional tillage (Pearson’s coeffect 0.07). The present study was able to conclude that zero tillage systems are beneficial for AM fungi, the enhancement of soil glomalin and soil erosion mitigation.

The Tripartite Rhizobacteria-AM Fungal-Host Plant Relationship in Winter Wheat: Impact of Multi-Species Inoculation, Tillage Regime and Naturally Occurring Rhizobacteria Species

“…Microbial associations between plant and soil are highly complex and provide a myriad of interactions with a wide range of plant and soil benefits including increased soil fertility and aggregation [ 1 , 2 ], improved plant immunity and defence [ 3 ], increased plant biomass and carbon sequestration [ 4 ]. Arbuscular mycorrhizal (AM) fungi are one of the constituent organisms within the rhizosphere of an estimated 80% of terrestrial plants [ 1 ] forming mutualistic biotrophic symbiosis with host plants [ 5 ].…”

“…Within an agricultural setting, this can be of commercial importance for the amplified nutrient availability produced from AM fungal acquired soil bound nutrients, such as phosphorus, improving crop health, biomass and yield [ 7 ]. AM fungi can additionally provide benefits to the improvement of soil properties, such as carbon and aggregation [ 2 , 8 ]. However, in combination with Plant Growth Promoting Rhizobacteria (PGPR), soil fertility can be improved further [ 9 ].…”

“…Soil cultivation by conventional tillage (CT) has been shown to directly influence the abundance and diversity of the soil microbiome [ 20 ]. The hyphal networks of AM fungi are damaged by CT [ 21 ] resulting in decreased root cortical arbuscules [ 2 , 22 ]. The impact of tillage on rhizobacteria is relatively unknown.…”

“…The impact of tillage on rhizobacteria is relatively unknown. A tillage system reported to be detrimental to AM fungi development, i.e., CT [ 2 , 20 , 21 , 22 , 23 ], may benefit from inoculation with AM fungi. This benefit however may not be realised until later crop growth development stages.…”

“…The glycoprotein glomalin is produced by AM fungi along their mycelial network where it acts as a structural support molecule [ 24 ], functioning as an adhesive glue-like compound [ 25 ]. Its presence is indicative of AM fungal growth [ 2 ]. Naturally occurring PGPR and AM fungi in the field extracted soils have been determined by qPCR analysis.…”