Arbuscular mycorrhizal fungal species composition, propagule density, and soil alkaline phosphatase activity in response to continuous and alternate no-tillage in Northern China

• Thirty species of arbuscular mycorrhizal fungi within seven genera were recovered.
• The lowest similarity in species composition recorded between NT and CT (J = 0.767)
• No significant changes in AM fungal spore density, species richness and diversity
• External mycelium length and soil alkaline phosphatase activity were NT > AT > CT.
• NT and AT maintained AM fungal occurrence and increased soil P-supply efficiency.

PurposeArbuscular mycorrhizal (AM) fungi provide a direct link between soil and roots, and are renowned for their ability to increase nutrient phytoavailability, notably phosphorus (P). The objective of this study was to evaluate influences of continuous and alternate no-tillage on soil AM fungal species composition and soil P-supply parameters.Materials and methodsIn June 2006, a long-term field experiment was established in a sandy loam soil under the rotation of summer maize (Zea mays L.) and winter wheat (Triticum aestivum L.) in Northern China, including conventional tillage (CT), no-tillage (NT) and alternate tillage (AT — tillage in the wheat season and no-tillage in the maize season). Top soil samples (0–15 cm) from four individual plots per treatment were collected before maize harvest on 18 September 2010. Soil AM fungal spores were isolated and identified, and the external mycelium length, soil alkaline phosphatase (ALP) activity and soil P content were also determined.Results and discussionThirty species of AM fungi within seven genera, Acaulospora, Claroideoglomus, Funneliformis, Glomus, Racocetra, Rhizophagus, and Scutellospora, were recovered. Some species sporulated differentially across the three treatments, and the lowest Jaccard index (J) of similarity in species composition was recorded between NT and CT (J = 0.767), but there were no significant differences in soil total P and available P contents, as well as in AM fungal spore density (SD), species richness (SR) and diversity indices, including Shannon–Wiener index (H′), Evenness (E) and Simpson's index (D). Compared with CT, NT rather than AT significantly increased (P < 0.05) the external mycelium length, soil ALP activity, and soil organic C content.ConclusionsOur results demonstrated the vital role of NT in maintaining external hyphae growth and soil ALP activity rather than in promoting AM fungal species diversity and spore density, and suggested that 4-year continuous NT will not cause degradation in either AM fungal community or soil P-supply efficiency.