Integrating irrigation management for improved grain yield of winter wheat and rhizosphere AM fungal diversity in a semi-arid cropping system

Irrigation of farmland is a popular agricultural practice in semi-arid areas in China. However, little is known about the impacts of different irrigation strategies on grain yield and soil microbial communities, particularly economically-important arbuscular mycorrhizal (AM) fungi. The aim of this study was to optimize irrigation strategies to integrate maximized grain yield, AM fungal diversity and water productivity (defined here as grain yield per unit water supplied). Six irrigation strategies consisting of different amounts of water supplied and time of supply were imposed for field-grown winter wheat (Triticum aestivum) in a typical cropping system in northern China. Results showed that all irrigation strategies significantly increased grain yield compared with the non-irrigation practice (P <0.01). Irrigation strategy (treatment WJF180) with a total of 180-mm water supplied at Wintering, Jointing, and Grain filling stages (60 mm each) achieved maximal grain yield and water productivity than other treatments. Irrigation strategies also significantly influenced mycorrhizal colonization on roots, fungal species and spore abundance in rhizosphere soil. A total of 17 AM fungal species belonging to Glomus, Acaulopora, Scutellospora and Entrophospora were detected in the soil. The relative abundance of Glomus was the highest and Entrophospora the lowest among the four fungal genera. WJF180-treated plots had the largest species richness and spore abundance in various sampling times with plant growth. Fungal diversity differed greatly among different plant phenological stages. There were significant interactions between irrigation treatments and plant growth stages on both grain yield and AM fungi (species diversity and spore abundance). Irrigation strategies in terms of water amount and watering time integrated with biological, environmental and crop management could have potential for improved grain yield and mycorrhizal diversity leading to maximized farmers' economic productivity and water-use efficiency.