Irrigation and fertilization effects on arbuscular mycorrhizal fungi depend on growing season in a dryland maize agroecosystem

Arbuscular mycorrhizal (AM) fungi form mutualistic associations with most terrestrial plants and can enhance crop water and nutrition acquisition. It is thus important to elucidate the interactive impacts of water and fertilizer management on AM fungi for sustainable agriculture. Our study investigated the effects of irrigation (wellwatered vs. drought) and fertilization (nitrogen (N), phosphorus (P), and NP) on AM fungi in soil and roots of maize (Zea mays L.) across three consecutive growth phases (jointing, tasseling, and mature). Drought significantly decreased AM fungal extra-radical hyphal density and root colonization rate at the tasseling and mature phases, respectively. Nitrogen and NP fertilization exerted a negative effect on AM fungal spore density under drought at the mature phase. Drought decreased AM fungal richness in soil and roots at the jointing and mature phases, respectively. AM fungal community composition in soil and roots was significantly different between the jointing phase and the tasseling and mature phases. AM fungal community composition was influenced by fertilization at the tasseling phase in soil, but by irrigation at the jointing and tasseling phases in roots. Our findings highlight the differential response of AM fungi in soil and roots to drought and fertilization during the various phases of maize development in this dryland agroecosystem.