Arbuscular mycorrhizal development, glomalin-related soil protein (GRSP) content, and rhizospheric phosphatase activitiy in citrus orchards under different types of soil management

The arbuscular mycorrhizal (AM) status with respect to colonization of different AM structures in the citrus roots, spore density and hyphal length density, GRSP content, and phosphatase activity in the citrus rhizosphere were investigated in the orchards at Zigui county of the Three Gorges Region, S China. Four soil managements, no-tillage and natural grass (NN), no-tillage and sod culture (NS), half-tillage and film mulching (HT), and clean-tillage (CT) were employed in those citrus orchards. Our survey showed heavy AM colonization (36%-89%), indicating a high AM dependency of citrus in our experimental orchards. The colonization of different AM structures, spore density, hyphal length density, GRSP content, and phosphatase activity varied greatly between the no-tillage and tillage citrus orchards. The highest colonization of different AM structures except the ratio of root length with vesicles (RLV), spore density, hyphal length density, GRSP content, and phosphatase activity was observed in the no-tillage orchards, and the lowest was found in the tillage orchards. A cluster analysis based on the similarity in AM status, GRSP content, and phosphatase activity showed similarities between the NS citrus orchards and the NN citrus orchards. The data presented here demonstrate that tillage reduced the total AM colonization (RLT), spore density, hyphal length density, GRSP content, and phosphatase activity, while those were recovered in the no-tillage citrus orchards. So, we propose that no-tillage and planting grass is an effective way for citrus production and improvement of soil quality in orchards of the study area.