Exogenous easily extractable glomalin-related soil protein promotes soil aggregation, relevant soil enzyme activities and plant growth in trifoliate orange

© 2015, Institute of Agricultural and Food Information. All rights reserved. Studies on glomalin-related soil protein (GRSP) have focused on soil aggregation and fungal physiology, whereas it is not known how exogenous GRSP could positively impact on these processes, soil enzyme activity and plant growth. Easily extractable GRSP [EE-GRSP, 0.022 mg protein/mL citrate buffer (20 mmol, pH 7.0)] from a 26-year-old citrus orchard was exogenously applied into 5-month-old potted trifoliate orange (Poncirus trifoliata) for 3 months to evaluate effects on soil water-stable aggregate distribution, relevant soil enzyme activities and plant growth. Depending on the applied concentrations as 1/2, 1/4 or full strength, exogenous EE-GRSP generally significantly increased the distribution of soil water-stable aggregates and mean weight diameter (MWD, an aggregate stability indicator). Values of MWD and plant biomass production curvilinearly positively correlated with exogenous EE-GRSP applications. Exogenous EE-GRSP generally significantly increased the activity of rhizospheric polyphenol oxidase, peroxidase, acid and alkaline phosphatase. Both the 1/2-strength and 1/4-strength, but not the full-strength exogenous EE-GRSP, significantly stimulated plant growth performance. Our results firstly demonstrated the positive contribution of exogenous EE-GRSP to soil aggregation, relevant rhizospheric enzyme activities and/or plant growth, which has important implications for exploring GRSP in enhancing soil structure and/or plant performance.