3.1.2 Soil aggregate and glomalin-related soil protein
The weight percentage of soil aggregate varied with its size fractions (Fig.1). In all N addition treatments, MWD values ranged from 1.48-1.74 mm. The content of large aggregates (2-5 mm) and MWD value was significantly higher in the HN treatment compared to the CK.
N addition exerted significant effect on the EE-GRSP and T-GRSP content of soil aggregate. The contents of EE-GRSP ranged from 1.36-4.29, and T-GRSP ranged from 3.73-13.50 mg·g-1 (Fig.2). \soutThough two-way ANOVA analyze, there were interaction effect between N addition and aggregate fractions on GRSP (P<0.01). Among all treatments, the GRSP content of soil aggregate <0.25 mm was the highest; GRSP content varied according to the amount of N addition. N addition increased the content of EE-GRSP and T-GRSP in soil aggregates, and reached the maximum in the MN treatment. N addition increased the EE-GRSP content of soil aggregates by 60.6% to 118.7%, 12.0% to 77.2%, 5.0% to 60.5%, and 16.3% to 56.2% for each particle size (<0.25 mm, 0.25-1 mm, 1-2 mm, and 2-5 mm), respectively. N addition increased the T-GRSP content of soil aggregates by 45.5% to 87.6%, 25.5% to 88.4%, 44.5% to 105.2% and 51.1% to 86.4% for each particle size, respectively.