Objectives The effects of different agricultural management measures (tillage intensity, fertilization, and crop rotation) on soil chemical properties, enzyme activities, and yield were studied to provide a basis for selecting suitable soil quality evaluation indicators that were sensitive to external disturbances.
Methods In May 2019, 0–15 cm soil samples were collected from three long-term agricultural experimental stations in OHHO (initiated in 1963), OHWO (initiated in 1962), and ORAD (initiated in 1992). The experimental design was no-tillage (NT), conventional tillage(CT), and minimum tillage (MT) combined with crop rotation (corn, oats, herbage) and monoculture cropping (corn) set up at OHHO and OHWO experimental stations. At the ORAD experimental station, the design was NT, CT combined with fertilization and no fertilization (with or without mulch), respectively. The pH, total nitrogen (TN), total carbon (TC), soil texture (clay, silt, and sand), β-glucosidase, arylsulfatase, and fluorescein diacetate activity of soil samples were measured in the same year.
Results There was no significant difference in pH among the treatments at OHWO. The pH of OHHO rotation COH (or single-cropping CCC) combined with MT was (P < 0.05) higher than other treatments. The pH of rotation, mulch, fertilization (or no fertilization) combined with NT (PWY2-NT, PWY-NT), and WFa-NT, WFa-CT was (P < 0.05) significantly higher than other treatments at ORAD. Tillage and crop rotation affected soil pH, but there was no consistent change in the trend, and nitrogen fertilizer reduced soil pH except PWY2-NT treatment. Total nitrogen and carbon contents of COH-NT, PWY2-NT, and Wfa2-NT were significantly higher than other treatments, suggesting that rotation and no-tillage combined with fertilization significantly increased soil TN and TC content. The yield was not significantly different (P > 0.05) among treatments at OHHO and OHWO sites. Besides the effect of agricultural management on yield, we found that the yield was also influenced by plant diseases, pests or unexpected seasonal occurrence of natural disasters. The highest β-glucosidase, arylsulfatase, and fluorescein diacetate hydrolysis activities were observed under crop rotation with no-till at the three experimental sites. β-glucosidase exhibited variation among COH-MT, COH-CT, CCC-NT, CCC-MT, and CCC-CT. It also differed between PWY2-NT and PWY-NT, WFa2-CT and WFa-CT. However, TC was not different (P > 0.05) among the treatments. The correlation between β-glucosidase and TN, TC, arylsulfatase was 5% or 1%.
Conclusions The evaluation indicators sensitivity to external disturbance is in the order of β-glucosidase activity > total carbon > yield. According to the β-glucosidase activity, no-tillage combined with crop rotation is a satisfactory agricultural management measure to improve soil quality.
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