Effects of Different Crop Rotation Systems on Soil Readily Oxidized Organic Carbon and Carbon Pool Activity Differences

Soil organic carbon pool activity and stability are important indicators that directly reflect soil quality. This study aimed to explore the effects of long-term crop rotation system on soil organic carbon, active organic carbon and soil carbon pool management index, so as to provide the scientific management of soil carbon pool and rational crop layout in black soil areas.

The experiment started in 2016, and 7 treatments were set up: potato continuous cropping (P-P), maize continuous cropping (M-M), soybean continuous cropping (S-S), soybean-maize rotation (S-M), soybean-potato rotation (S-P), maize-maize-potato rotation (M-M-P), and soybean-maize-potato rotation (S-M-P). P-P was used as a control. The characteristics of soil organic carbon (SOC), readily oxidizable carbon (ROC), inert organic carbon (IOC) and soil carbon pool management index (CPMI) in 0-60 cm soil layer at the harvest stage in 2022 and 2023 were analyzed systematically.

Compared with the P-P treatment, in 2022 and 2023: (1) SOC content under S-M-P and S-M treatment in 0-10 cm soil layer increased significantly by 10.22%-12.49% and 20.67%-36.75%, respectively. The M-M-P treatment of 10-20 cm soil layer significantly increased by 16.65% and 33.76%, respectively. SOC content under S-M-P and M-M-P treatments in 20-40 cm soil layer was significantly increased by 28.74%-36.78% and 48.78%-53.67%, respectively. In 2023, the S-M-P in 40-60 cm soil layer was significantly increased by 14.90% (P<0.05). (2) ROC₃₃₃ content in 0-10 cm soil layer under S-M and M-M-P treatment was significantly increased by 20.09%-20.41% and 34.94%-39.69%, respectively. ROC₃₃₃ of all rotation treatments in 10-20 cm soil layer increased significantly by 13.16%-26.32% and 28.98%-52.63%, respectively (P<0.05). (3) ROC₁₆₇ content in S-P, S-M and S-M-P treatments in 0-10 cm soil layer was significantly increased by 21.11%-35.46% and 42.33%-44.85%, respectively (P<0.05). (4) ROC_33.3 content in 0-10 cm soil layer under S-M-P treatment was significantly increased by 18.04% and 19.02%, respectively (P <0.05). (5) IOC of S-M-P treatment in 0-10 cm soil layer was significantly increased by 13.30% and 14.84%; M-M-P, S-M-P and S-M treatments in 20-40 cm soil layer significantly increased by 20.38%-52.51% and 59.56%-69.54%, respectively (P<0.05). (6) CPMI in 0-10 cm soil layer was significantly increased by 24.07%-28.13% and 41.46%-42.57% under S-M and M-M-P treatments, respectively. All rotation treatments in 10-20 cm soil layer were significantly increased by 17.34%-31.49% and 36.97%-61.11%, respectively (P<0.05).

In conclusion, maize-soybean, soy-maize-potato and maize-maize-potato rotation treatments were beneficial to improve soil carbon pool activity and increase soil carbon stability. Leguminous crop rotation could not only increase the activity of organic carbon pool but also maintain its stability, which was conducive to the stability of soil carbon pool balance in black soil.