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Effects of different improvement regimes on organic carbon pools of soils newly developed from parent material of Mollisols.

YUAN Ya-ru1, HAN Xiao-zeng2, LI Na2*, YOU Meng-yang2, ZOU Wen-xiu2   

  1. (1College of Geographical Science, Harbin Normal University, Harbin 150025, China; 2Key Laboratory of Mollisols Agroecology, Northeast Institute of Geography and Agroecology, Chinese Academy of Sciences, Harbin 150081, China).
  • Online:2020-04-10 Published:2020-04-10

Abstract: The fractionation technique of aggregate and occluded microaggregate was used to separate soil organic matter into three carbon (C) fractions: total coarse particulate organic matter (total cPOM) as labile C pool, total fine particulate organic matter (total fPOM) as slow C pool, and total silt and clay particles (total S&C) as passive C pool. We examined the effects of different management practices on soil organic C (SOC) pools after 8-year soil development from parent material of Mollisols, aiming to provide reference for the rapid restoration of soil fertility of seriously eroded black soil. There were six treatments: no-tilled vegetation restoration under natural fallow (NatF), no-tilled vegetation restoration under alfalfa plantation (Alfa), tillage under corn-soybean cropping system without chemical fertilizers application (F0C0), tillage under corn-soybean cropping system with chemical fertilizers application (F1C0), tillage under cornsoybean cropping system with chemical fertilizers plus fixed amount of maize straw and simulated organic manure (F1C1), tillage under corn-soybean cropping system with chemical fertilizers plus all biomass (all crop shoots, roots and seeds) returned (F1C2). The results showed that SOC pools (total C pool, labile C pool, slow C pool, and passive C pool) in all treatments were significantly improved after 8year soil development from parent material of Mollisols. F1C2 and F1C1 had the highest SOC content among all the treatments. Compared with NatF, SOC contents in F1C2, F1C1 and Alfa treatments were increased by 60.7%, 41.2% and 18.2%, respectively. There was no significant difference in SOC content between NatF and F0C0 or F1C0 treatments. The C contents in total cPOM, total fPOM and total S&C in F1C2 and F1C1 treatments were significantly higher than that in other treatments. F1C2 had higher C contents of the three C fractions than F1C1. Compared with NatF, the increment of C in Alfa treatment was mainly attributed to the enhancement of C in total S&C. There was no significant difference in C contents in total fPOM and total S&C between NatF and F1C0 or F0C0 treatments. The C content in total cPOM in F1C0 and F0C0 treatments was significantly lower compared with NatF. These results suggested that higher amount of C input combined with chemical fertilizer in agricultural ecosystem of black soil under corn-soybean rotation and traditional tillage systems could increase both labile and recalcitrant C pools, which could accelerate the improvement of parent material of Mollisols and thus be an effective measure to improve soil organic matter in seriously degraded black soil region.