Abstract: Plant growth is restricted in the reclaimed waste dumps due to the harsh habitat. In this study, a field experiment was conducted to explore whether the addition of a mixed microbial agent would have synergistic effects with organic fertilizer on reclaiming plants, Sophora flavescens. The mixed microbial agent was composed of three strains at dosages of 3.6, 10.8 and 18 g·m^-2 (T1, T2 and T3) applied in combination with organic fertilizer, while no microbial agent addition as control (CK). The growth characteristics of Sophora flavescens and the contents of C, N and P in stems, leaves and roots were examined to reveal the synergistic effects and mechanisms of combined application of microbial agent and organic fertilizer. The results showed that: (1) The combined application could promote plant growth. T2 treatment significantly increased plant root diameter, root fresh weight, root dry weight and bud number (P<0.05) by 26.49%, 122.76%, 109.84% and 21.41% respectively. The comprehensive growth characteristics of plants were in the order of T2>T1>T3>CK, suggesting that moderate dosage was more conducive to plant growth. (2) The combined application had different effects on plant nutrient contents, and significantly improved the total nitrogen content of stems and leaves, with T3 treatment having the most significant effect (an increase of 29.22%). However, it did not affect organic carbon content in stems, leaves and roots and total nitrogen and total phosphorus contents in roots, and was unfavorable to the improvement of total phosphorus content in stems and leaves (P<0.05). Plants were always limited by P during their growth. (3) The contents of organic carbon, total nitrogen and total phosphorus were higher in stems and leaves than those in roots. (4) The application of bacterial agent combined with organic fertilizer could increase C/P and N/P in stems and leaves (P<0.05), but did not affect C/N in stems and leaves, the C/P, N/P and C/N in roots. Our results indicated that medium dosage of microbial agent combined with organic fertilizer (T2) is more conducive to the growth of S. flavescens in the study area, but phosphorus fertilizer should be supplemented in time.

Key words: dump, microbial agent, land reclamation, redundancy analysis (RDA), opencut coal mine.