Effects of bio-organic fertilizer on soil microbial community and enzymes activities in walnut orchards of the Qinling-Bashan Region

A field experiment was conducted in Qinling-Bashan Region of Shaanxi province to investigate the influence of different fertilization treatments on soil microbial community, enzymes activities and soil nutrients in walnut orchards. There were three treatments, control (CK), conventional fertilizer treatment (T1) and bio-organic fertilizer treatment (T2). The effect of bio-organic fertilizer addition on microbial community metabolic profiles was analyzed with the Biolog (ECO Microplate) method. The results show that the average well color development (AWCD), Shannon index and richness index (S) of microbial community of the T2 treatment are all significantly higher than those of the T1 treatment. Utilization of six carbon source types by soil microbial community shows that the soil microbial community of the bio-organic fertilizer treatment enhances consumption of all the six carbon source types, which indicates the soil microbial community function is changed to some extent. Principal components analysis demonstrates that there are larger differences on utilization of carbon substrates by soil microbial community between the T2 and CK treatment and between the T1 and control, which indicates that the function of soil microbial community is modified by fertilization regimes. The soil sucrase, acidic phosphatase and dehydrogenase activities are improved significantly, and soil urease activity is changed significantly after the application of bio-organic fertilizer in comparison with the control, while soil catalase activities are similar between the two treatments. The contents of total soil nitrogen, total phosphorus, total potassium and available phosphorus of the T2 treatment are significantly higher than those of the CK. In addition, soil pH is increased in the T2 treatment, and decreased in the T1 treatment in comparison with CK treatment. It is concluded that application of bio-organic fertilizer could not only change the function of microbial community, improve the activities of soil sucrase, acidic phosphatase, urease and dehydrogenase, but also increase the contents of soil nutrients.