Effects of Long-term Organic Fertilization on the Content of Soil Organic Phosphorus Fractions and Abundance of Soil Microorganism

The effects of different fertilization regimes on soil organic phosphorus fractions (Po), the abundances of bacteria, fungi, and microorganisms associated with soil organic phosphorus transformation (phoD-harboring microbial), and alkaline phosphatase (ALP) were explored by analyzing soil samples collected from a long-term fertilization experimental site. A single-factor randomized block design was adopted and five treatments were set up as follows: (1) CK, no fertilizer treatment; (2) NK, N and K fertilizer treatment; (3) NPK, N, P and K fertilizer treatment; (4) M, organic fertilizer treatment; (5) NPKM, organic and inorganic fertilizers treatment. Results show that compared with the CK and NK, soil organic phosphorus contents were significantly increased by 52.3% and 47.8% for the M, and 34.7% and 30.6% for the NPKM, respectively. The available phosphorus contents in the M was 34.2 and 31.0 times of that in the CK and NK, respectively. The available phosphorus content in the NPKM was 25.3 times and 23.0 times of that in the CK and NK, respectively. Besides, the contents of labile organic phosphorus, moderately labile organic phosphorus, moderately resistant organic phosphorus and highly resistant organic phosphorus were significantly increased for the M and NPKM, compared with the CK. In comparison with the CK, NK and NPK, organic fertilizer application (M and NPKM) significantly stimulated the abundances of bacteria, fungi, and phoD-harboring microbes, and the activity of ALP (P < 0.05). In addition, soil organic phosphorus fractions were significantly and positively correlated with the phoD-harboring microbes (P < 0.05). There were significant (P < 0.05) positive correlations between labile Po, moderately resistant Po, highly resistant Po and ALP. The effect of phoD-harboring microbes and ALP on the organic phosphorus fractions was in the order of highly resistant Po > labile Po > moderately resistant Po > moderately labile Po. Together, the application of organic fertilizer could increase the contents of soil organic phosphorus and different organic phosphorus fractions, the abundances of bacteria, fungi and phoD-harboring microbes and the activity of alkaline phosphatase.