Manure and mineral fertilization change enzyme activity and bacterial community in millet rhizosphere soils.

Fertilization is a key agricultural practice for increasing millet yields and influencing soil properties, enzyme activities and rhizosphere bacterial communities. High throughput Illumina sequencing of the 16S rDNA was applied to compare the bacterial community structures and diversities among six different soil samples. The experiments involved the following: no fertilizer (CK), phosphate (P) and potassium (K) plus organic manure (M) (PKM), nitrogen (N) and K plus M (NKM), NPM, NPK and NPKM fertilization. The results showed that the NPKM fertilization of the millet field had a maximal yield of 3617 kg ha-1 among the six different treatments. The abundances of the Actinobacteria and Bacteroidetes phyla, especially the Devosia, Mycobacterium, Opitutus and Chitinophaga genera, were higher in NPKM than those in the other samples. Redundancy analysis showed that the soil organic matter (SOM), available phosphorus (AP), and urease (UR) activity were significantly correlated with bacterial communities, while SOM and AP were strongly correlated with soil enzyme activities. Pearson's correlation showed that the available nitrogen was strongly correlated with Devosia and Mycobacterium, and SOM was strongly correlated with Opitutus and Chitinophaga. Besides, catalase was significantly related to Iamia, the UR was significantly related to Devosia, phosphatase was significantly related to Luteimonas and Chitinophaga. Based on the soil quality and millet yield, NPKM treatment was a better choice for the millet field fertilization practices. These findings provide a better understanding of the importance of fertilization in influencing millet yield, soil fertility and microbial diversity, and they lead to a choice of scientific fertilization practices for sustainable development of the agroecosystem.