Objective Effects of applying an amino acid-enriched urea in fertilizing paddy- and upland-rice cultivations on the seedling growth and soil rhizosphere microbial community were analyzed.

Method A pot experiment applying a regular urea (U) or urea fertilizer enriched with amino acids (AU) to grow rice seedlings under paddy- and upland-cultivations was conducted. Changes in the soil microbial community at day 1, 2, 3, 5, 9, and 14 (i.e., D1, D2, D3, D5, D9, and D14, respectively) were monitored using the Biolog ECO microplate method. High-throughput sequencing was employed to identify the dominant microbes in the soil.

Result AU significantly stimulated the growth of rice seedling roots over U by 9.65% under upland-mode, and by 7.56% under paddy cultivation. On all sampling days, the Biolog ECO microplate average well color development (AWCD) after 96h culture of the microbes in AU-treated soil were significantly greater than those in the soil fertilized with U. And on D5, the most significant 120.97% AWCD increase was observed. Proteobacteria, Bacteroidetes, and Acidobacteria, especially Proteobacteria, were dominant in the AU-treated soil. AU fertilization not only improved the uniformity of rhizosphere soil microbial community but also increased the relative microbial utilization rates on 6 major carbon sources, such as alcohols, acids, and amino acids.

Conclusion The application of AU significantly promoted the growth of rice seedlings as well as altered the microbial community structure enriching the soil fertility.