Evaluation of potassium application on tomato performance and rhizosphere bacterial communities under negative pressure irrigation of greenhouse-grown

The study investigated the response to five levels of potassium (K) fertilizer addition on tomato (Solanum lycopersicum L.) performance and soil bacterial communities by negative pressure irrigation (NPI) over two consecutive years. The application of K fertilization positively affected tomato performance under NPI, as indicated by increased yield, quality, growth, and nutrients' contents of tomato compared with no K addition treatment. High-throughput sequencing of the rhizosphere soil revealed that K additions significantly affected in the bacterial diversity indices according to Chao1, Ace, and Shannon. K addition significantly increased the relative abundance of Gemmatimonadetes and decreased the level of Planctomycetes. There were very prominent increases in the levels of the genus Opitutus, but reduced the content of Sphingomonas and Bdellovibrio compared with no K addition treatment. Furthermore, application of 150 kg K ha(-1) (K150) was considered to be beneficial for plant growth and rhizosphere bacterial diversity of tomato. The tomato yield under K150 was considerably increased by 58% and 47% compared with no K addition treatment in 2016 and 2017, respectively. The K150 showed the highest K fertilizer utilization efficiency compared with other K treatments, with K contribution rate and K agronomic efficiency reaching 36.7 and 62.9 as well as 32.0 and 53.6 in 2016 and 2017, respectively. Therefore, these findings also demonstrate that K application under NPI not only promotes yield and quality of tomato fruits but also positively affects the rhizosphere microbiome.