Effects of Plant Growth-Promoting Rhizobacteria and NPK Fertilizers on Biochemical and Microbial Properties of Soils Under Ginger (Zingiber officinale) Cultivation

Abstract

For this study, plant growth-promoting rhizobacteria (PGPR) were isolated from soils under ginger and shortlisted based on their nutrient mobilization traits. The promising PGPR (Burkholderia cepacia, Klebsiella sp., Serratia marcescens, and Enterobacter sp.) were either applied alone or in combination with varying rates of NPK fertilizers to determine their effect on sensitive biochemical and microbial properties of soils under ginger (Zingiber officinale Rosc.). The properties studied were soil organic carbon, dissolved organic-C (DOC), and -N, microbial biomass-C (C MIC), -N (N MIC) and -P (P MIC), net N mineralized (N MIN), soil respiration (SR), metabolic quotient ( $$ q_{{CO_{2} }} $$ ) and activities of dehydrogenase (DHA), acid phosphatase (AcP), β-glucosidase (βG), and urease (UR). Results revealed a 24 % increase in mean DOC level in treatments with PGPR + NPK compared to control. Similarly, mean C MIC and N MIC levels were greater by 27 and 71 %, respectively, in treatments involving PGPR + NPK compared to treatments with only fertilizers. Also, combined application of PGPR and fertilizers positively influenced P MIC and N MIN rates compared to sole application of PGPR or NPK. While SR did not vary considerably among the treatments, $$ q_{{CO_{2} }} $$ levels across PGPR + NPK treatments were lower by 15–20 % relative to treatments with only NPK or PGPR. Results also revealed that DHA activity was on an average greater by 49.0 %, UR by 15 %, AcP by 40 %, and βG by 35 % in PGPR + NPK treatments compared to only NPK.