Synergistic effects of nitrogen and plant growth-promoting rhizobacteria inoculation on the growth, physiological traits and nutrient absorption of intercropped Eucalyptus urophylla × Eucalyptus grandis and Dalbergia odorifera

Abstract

Key messageLegume/nonlegume intercropping systems equipped with moderate nitrogen (N) application and PGPR inoculation could be exploited in eucalyptus growing areas and degraded land as an ecologically sustainable system to avoid excessive fertilization and enhance nitrogen use efficiency.Hazardous nitrogenous fertilizers in eucalyptus monocultures are challenging for the balance between eucalyptus wood production and ecological service functions. To assess whether plant growth-promoting rhizobacteria (PGPR) inoculation coupled with N application may improve plant growth by increasing biomass, photosynthesis, soil nutrient supply, and nutrient uptake capacity in the intercropping system. A pot experiment was performed to evaluate the synergistic effects of N application and N-fixing PGPR on growth, physiological parameters, N accumulation and nitrogen use efficiency (NUE) in intercropped Eucalyptus urophylla × Eucalyptus grandis (E. urophylla × E. grandis) and Dalbergia odorifera (D. odorifera). N fertilization positively influenced the plant height, dry matter yield, photosynthetic characteristics, N accumulation and nitrate reductase activity of E. urophylla × E. grandis under both inoculations. The growth and physiological traits of D. odorifera improved under the N2 (6 g N pot−1) application level. E. urophylla × E. grandis inoculated with Rhizobium japonicum IOC 113-2 showed higher values for plant height, biomass accumulation, N accumulation and photosynthesis with N fertilization, but the growth and physiological parameters of D. odorifera responded differentially to different inoculation treatments. The results demonstrated that an appropriate N supply in combination with N-fixing PGPR inoculation of legumes could increase nutrient absorption, NUE and yield advantages in intercropped E. urophylla × E. grandis and D. odorifera; thus, this method could be recommended as an alternative planting system under N-limited conditions in agroecosystems.