Controlled-release fertilizers combined with Pseudomonas fluorescens rhizobacteria inoculum improve growth in Pinus halepensis seedlings

Abstract

Pinus halepensis seedlings are currently used to regenerate arid Mediterranean regions. Optimized methods for seedling fertilization in nurseries improve plant growth and are essential for successful reforestation. Previously, we showed that inoculation of P. halepensis seedlings with Pseudomonas fluorescensCECT 844 rhizobacteria improved plant growth and N uptake. The aim of this study was to determine the physiological and morphological response of P. halepensis seedlings to a combined treatment including controlled-release fertilization and inoculation with the rhizobacterium P. fluorescens. P.halepensis seedlings were grown in a nursery under well-watered conditions and were fertilized (F), inoculated with P. fluorescens (Ps) or fertilized and inoculated (F x Ps). Growth and water parameters (osmotic potential at both full and zero turgor and modulus of elasticity) were measured in seedlings under each treatment. The total N, P, K, Ca, Mg and Fe contents and concentrations in seedling roots and shoots were also measured. Finally, root growth potential was estimated. F x Ps increased both seedling growth and nutrient uptake compared with the independent treatments. Interestingly, amendment with rhizobacteria had a slight negative effect on osmotic potential and P uptake, which was lessened by combining Ps with F. The present work shows that F x Ps is highly efficient for improving the quality of forest seedlings in nurseries. As such, F x Ps represents a potential alternative treatment that could reduce contaminant emissions and increase microbiota soil regeneration in degraded soils.