Response of two wheat cultivars to inoculation of diazotrophic bacteria in combination with reduced nitrogen fertilisation under field conditions

Abstract

Chemical fertilisers are essential for plant nutrition in attaining desired yields. However, increased cost of fertiliser input has made it impossible for small-scale farmers to properly fertilise their crops for optimum yields. Five bacterial strains originally isolated from no-till agricultural soil were tested as seed treatments for their potential to increase growth and yield of two wheat cultivars, under a low dose of nitrogen fertilisation in repeated split-plot field experiments. Two nitrogen levels (0% and 35%) with and without bacteria treatments were tested. The controls were 100% nitrogen, 0% nitrogen (uninoculated control) and 35% nitrogen control. Wheat yields were 51–96.5% higher than the uninoculated control and 24.7–43.1% higher than the fully fertilised control. Increases in shoot dry biomass were consistent with yield increases and varied with bacterial strain, cultivar used and growing season. All of the bacterial strains tested positive for ethylene, siderophore and indoleacetic acid (IAA) production. Ethylene and IAA production ranged from 28.4 to 51.3 nmol L⁻¹ h⁻¹, and from 2.1 to 14.6 mg mL⁻¹, respectively. The consistency in yield response of wheat to bacterisation in the presence of a low dose of nitrogenous fertiliser indicates that these diazotrophs could be used as a supplement to nitrogenous fertiliser.

Keywords:

• diazotrophic bacteria
• nitrogen-fixation
• phytohormones
• plant growth promoting rhizobacteria
• wheat