Inoculation with Azospirillum brasilense reduces fertilizer needs in maize

Maize requires nitrogen (N) fertilizers, which are expensive, in short supply in many countries, and can pollute the environment. Scientists tested an alternative method of fertilizing maize that reduced N fertilizer by inoculating the maize at sowing with two strains of the bacterium Azospirillum brasilense: one that synthesizes phytohormones and one that fixes atmospheric N.

The researchers conducted 30 field trials over 10 years in the main producing regions of Brazil. They compared the performance of uninoculated plants topdressed with 100% of the N fertilizer with inoculated plants that received 75% of the fertilizer. They found that both sets of plants produced the same amount of maize. The study demonstrated inoculation’s positive effects under varying conditions, including different grain yield levels, climates, soils, and amounts of soil organic matter.

Performance of the inoculated fields was attributed to better root growth, which increased the N fertilizer use efficiency and reduced both nitrate losses and greenhouse gas emissions. The inoculation, per hectare, reduces costs by US$15 and CO₂ emissions by 236 kg equivalents. Inoculation with plant growth-promoting bacteria represents an important strategy for growing maize both productively and sustainably.