Inoculation with growth-promoting bacteria and arbuscular mycorrhizal fungi reduce the demand for fertilizers in lettuce

Abstract

The use of plant growth-promoting microorganisms is an alternative to reduce costs with mineral fertilizers and increase sustainability in agriculture. This study aimed to investigate the effect of co-inoculation with plant growth-promoting bacteria and arbuscular mycorrhizal fungi on the growth and yield of lettuce under reduced NPK fertilization and greenhouse conditions, using five treatments (100 % of fertilization; 50 % of fertilization; 50 % of fertilization + Azospirillum brasilense inoculation; 50 % of fertilization + Rhizophagus clarus inoculation; 50 % of fertilization + co-inoculation), with eight replications. The inoculation with R. clarus increased plant height by 79.5 %, while, for A. brasilense, this increase reached 68 %, as compared to NPK fertilization. The single inoculation of both microorganisms increased the stem mass, but only A. brasilense was associated to the higher number of leaves, although it was not accompanied by an increase in the fresh and dry leaf matter. The co-inoculation increased the leaf fresh matter by 24.6 % and the number of leaves by 25.3 %.

KEYWORDS: Lactuca sativa, Azospirillum brasilense, Rhizophagus clarus.