Agronomic performance of plant growth-promoting microorganisms and nitrogen sufficiency index in common bean

Abstract

This work aimed to assess Rhizobium tropici, Azospirillum brasilense, and Trichoderma asperellum co-inoculation effects, besides N-fertilizer supplementation as determined by the nitrogen sufficiency index (NSI) on the development of common bean. Field trials were carried out in a randomized block design with four replicates at three different locations. Treatments consisted of sole or combined inoculation of R. tropici, A. brasilense, and T. asperellum, besides N-fertilization. Seeds were inoculated with R. tropici and/or T. asperellum using 10 g of each inoculant kg−1 of seed. At the phenological stage V2/V3 A. brasilense was inoculated using 300 ml ha−1. Nitrogen sufficiency index (NSI), number of nodules (NN), nodule dry mass (NDM), root dry mass (RDM), shoot dry mass (SDM), number of pods (NP), number of grains (NG), and grain yield (GY) were assessed. NN and NDM were higher under R. tropici, A. brasilense, and T. asperellum co-inoculation. This same co-inoculation provided RDM and SDM similar to the use of 120 kg ha−1 of N. R. tropici, A. brasilense, and T. asperellum co-inoculation supplemented with N-fertilizer at the phenological stage R5, provide NP and NG similar to 120 kg ha−1 N, and to 80 kg ha−1 N supplemented with N at the phenological stage V4. NSI was effective to determine the N needs of common bean. The co-inoculation of two doses ha−1 of R. tropici, three doses ha−1 of A. brasilense and two doses ha−1 of T. asperellum, supplemented with N-fertilizer at phenological stage V4 based on NSI, stimulated growth and yield components of common bean, providing GY equivalent to the N-fertilized treatments.