AUTHOR=Gato Isabela Martins Bueno , Oliveira Carlos Eduardo da Silva , Jalal Arshad , Moreira Vitória de Almeida , Hashem Amr H. , de Lima Bruno Horschut , Leite Gabriel da Silva , Al-Askar Abdulaziz A. , Freitas Leandro Alves , AbdElgawad Hamada , Ferreira Selton Vinicius Domingos , Santana Leticia de Jesus , Bastos Andréa de Castro , Galindo Fernando Shintate , Zoz Tiago , Teixeira Filho Marcelo Carvalho Minhoto 

TITLE=Nitrogen uptake, grain yield, and oil concentration of dwarf castor beans under nitrogen rates and inoculation of rhizobacteria in grasses–legumes rotation

JOURNAL=Frontiers in Microbiology

VOLUME=15

YEAR=2024

URL=https://www.frontiersin.org/journals/microbiology/articles/10.3389/fmicb.2024.1451514

DOI=10.3389/fmicb.2024.1451514

ISSN=1664-302X

ABSTRACT=<sec><title>Introduction</title><p>Plant growth-promoting bacteria (PGPB) have been primarily studied for atmospheric nitrogen (N) fixation but they also have the capacity to improve nutrition and yield of crop plants.</p></sec><sec><title>Methods</title><p>Therefore, the objective of this research was to investigate the effects of inoculation with PGPB in association with different N rates on N uptake, grain yield, and oil concentration of dwarf castor beans in succession to legumes and grasses in Ilha Solteira, Brazil. The treatments consisted of N rates (0 to 180 kg ha<sup>−1</sup> of N) and inoculation with three plant growth-promoting bacteria (<italic>Azospirillum brasiliense, Bacillus subtilis</italic>, and <italic>Pseudomonas fluorescens</italic>, applied by leaf) and a control with no-inoculation.</p></sec><sec><title>Results</title><p>The grain and oil yields of castor beans were increased by 20 and 40% at a rate of 103 kg ha<sup>−1</sup> of N in succession to grasses as compared to without N application. In addition, the grain yield of castor bean after legumes was increased by 28, 64, and 40% with estimated rates of 97, 113, and 92 kg ha<sup>−1</sup> of N in combination with inoculations of <italic>A. brasilense</italic>, <italic>B. subtilis</italic>, and <italic>P. fluorescens</italic> as compared to without N application, respectively. Shoot, grain, and total N uptake were improved with foliar inoculation of <italic>A. brasilense</italic>, <italic>B. subtilis</italic>, and <italic>P. fluorescens</italic> at the N rates of 45, 90, and 135 kg ha<sup>−1</sup>, respectively.</p></sec><sec><title>Discussion and conclusions</title><p>Topdressing of N at the rate of 103 kg ha<sup>−1</sup> and foliar inoculation in succession to grasses and 180 kg ha<sup>−1</sup> of N without the effect of foliar inoculation in succession to legumes are recommended for higher grain and oil yield of castor beans. Foliar inoculations with <italic>A. brasilense</italic>, <italic>B. subtilis</italic>, and <italic>P. fluorescens</italic> increased grain yield under reduced use of N fertilizer by 44, 37, and 49% in dwarf castor cultivation in succession to legumes, potentially contributing to sustainable agriculture.</p></sec>