Economic evaluation of biological nitrogen fixation in flooded rice cultivation in subtropical lowlands
Alcido Elenor Wander | Maria Laura Turino Mattos
This study aimed to assess the economic viability of biological nitrogen fixation in flood rice cultivation in subtropical lowlands. A field experiment of seven treatments was carried out during the cropping seasons 2015/16, 2017/18, 2018/19 and 2019/20 at the Lowland Experimental Station of Embrapa, in Pelotas, RS, Brazil. The evaluated treatments were: (1) negative control (without N and inoculant); (2) positive control with recommended N-fertilization (120 kg N ha-1, without inoculant) (standard recommendation); (3) inoculant 1 (accessions CMM 174 + CMM 175 + CMM 179); (4) inoculant 2 (accessions CMM 176 + CMM 197 + CMM 205); (5) combination of reduced N-fertilizer doses (90 kg N ha-1) + inoculant 1; (6) combination of reduced N-fertilizer doses (90 kg N ha-1) + inoculant 2; and (7) commercial inoculant [Azospirillum brasilense (strains Ab-V5 and Ab-V6)]. A partial budget was used to compare evaluated treatments with the standard recommendation regarding nitrogen fertilisation. Inoculant 2 composed of bacterial accessions CMM 176 (Rhizobium sp.), CMM 197 (Bacillus sp.) and CMM 205 (Aeromicrobium sp.) combined with reduced mineral nitrogen fertilisation [90 kg N ha-1 (applied in top dressing)] demonstrates the best agroeconomic efficiency in the production of irrigated rice in subtropical lowlands with the cultivar BRS Pampa.
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