Bioinoculant production composed by Pseudomonas sp., Serratia sp., and Kosakonia sp., preliminary effect on Allium cepa L., growth at plot scale/Produccion de un bioinoculante compuestos por Pseudomonas sp., Serratia sp., y Kosakonia sp., efecto preliminar sobre el crecimiento de Allium cepa L. a escala de parcela/ Producao de um bioinoculantes composto por Pseudomonas sp., Serratia sp., e Kosakonia sp., efeito preliminar na Allium cepa L., crescimento em escala de lote

Phosphorus (P) is an essential nutrient for plant's development, and its deficiency restricts crop yield. To meet P requirements in agricultural settings, a low-cost culture medium (MT11B) was designed in which a bioinoculant was produced consisting of three bacterial isolates capable of solubilizing P from phosphoric rock (PR). Pseudomonas sp., Serratia sp., and Kosakonia sp. exhibited P solubilization in SMRS1 agar modified with PR (5.0 g[L.sup.-1]), as source of inorganic P. Sowings by isolation were made of the three bacteria on DNAse- and Blood-agar to rule out pathogenicity. At the interaction tests, no inhibition halos were observed; demonstrating there was no antagonism among them, thus they were used to constitute a consortium. Growth curve (12 h) in MT11B demonstrated consortium grew in presence of PR, brewer's yeast hydrolysate, and glucose at concentrations (2.5g[L.sup.-1]) fourfold lower than those in SMRS1 (10.0g[L.sup.-1]); obtaining phosphate solubilizing bacteria of (10.60 [+ or -] 0.08) [log.sub.10]CFU[mL.sup.-1] and, at 6 h of culture, acid and alkaline phosphatase enzyme volumetric activities of (2.3 [+ or -] 0.8/ UP and (3.80 [+ or -] 0.13/ UP, respectively. The consortium, releasing phosphorus at a rate of (45.80 [+ or -] 5.17) mg[L.sup.-1] at 6h of production, was evaluated as bioinoculant in onion plots for five months. Plants receiving a treatment that included 500 mL (10 x [10.sup.7] CFU [mL.sup.-1]) of bioinoculant plus 100 kg [ha.sup.-1] of an organic mineral fertilizer exhibited the highest determined response variables ((170.1 [+ or -] 22.2/ mm bulb height, (49.4 [+ or -] 6.5/ mm bulb diameter, (9.0 [+ or -] 1.8/ g bulb dry weight, and 15.21 mg[bulb.sup.-1] total phosphorus) (p < 0.05).