Table 1.

The solubilization efficiency of Azotobacter strains in plate assay for which Pi solubilizing index (PSI) and presence or absences of phosphatase activity are given

Bacterial strain	Pi solubilizing index (PSI) a			Phosphatase activityb,c
	2days	4days	7days	With soluble Pi			With insoluble Pi
				24 h	48 h	72 h	24 h	48 h	72 h
				O1	0	1.7±0.1	2.1±0.1	+	+	+	+	+	+
	O2	1.4	1.5±0.1	2±0.2	+	+	+	+	+	+
O3	0	1.7±0.3	2.1±0.1	+	+	+	-	+	+
O4	2.7±0.2	3.3±0.1	3.5±0.1	++	++	++	++	++	++
O5	1.6±0.1	1.7±0.1	1.8±0.3	+	+	+	+	+	+
O6	1.6±0.2	1.7±0.1	1.9±0.1	+	+	+	+	+	+
O8	1.7±0.3	2±0.1	2.4±0.1	+	+	+	-	+	+
O9	1	1.1±0.1	1.3±0.1	-	-	-	-	-	-
O11	1.1	1.4±0.2	1.6±0.3	+	+	+	-	+	+
O14	2.6±0.4	2.8±0.2	3.2±0.1	-	-	+	-	-	+
O15	1.2±0.1	1.3	1.4±0.1	+	+	+	+	+	+
O16	1.4	1.7±0.1	1.8±0.2	+	+	+	+	+	+
O17	2.4	3±0.3	3.4±0.3	++	++	++	+	+	++
O21	1.5	1.6±0.2	1.7±0.2	+	+	+	+	+	+
O24	1	1±0.1	1.2±0.1	-	-	-	-	-	-
O25	2.2±0.2	2.6±0.2	3	++	++	++	++	++	++
O32	0	1.3±0.2	1.4±0.2	+	+	+	+	+	+
O33	1.1	1.4±0.2	1.5±0.2	-	+	+	-	-	-
O34	1.4	1.4	1.6±0.1	+	+	+	+	+	+
O39	1.7	1.8±0.1	1.8±0.1	+	+	+	+	+	+

^aResults presented are means of three replicates ± standard errors

^bSoluble phosphate is KH₂PO₄ and insoluble phosphate is TCP

^c+ Light blue stain and ++ dark blue stain