Studies on soil health and plant growth promoting potential of Rhizobium isolates

A comperative study of organically and conventionally managed soils under beans was conducted to ascertain the physicochemical and microbiological characteristics of these soils. Average values of physicochemical and microbiological parameters of the rhizosphere soil samples from the selected districts were compared with the bean rhizosphere soils of the organic farm of Sher-e-Kashmir University of Agricultural Science and Technology of Kashmir India. The results revealed that the soil of the organic farm has significantly higher content of organic carbon (1.04%), available Nitrogen, (298.7 kg[ha.sup.-1]) phosphorus (16.72 kg[ha.sup.-1]), potassium (296.30 kg[ha.sup.-1]), dehydrogenase activity (68.7[micro]g TPF/24 hr [g.sup.-1] soil), total viable bacteria (78.90 x [10.sup.6] cfu [g.sup.-1] soil), fungi (48.73 x [10.sup.3] cfu [g.sup.-1] soil), actinomycete (27.20 x [10.sup.3] cfu [g.sup.-1] soil), phosphate solubilizing bacteria (18.30 x [10.sup.5] cfu [g.sup.-1] soil) and mycorrhizal spores (4.10 spores [g.sup.-1] soil) followed by that of district Kupwara rhizosphere soils with organic carbon (0.97%), available Nitrogen (293.0 kg [ha.sup.-1]), phosphorus (15.81 kg [ha.sup.-1]), potassium (252.3 kg [ha.sup.-1]), dehydrogenase activity (62.7 [micro]g TPF/24 hr [g.sup.-1] soil), total viable bacteria (72.60 x [10.sup.6] cfu [g.sup.-1] soil), fungi (45.76 x [10.sup.3] cfu [g.sup.-1] soil), actinomycete (24.3 x [10.sup.3] cfu [g.sup.-1] soil), phosphate solubilizing bacteria (14.8 x [10.sup.5] cfu [g.sup.-1] soil) and mycorrhizal spores (3.8 spores [g.sup.-1] soil). Rhizobium bacteria were also isolated from the effective nodules of the bean plants grown at different places of various districts in Kashmir valley, India. These isolates after identification were screened for the production of IAA, GA and siderophores. The isolate (Rhizobium phaseoli OF) from Organic farm was found most promising by producing 39.20 [micro]l, 162 [micro]l, and 24 [micro]l of IAA, GA and siderophor respectively followed by 37.5 [micro]l, 153 [micro]l, and 21 [micro]l of IAA, GA and siderophor respectively from the isolate obtained from rhizosphere soils of Kupwara district. The isolate (Rhizobium phaseoli OF) was used in combination with three levels of fertilizer nitrogen (0, 20 and 40 kg [ha.sup.-1]) in a field experiment with beans as experimental crop and five replications by adopting RBD design to study the impact on various plant growth and yield attributing features like