MSc

An experiment was conducted at the Instructional Farm attached
to the College of Agriculture, Vellayani during December 1998 - April 1999
with the objectives of finding out the role of bioinoculants viz. arbuscular
mycorrhizal fungi (AMF) and phosphate solubilising microorganisms (PSM) in
improving the phosphorus use efficiency and productivity in vegetable cowpea
var. Sharika. The experiment was laid out in 3 x 4 + 2 factorial randomised
block design with three replications. The treatments included three levels of
microbial inoculants and four levels of phosphorus along with two control
treatments.
The study revealed that crop failed to show a significant response
to the use of bioinoculants and phosphorus levels in a soil with low available
nitrogen and medium phosphorus status. Biometric characters except length of
vine at vegetative stage was influenced by phosphate solubilising
microorganisms as well as dual application of PSM and AMF. Phosphorus
application as well as interaction effect did not show a positive response on
growth parameters except LAI at harvest stage where in interaction effect was
significant.
Bioinoculants and phosphorus application exerted a profound
influence on root length and volume. Dual inoculation of AMF and PSM
significantly improved root length and volume. Phosphorus application at all

levels improved root mass where as maximum root length and volume were
reco;ded at P2 level. Interaction effects were significant only with respect to
root volume and root mass. Mycorrhizal colonisation percent was highest with
M3P2 (AMP + PSM + 15 kg P20S ha-I) and showed a decreasing trend with
higher doses of phosphorus.
Microbial inoculants showed only limited role in improving yield
and yield attributes. In general, crop responded positively to phosphorus
application only up to 30 kg P20S ha-I but it was on par with 15 kg P20S ha-I.
Among the interaction effects, dual application of AMP + PSM along with 30
kg P20S ha-1 gave the highest yield. The effect of microbial inoculants in
promoting growth and yield of crop was found to decline in the presence of
higher doses of applied phosphorus.
Quality characters of pod viz. protein and fibre content were
significantly improved by bioinoculants and graded doses of phosphorus. Dual
inoculation of AMP and PSM significantly increased protein content as well as
reduced fibre- content of pod .
. Available nitrogen content in soil after harvest did not show any
significant variation among treatments but bioinoculants significantly
improved residual K20 content in soil. Available P20S content at vegetative,
flowering and harvest stages recorded higher values compared to initial status.
Treatments M3 and P2 recorded the maximum available P20S content at
vegetative and flowering stages. But at harvest stage, lowest residual P20S

content was recorded at P3 level indicating higher uptake by the crop at later
stages. Interaction effects were significant with respect to P20S content only at
vegetative stage.
The results of economic analysis revealed that the net income
and benefit-cost ratio was maximum by dual inoculation of arbuscular
mycorrhizal fungi and phosphate solubilising microorganisms along with a
phosphorus level of30 kg P20S ha-I.