Plains of South Asia have led to the depletion of soil organic carbon content and inherent soil fertility
resulting in a serious threat to the sustainability of these production systems. Bioagents like Gluconacetobacter
diazotrophicus and Trichoderma viride have great potential to restore soil fertility and promote
sugarcane growth. Field experiments, therefore, have been conducted to study the integrated effect of
bioagents (G. diazotrophicus and T. viride), Farm Yard Manure (FYM) and fertilizer N on sugarcane rhizosphere,
crop yield and N economy for two crop cycles during 2004–2006 and 2005–2007 crop seasons at
Lucknow, in the middle Indo-Gangetic plain region. Both bioagents could survive and colonize sugarcane
rhizosphere and FYM improved their colonization. Enhanced soil microbial population and microbial
carbon (SMC) and nitrogen (SMN) with increasing N level were probably due to more available N in the
soil. FYM/bioagents amendment further enhanced the microbial carbon. The uniform increase in the
fraction of SMC and SMN of total organic carbon indicated that immobilization/mineralization was being
maintained in the soil where enhanced microbial biomass might act later as a source of nutrients.
Bioagents ammended FYM enhanced the uptake of N, P and K in sugarcane at all the levels of fertilizer
N. Itwas mainly due to the enhanced nutrient availability in the rhizospheric soil as the soil organic C and
available N, P and K content increased with the application of bioagents/FYM. A saving of 76.3 kgNha−1
was envisaged by the use of G. diazotrophicus inoculated FYM with marginal (2.4 t ha−1) decline in the
cane yield. Application of T. viride enriched FYM, however, brought economy in the use of fertilizer N by
45.2 kg ha−1 and also increased the yield by 6.1 t ha−1compared to the control treatment. Overall, strategic
planning in terms of an integrated application of these bioagents/manures with fertilizer N will not only
sustain soil fertility but will also benefit farmers in terms of reducing their dependence and expenditure
on chemical fertilizers.