Yield response of groundnut (Arachis hypogaea) to dual inoculation and liming of an acid hill Ultisol of Manipur

A field experiment was conducted during the rainy seasons of 2000 and 2001 in an acid hill Ultisol of Manipur with groundnut (Arachis hypogaea L.), to study the efficiency of single as well as dual inoculation with Rhizobium (TAL 1000) and phosphate-solubilizing micro-organism (Bacillus polymyxa Prazowski) in increasing the yield under limed and controlled conditions. Rhizobium alone did not increase the pod and haulm yields significantly, but when inoculated in combination with B. polymyxa increased the nodule weight/plant (0.23 g), pod (1 520 kg/ha) and haulm yields (2 250 kg/ha) and their respective N (65.1 and 61.5 kg/ha respectively) and P uptake (4.98 and 4.63 kg/ha respectively) significantly. B.. polymyxa was effective in solubilizing the insoluble phosphorus of the soil and increased the available P content in the soils by 13.5%. Further, liming increased the efficiency of phosphate-solubilizing microorganism and increased the available P content in the soil by 26.9%. Liming alone increased the nodule weight/plant (71%), pod (36%) and haulm yields (37%) and their respective N (51 and 91% respectively) and P uptake (49 and 50% respectively) significantly. Maximum pod yield of 1 740 kg/ha was obtained with dual inoculation of Rhizobium (TAL 1000) and B. polymyxa coupled with 2.5 tonnes/ha lime compared with the control (992 kg/ha).