The objective of this study was to compare the effects of previous crop residue (wheat vs. lentil), tillage (reduced tillage vs. no-tillage) and nitrogen source (rhizobial inoculant and fertilizer-N application) on nodul formation, dry matter accumulation and seed yield of double crop soybean. The experiment was laid out as split-split plot with three replications. According to results obtained from the study, previous crop residue affected seed yield, and seed yield after cultivation of lentil was higher than after wheat. Nodul nitrogen content decreased at the reduced tillage, while nodule dry matter and seed yield increased compared to no-tillage system. Rhizobium inoculation alone produced the highest seed yield. However, the addition of N-fertilizer to inoculated soybean did not improve seed yields when compared with inoculated only treatment. This research demonstrates that applying rhizobium inoculation in no-tillage system under lentil residue has the potential in increase nodulation and seed yield of soybean grown double-cropping system.