Response of lentil to Rhizobium leguminosarum bv. viciae strains at different levels of nitrogen and phosphorus

Response of lentil (Lens culinaris Medik) to inoculation with 3 local and 1 exotic Rhizobium leguminosarum bv. viciae (lentil rhizobia) strains at different levels of nitrogen and phosphorus (00:00, 20:20, 20:40, 20:60, 20:80, 40:20, 40:40, 40:60 and 40:80 kg/ha as N and P2O5, respectively) was studied. A field experiment was conducted on a soil deficient in nitrogen and available phosphorus that had a very low indigenous population of lentil rhizobia. Percentage strain recovery (nodule occupancy) revealed that the inoculant strains were highly competitive and occupied 71–95% of the nodules. Inoculation had significant benefits for nodulation, biomass, grain yield, nitrogen and phosphorus uptake at all levels of nitrogen and phosphorus. Inoculation with the local strain Lc26 increased yield by 393 kg/ha compared with the uninoculated control. Maximum biomass, and nitrogen and phosphorus uptake were observed where nitrogen and phosphorus were applied at the rates of 40 and 60–80 kg/ha, respectively. The 40:80 kg nitrogen and phosphorus per hectare combination gave the maximum nodule number, nodule dry weight and grain yield (904 kg/ha) with a net return of US$189 as compared to the unfertilised control and there was an income of US$7 for each dollar invested on fertiliser.