Keywords: Tillage system, mulch, nitrogen, weed density, weed dry weight, yield

Performance of wheat crop as affected by conventional tillage and zero tillage in combination with the time of nitrogen application and mulch levels was assessed by conducting a field study at the research block of IAAS, Rampur, Chitwan, Nepal, during 2001/2002. The experiment was laid out in split plot design, comprising 4 levels of time of nitrogen application (1/2 N at sowing + 1/2 N at CRI, 1/2 N at 10 DAS + 1/2 N at CRI, 1/2 N at CRI + 1/2 N at 30 DAS and 1/2 N at 30 DAS + 1/2 N at 40 DAS) and 2 levels of mulch (with and without mulch) in main plots and 2 levels of tillage system (zero and conventional) in subplots and was replicated thrice. Observed data showed that yield and yield attributes were found superior under conventional tillage system. Similarly, mulching showed significantly better effect. Weed infestation (weed density and dry matter) was decreased significantly with the application of mulch and was found the least in conventional tillage system. Difference in the time of nitrogen application affected yield significantly and superior results were found where half dose of nitrogen was applied at sowing or 10 days after sowing (DAS) and half at crown root initiation (CRI) stage. Grain yield was increased by 22% (from 2055 kg/ha to 2497 kg/ha), in conventional tillage system and 35% (from 1937 kg/ha to 2615 kg/ha) with mulching. Similarly, when half dose of nitrogen was applied at sowing or 10 DAS and remaining half at CRI stage gave 13% more grain yield. Combination of conventional tillage with mulch and half dose of nitrogen at sowing or 10 DAS with remaining half at CRI was found an optimum, in terms of yield, This gave an increment in grain yield by 112% and straw yield by 105% with maximum net profit of Rs. 9,728 /ha. Moreover, zero tillage without mulching was not found economically viable.