Unchecked weed growth throughout growing period caused 52% reduction in tuber yield of potato. Weed-free condition beyond 45 days had no significant effect on tuber yield of potato. The critical period of crop-weed competition was between 15-45 days after planting (DAP) during which weed-free maintenance would be required for achieving the maximum tuber yield of potato under vertisol. The highest tuber yield of potato (17.90 t ha") was recorded with N120P60K60 under low weed pressure, while the lowest (4.07 t ha") with NoPoKo under high weed pressure, which indicated that maximum fertilizer use efficiency (49 kg tuber yield kg" nutrient applied) could be obtained in the absence of weed competition. However, per cent increase in tuber yield of potato with increasing levels of fertilizer was more pronounced under high weed pressure compared to low weed pressure.