The effects of crop rotation and fertilization on moisture conserved and moisture use efficiency (MUE) were assessed on a loam soil in the Brown soil zone of southwestern Saskatchewan over the period 1967–1984. Six spring wheat rotations were examined that were either fertilized at soil test recommended rates of N and P, or N or P was withheld according to rotation specifications. MUE in this study was calculated as grain yield divided by sum of 1 May to 31 Aug. precipitation plus soil moisture used between seeding and harvest. In the first fall after harvest 8–11 % of the precipitation received was stored in soil in all rotations. During the first winter 3–5 times as much moisture was stored as was stored in the fall; compared to continuous wheat receiving only P, continuous wheat fertilized with N and P increased moisture storage by 12 mm due to a larger amount of crop residues left in the field. In the first 9 mo of summer-fallow, 33% of the precipitation was stored, but over the entire 21-mo fallow period only 18% was stored. At seeding, fallow-seeded crops receiving P annually had 43 mm more moisture in the 120-cm profile than stubble-seeded wheat that received N and P. Failure to apply P to wheat grown on fallow in the F-W-W rotations reduced spring soil moisture at seeding by about 8 mm. Wheat seeded on fallow retained more moisture in soil compared to wheat seeded on stubble until the shot blade stage, but at harvest and fall sampling there was no difference. At harvest there was no available moisture in the top 90 cm of soil. Wheat made greater use of stored soil moisture in dry years than in wet. Wheat grown on fallow that received P used 102 mm of soil moisture per year; wheat on fallow receiving no P used 93 mm; wheat on stubble receiving N and P used 61 mm and continuous wheat receiving no N used 50 mm. The 18-yr average MUE was as high as 6.9 kg ha−1 mm−1 for wheat on fallow that received P and as low as 5.1 kg ha−1 mm−1 for continuous wheat receiving no N. These values were much greater than those reported 30–40 yr ago for this area and reflect improved crop management and crop varieties now used. The improvement in MUE due to fertilizer was greater in later years due to the cumulative effect of fertilizer on soil quality, crop production and crop residues which enhanced moisture available for use. When efficiency was based on the precipitation received from harvest to harvest continuous wheat receiving N and P had the highest efficiency (3.75 kg ha−1 mm−1) and the 2-yr fallow-wheat rotation the lowest (2.60 kg ha−1 mm−1). Key words: Water use efficiency, WUE, nitrogen, phosphorus and moisture use, summerfallow and moisture conservation