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Conservation tillage ( 7 30% residue cover) has proven to be very effective in reducing runoff and erosion and in increasing soil water storage. In dryland cropping situations, the latter fact should result in a greater yield potential for conservation than for conventional tillage. In practice, however, this theoretical advantage has not consistently realized. The objective of this study was to determine the influence of tillage and N-fertilization management on growth and yield of maize (Zea mays L.) under dryland conditions in the western Corn Belt (U.S.A.). The experiment was conducted from 1977 through 1983 on a Crete-Butler silty clay loam (Pachic Argiustolls-Abruptic Argiaquolls). Whole-plot treatments were moldboard plow, disk, chisel plow, no-till, disk plus manure and no-till plus manure. Sub-plot treatments were N fertilization (NH4NO3) at 0, 70 or 140 kg ha-1 N. Grain yield and yield components were not affected by the tillage x N-fertilization interaction. The response both to tillage and to N fertilization was influenced by yearly climatic variation. Generally, grain yield was maximum at 90 kg ha-1 N and, in dry years, yields usually declined at N rates > 90 kg ha-1 N. In only one year (1978) did tillage influence yield; the chisel plow treatment produced less grain than the moldboard plow or disk. The no-till treatment did not differ from the mean of the other 3 tillage practices in any year. The interaction of yearly weather variation with phenology and the development of the crop appeared to be a greater determinant of yield than tillage.