Conservation tillage practices for winter wheat–fallow farming in the temperate continental climate of northwestern Iran Abbas Hemmat a,* , Iraj Eskandari b a Department of Farm Machinery, College of Agriculture, Isfahan University of Technology, Isfahan 84156, Iran b Dryland Agricultural Research Institute, Maragheh, East Azerbaijan Province, Iran Received 5 October 2003; received in revised form 20 January 2004; accepted 25 January 2004 Abstract Soil water is the most limiting resource for crop growth in dryland areas. Conservation tillage has been proposed as a promising strategy to improve soil and water conservation in these areas. A 3-year field experiment to determine the feasibility of conservation tillage for wheat (Triticum aestivum L.) production was initiated in 1999 on a clay loam (Vertic Calcixerepts) soil in the temperate continental climate of northwestern Iran, with an average annual precipitation of 375 mm. The tests were conducted using conventional (moldboard plow), reduced (chisel plow), minimum (sweep plow) and direct drilling (in standing stubble/total residue) tillage systems. In the first year of the experiment (1999–2000), treatments were applied as pre-seeding tillage on a fall chisel tilled fallowed site, whereas in the second and third years, the tillage treatments were applied during fallow with direct drilling of the following wheat. Wheat grain yields were significantly affected by tillage. The same yield trend was observed for the tillage treatments in all years. Yields under reduced tillage were consistently higher (35%) than yields from conventional tillage. Grain yields under direct drilling were similar to those obtained using the reduced-tillage system and superior to yields obtained by conventional tillage system. The minimum till system applied as pre-seeding or fallow tillage reduced crop yields compared to reduced tillage. The overall results showed that tillage intensity could be reduced to the level of reduced tillage or direct drilling with an increase in crop yields. # 2004 Elsevier B.V. All rights reserved. Keywords: Chisel plow; Direct drilling; Minimum till; Moldboard plow; Reduced tillage; Sweep plow 1. Introduction Winter wheat is an important, well-adapted grain crop under dryland condition of the northwest of Iran. It may be grown in a crop–fallow sequence or in rotation with chickpea (Cicer arietinum L.). In the northwest of Iran, 14 months of fallow begin in July after wheat harvest and continue until wheat seeding in September of the following year. Traditional tillage system during the fallow period comprised grazing of wheat stubble after harvest, tilling the soil with mold- board plow and followed by sweeping in mid-summer of the next year before fall wheat planting. For pro- gressive farmer, in addition to stubble grazing, fallow is maintained by spring moldboard plowing followed by one or two passes of sweeping to prevent weeds. However, no seedbed is prepared before fall planting in either case. Field Crops Research 89 (2004) 123–133 * Corresponding author. Tel.: þ98-311-3913493; fax: þ98-311-3912254. E-mail address: ahemmat@cc.iut.ac.ir (A. Hemmat). 0378-4290/$ – see front matter # 2004 Elsevier B.V. All rights reserved. doi:10.1016/j.fcr.2004.01.019