Differential response of wheat to tillage management systems in a semiarid area of Morocco Rachid Mrabet * Soil Physics Laboratory, Institut National de la Recherche Agronomique, Aridoculture Center, P.O. Box 589, Settat 26000, Morocco Received 16 September 1999; received in revised form 28 January 2000; accepted 28 January 2000 Abstract Low, unreliable rainfall and high evaporation potential in semiarid parts of Morocco, but also inappropriate management of soil resources, produce erratic crop yields and uncertain economic returns. The need to maximize soil water conservation and optimize wheat grain production in Moroccan dryland areas have contributed to the emergence of direct seeding technology in this region. A ®eld experiment was conducted to investigate the effects of no-till, minimum till, traditional and deep tillage systems on wheat yield as well as on water use ef®ciency. The experiment was conducted from 1995 to 1999, under rainfall regimes that varied from as low as 195 mm to 440 mm. Grain yields under no-tillage (2.47 Mg ha 1 ) were equal to those obtained using a chisel plow or deep tillage and superior to yields obtained by rotovating, conventional off-set disking, stubble mulching or subsurface traditional tillage. Water use ef®ciency (6.6±7.1 kg mm 1 ha 1 ) was similar following no-till, deep disking and chisel plowing, while other tillage systems had lower but similar values (varying from 5.4 to 5.9 kg mm 1 ha 1 ). Tillage systems did not differ signi®cantly in terms of total dry matter or straw production and water use. Improvements in no- till drill design, which focus on proper seed and fertilizer placement and which prevent seed and straw being placed in close contact, are needed and may contribute to enhanced wheat yield and biomass under no-tillage. # 2000 Elsevier Science B.V. All rights reserved. Keywords: Direct seeding; No-tillage; Tillage system; Wheat yield; Water use ef®ciency 1. Introduction Water scarcity is the major factor limiting produc- tivity in semiarid Morocco (Swearingen, 1992), but little attention has been given to manipulation of soil for improved use of available water. Wheat is the most commonly grown dryland cereal in this region and is of paramount importance in the national economy. Continuous wheat occupies 30% of the arable lands in Morocco, even though it is grown in a permanently stressed environment. Mean cereal yields are low, even after adoption of fertilizers and appropriate crop cultivars (Shroyer et al., 1990). Agronomic research has for many years faced the need to maintain favor- able `soil tilth' in order to sustain productive agricul- ture (Mrabet et al., 1993; Kacemi et al., 1995). Water conservation research starting in the early 1970s, has focused on the effects of tillage systems, row spacing, seeding rate, rotation (including fallow type) and Field Crops Research 66 (2000) 165±174 * Tel.: 212-3-40-32-18/10; fax: 212-3-40-32-09. E-mail address: mrabet1@altavista.net (R. Mrabet) 0378-4290/00/$ ± see front matter # 2000 Elsevier Science B.V. All rights reserved. PII:S0378-4290(00)00074-5