Minimum tillage and residue management increase soil water content, soil organic matter and canola seed yield and seed oil content in the semiarid areas of Northern Iraq

Intensive tillage-based agricultural system is a major cause of soil deterioration and reduction in agricultural productivity in the semiarid areas of northern Iraq. A two year (2009-2011) field study was conducted in Mosul, Nineveh, Northern Iraq. The objectives of this study were to investigate the effect of tillage and residue management on soil water content (SWC), soil organic matter (SOM) and canola (Brassica napus L.) seed yield and seed oil content. The two tillage systems used were conventional tillage (CT) and minimum tillage (MT). Three levels of wheat residue were incorporated into the soil at 0, 2, and 4 t ha(-1). Soil samples were collected from a depth of 0-15 cm at germination, flowering and maturity of canola from a clay loam USDA classified soil. The greatest overall SWC was observed in MT and 4 t ha(-1) of residue, and the high SWC trend was particularly pronounced in 2010 at the critical period of flowering. In 2011, both 2 and 4 t ha(-1) of residue increased SOM by 14 and 18%, respectively, compared with no residue treatment. Residue treatments showed no significant effect on SOM in 2010. Seed oil content was generally greater in MT and 4 t ha(-1) of residue with an average increase of 10 and 20% compared with CT and no residue treatments, in 2010 and 2011, respectively. In 2010, MT with 4 t ha(-1) of residue resulted in 24% increase in canola seed yield compared with CT without residue. Canola seed yield of the CT with 4 t ha-1 of residue was approximately 1617 kg ha(-1) which was 18% greater than the yield recorded at CT without residue. Thus, appropriate residue management could improve soil quality and agricultural productivity in rainfed semiarid areas using minimum tillage systems. (C) 2014 Elsevier B.V. All rights reserved.