Response of Different Crops to Conservation Tillage in Semi-Arid Mediterranean Conditions.

Zero-tillage, which is widely used in dry areas of many countries, is not well known in West Asia. This study evaluated whether performance of various crops and soil organic matter (SOM) accumulation would be different under various tillage practices. The rainfed field experiments in a strip-plot design with four replicates were conducted in the semi-arid, central Bekaa Valley of Lebanon for five years. There were three tillage treatments: conventional (CT), minimum (MT), and no tillage (NT). Crops studied were barley (Hordeum vulgare L.), chickpea (Cicer arietinum L.), and safflower (Carthamus tinctorius L.). The study was divided into two periods: 2005-2006 and 2006-2007 (1^st period) and 2008-2009 and 2009-2010 (2^nd period) for comparison. Samples for SOM analysis were collected at different depths in 2011. Period-by-tillage-by-crop interaction was significant for grain yield. In the 1^st period, barley yielded more under CT than NT and MT, safflower yield was higher under NT than MT, but chickpea yield was similar under the three tillage practices. However, tillage by crop interaction was not detected in the 2^nd period. Period by tillage interaction was significant. In the 1^st period, grain yield was higher under CT than MT, but no difference existed in the 2^nd period. There were no significant differences among the tillage practices (2971, 2908, and 2681 kg ha^-1 for CT, NT and MT, respectively) and between the periods. For SOM, significant difference among tillage practices existed only at 5-10 cm depth (NT 5.3%, MT 5.1%, and CT 5.1%; LSD=0.17%), and rotation by tillage interaction was significant only at 0-5 cm depth. In conclusion, unlike barley and safflower, chickpea grain yield was consistently not affected by tillage practices. Besides, mean grain yield of the three crops and SOM were similar under the three tillage practices over a medium term in a semi-arid Mediterranean location.