Effect of Wheat Straw Mulch on Flow Characteristics in Wheat Furrows under Rainfed Condition

Wheat grain yield in semi-arid regions is negatively affected by water deficit resulted by low precipitation and soil and water loss caused by water erosion. Limited information is available on methods of controlling runoff in rainfed furrows. Therefore, this study was carried out to investigate the effects of different levels of wheat straw mulch on flow characteristics in a semi-arid region in west of Zanjan. Five levels of wheat straw mulch including 0, 25%, 50%, 75% and 100% of land surface cover (equal to 0.1.5, 3, 4.5 and 6 ton per hectare) were applied using the randomized complete block design at three replications in a rainfed wheat land. Totally, fifteen, 2m×5m. plots were installed in the field and flow characteristics including the starting time, velocity, shear stress, power and hydraulic radius were determined using a constant flow rate of 2 lit min-1. Based on the results, soil properties and flow characteristics were strongly affected by straw mulch level (p< 0.01). Soil properties (field capacity and infiltration rate) improved by application of straw mulch. Straw mulch also  decreased flow velocity, shear stress, hydraulic radius and runoff volume in the furrows. At the 100% wheat straw mulch level, field capacity (15.6%) and infiltration rate (12.1 cm h-1) increased 74% and 2.4 times in comparison with the control treatment. The runoff volume was 3.7 times less than the control treatment in this level of straw mulch. No significant difference was found between 75% and 100% straw mulch level in improving soil properties and controlling flow characteristics.  This study indicated that application of 75% straw mulch level equal to 4.5 ton per hectare is an effective level to improve soil properties and decrease flow velocity in wheat furrows under rainfed condition.