effect of residue management and tillage method on soil physical properties, water productivity and yield of sugar beets

the effects of soil tillage methods and residue management were studied at miandoab agriculure station during 2003-2005. the experiment design was split block with the main plots devoted to residual management strategies (burning residue, crushing residue by disk, no treatment). subplots were tillage methods (moldboard plowing to 20-25 cm in fall, moldboard plowing to 20-25 cm in spring, moldboard plowing to 20-25 cm in both spring and fall). other operations were identical in all treatments. the soil cone index, percent of residue crushing, percent of residue inversion, percent of seed emergence, crop yield, percent of sugar, depth of root development and percent of soil organic carbon were measured. results showed that tillage and residual management had no significant effect on seed emergence, percent of sugar, bulk density and soil cone index. tillage management had a significant effect on yield and depth of root development. fall plowing and fall-spring plowing treatments produced higher yields and root development (15%, 11%) than did the spring plowing treatment. results also showed that soil organic carbon after harvesting was higher (14%) for the crushed and no treatment categories than for the burned residue treatment. burning residue is not recommended, because this strategy had no positive effect on the parameters and, in some cases, reduced root yield and soil organic carbon. water productivity in moldboard plowing at 20-25 cm in the fall treatment was higher than for the other treatments. water productivity based on root yield was 4.32, 3. 47 and 3.66 kg/m3 for fall plowing, fall-spring plowing and spring plowing treatments, respectively.