Effects of tillage on bulk density and soil moisture content in wheat-fallow rotation under dry conditions

In the arid and semi arid region of Iran, conventional tillage is mainly used(Moldboard plowing followed by two disc harrowing) for wheat production. Such a tillage system requires a high energy input and may also cause water loss and long-term soil physical degradation. This field study was conducted under dry conditions to determine whether or not the reduced tillage systems altered the bulk density and soil moisture content. Thus, five tillage treatments (T1-moldboard plow + disc harrow as the conventional method, T2- chisel plow + disc harrow, T3- moldboard plow without inversion page + disk harrow, T4- power harrow, and T5- sweep plow + disk harrow) were studied during the three year period (2004 to 2007) in soils with silty clay loam texture. Soil moisture in four depths (0-10, 10-20, 20-30 and 30-40 cm) was measured at the flowering and grain filling stages. Generally, the lowest soil bulk density was obtained by T1 treatment. There were significant differences among tillage methods for soil moisture at the flowering stage (P < 0.05) and T1 treatment had the highest value. There were no significant differences among soil tillage methods for soil moisture at the grain filling stage. Overall, chisel plow + disc harrow treatment was recognized as the best tillage method due to the remains of stored soils at the grain filling stage. Key words: Bulk density, dry conditions, soil moisture, tillage.