Abstract
In this study, two experiments (Experiment 1&2) were conducted to investigate the effects of chisel plowing on soil conditions and nitrogen absorption of maize (Zea mays L.) in upland fields converted from an andosol paddy field. In Experiment 1, two hybrids were planted under two tillage systems (rotary tilling and chisel plowing), and soil physics, soil chemistry and nitrogen absorption of maize were examined. In Experiment 2, the difference in fertilizer distribution between the two tillage systems was examined. In Experiment 1, the soil penetration resistance value at 0–5 cm depth was nearly the same in the two tilling systems, whereas, at 5–20 cm depth it was larger in the chisel plowing system, than in the rotary tilling system. In the chisel plowing system, the percentage of gas phase at 10 and 20 cm depth was lower and that of the solid phase was higher than in the rotary tilling system. Contents of nitrate nitrogen, exchangeable potassium and available phosphorus at the 6-leaf stage were higher in chisel plowing than in rotary tilling at a 0 –10 cm depth, whereas there were no significant differences between the two tillage systems at the maturity stage. There was no significant difference between the two tillage systems. In Experiment 2, more than 95% of fertilizer was distributed at 0–10 cm in the chisel plowing system, whereas in the rotary tilling system, the fertilizer distribution was almost uniform at 0–20 cm depth. It is concluded that, in the chisel plowing system, penetration resistance was high at 5–20 cm, and furthermore, fertilizer and soil nutrient were concentrated at 0–5 cm at the early growing stage. It is also concluded that chisel plowing allows farmers high-speed work while maintaining nitrogen absorption at the same level as in rotary tilling in an upland field converted from a paddy field.
