Effects of ridging cultivation on the growth  of Fuji apple trees and the utilization and distribution of ¹⁵N-urea under excessive irrigation

Experiments were designed to explore the effects of ridging cultivation on apple tree growth, utilization and distribution of 15N-urea under excessive irrigation on 4-yearold apple trees (Fuji/SH40/ Malus robusta Rehd). Compared to the flat cultivation under excessive irrigation, the ridging cultivation could increase the activities of SOD and POD to 1.70 times and 1.69 times, decrease the free proline content to 63.60%, and increase the root activity and the fine root growth to 1.44 times and 1.68 times at the spring shoots growth arrest stage. These changes are also found in same pattern at the autumn shoot growth arrest stage. At the spring shoots growth arrest stage, the nitrogen use efficiencies (NUE) with ridge cultivation and flat cultivation are 4.40% and 3.86%, no significant difference existed between the two cultivation ways. The NUEs are 5.16% and 4.02% respectively, but no significant difference. The15N distribution rates in the vegetative organs are higher with ridging cultivation than with flat cultivation, the biggest difference occured in the fine roots, and the differences became increased with the process of the growth.