Influence of the methods of treating soil in planting hole on the growth of young chestnut trees

Abstract

This experiment was carried out to study the effect of methods of treating soil in planting hole on the current year growth of young chestnut trees planted in the hole. Large planting holes of 120cm in diameter and 90cm in depth were dug and: refilled with the soil in the following procedure.
Plot 1. Each layer of soil was returned to its original position: surface soil to the top layer, subsoil to the bottom.
Plot 2. The surface soil was placed in the bottom of the hole and the subsoil in the top.
Plot 3. The hole was refilled with the mixture of surface soil and subsoil.
Plot 4. The hole was refilled with the surface soil only.
Plot 5. Large holes were not dug. Young trees were set in the small holes just large enough for planting the trees.
A one-year-old chestnut tree (var. Ginyose, a leading variety in Japan) grafted on free stock was planted in the center of each hole.
The measurement at the end of current growing season revealed that trunk circumference was largest in Plot 1, followed by Plot 4 and 5, 3 and 2 in the order. It continued to increase until later in the season in Plot 1 and 4 than in the other plots. Total shoot length was longest in Plot 1 and 4, medium in Plot 3 and shortest in Plot 2 and 5. Shoot elongation ceased earliest in Plot 2 and 3, later in Plot 4 and 5, and did not stop by late fall in Plot 1. The top fresh weight after leaf fall was heaviest in Plot 1, followed by Plot 4, 5, 3, and 2 in the order.
One representative tree each from Plot 1, 2 and 3, respectively was excavated to observe its root system. Roots in Plot 1 penetrated to the deepest layer, and roots in Plot 3 to the shallowest, while there was no significant difference in the extent of lateral spread of root system among the plots.
Leaf samples were collected four times during the growing season for leaf analyses. Little difference was found in N and P contents among the plots, but a positive correlation was found between K content in the leaves and growth.
Chemical properties of each layer of the soil were determined, and porosity of the soil in the planting holes was measured.
From these data it is suggested that the growth of young chestnut trees was affected not only by the physical properties of soil but also by its chemical properties, and poor growth in the current year in the plots, where subsoil was brought to the top layer, might be due to the poor fertility of that layer.