Objectives This study examined the root distribution characteristics of young Korla fragrant pear tree from 1 to 6 year old, to provide a theoretical basis for efficient water and fertilizer management.
Methods In a flooding irrigated orchard of southern Xinjiang, Korla fragrant pear trees from age 1 to 6 year old were chosen, and three plants in each age were used as the test materials. A profile of 0−100 cm deep and in semi-diameter of 160 cm was dug under each pear tree trunk. Soil samples were collected every 20 cm for the determination of root length, root surface area, and root volume in different thickness classes, using the WinRHIZO root analysis system.
Results The absorbing root length were dominated in all the pear trees from age 1 to 6 year old, accounting for 86%−95% of the total root length, and the root length increases were significantly higher in 3, 5, and 6 years than in other years. The increase of root surface area was contributed by roots in all the diameter classes. The absorbing roots contributed the most, accounting for 41%−77% of the root surface area, followed was conduction roots (22%−33%). The growth of root volume was mainly due to the coarse roots and conducting roots. The coarse roots grew faster in the 4 and 6 years, while the conducting roots grew faster in the 3 and 5 years, showing asynchronous growth. The root length density of pear trees increased first and then decreased with the deepening of the soil layer, showing a “single peak” pattern, but decreased with the increase of horizontal distance. In the vertical direction, 76.46% of the total root length across the entire sampling profile distributed in 0−60 cm depth in all the ages of trees. In the horizontal direction, 71.93% and 41.62% of root length density distributed within 20 cm in the 1 and 2 years, and kept extending along the horizontal direction with growth years. In 2−4 years, the root density was relatively small, the root growth was characterized mainly by extension and the dense areas was sparsely appeared far from the tree trunk. In the 6 years, the dense root length areas were connected and the root length density became even in the horizontal direction, showing a vertical layered distribution. The absorption roots grew vigorously within 40 cm of the horizontal distance, accounted for over 39.56% of total root length in 1−5 years, so was the main contributor to the growth of root length density in the entire sampling area.
Conclusions Under flood irrigation conditions, Korla fragrant pear in age 1 to 2 year old distributed their root system far from the trunk, having a large growth spaces. The conducting and absorbing roots preferentially occupy a larger soil space. From 2 to 5 years, a dense root system area is formed around the trunk, which is conducive to expanding the range of nutrient absorption space. The dense root system areas of 6-year-old pear trees are connected together and evenly distributed in horizontal direction, and characterized by concentrated distribution in a soil layer of 20−60 cm depth. In the actual production, water and fertilizer management should consider the area beyond 40 cm away from the main tree trunk.
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