土壌の各層に於ける肥料の分布と胡瓜及び茄子の成育
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1. Containers of galvanized iron sheet, 29 cm. in diameter and 1 m. in depth, were filled with soil in air-dried and pulverized condition. The soil columns in the containers were separated into four layers, 20, 20, 30 and 30 cm. thick from the surface to the bottom, inserting paraffin wax seals, which allowed the passage of the roots but not water and salt solution. Each layer was autoirrigated after the LIVINGSTON method. Thus the amount of water transpired and absorbed by the plant from each layer could be determined by the loss in the water reservoir of the irrigator. Fertilizers were applied in the following way: (snip) Placing the whole apparatus out-doors and cucumbers and eggplants were grown. Thus the effect of nutrients in different layers on the plant growth was observed. 2. In both plants the plat A showed the best growth, being followed by B, C and D in order, though the difference between C and D was not very conspicuous (Tables I and IV.). These differences could be detected even when the plants were rather young, showing that the roots developed into deep layers and absorbed nutrients there at the early stage of their development. 3. The amount of water absorbed from each layer increased as the plant grew. However, the percentrage of the amount of water absorbed from each layer to the total changed as the plant grew and developed its roots into deeper layers, whose activities were more vigorous than those of the older ones in the upper layers. The behavior of the change in the percentages was different according to the different plats, since the plant grown in the soil column having nutrients in deep layers developed its roots more quickly into those layers. When the plant grew to a certiah stage, however, no marked difference in the percentages could be detected between the plats, and in all plats rather large amount of water were absorbed from deep layers (Tables II and VI.). 4. Although the root systems were somewhat different between those two plants, in both plants the skeleton of the root system consisted of the main tap root and thick lateral roots branching at the upper region, from which fine roots branched very densely. This fact is somewhat different from the observations of WEAVER and BRUNER (3), who have reported that the main part of the absorbing system of these plants is restricted in the upper layer under the field condition, although the tap root or the thick lateral roots developed in deep layers. This is probably due to the fact that in the case of our experiment the soil condition, especially the aeration, was good even in the deep layers. Such development of roots appears to explain the facts stated in the articles 2 and 3 (Figs. 1 and 2). 5. The development of fine roots in each layer seemed to be parallel to the amount of nutrients applied in that layer. The direct relationship, however, could not be detected between the development of the absorbing organ and the amount of water absorbed; that is, in the layer where fertilizers were applied the roots developed very well, but they did not absorb so much water. Hence, the atnount of water absorbed per unit area of the absorbing system was less in the fertilized layer than in the unfertilized one. This fact may be explained as follows: As the osmotic concentration of the soil solution in the fertilized layer is higher and hence resists to the absorption of roots, the plant increases its absorbing area to adapt to this condition. In order to determine whether this explanation is correct or not, however, more experiments would be necessaly.1. 直徑 29 cm. 深さ 1m., の亞鉛引鐵板製の圓筒に土壤を填充し, 之を四層に區分し, 各層には二個の素燒製圓錐形の自働灌水器を裝置することにより土壤の水分量を一定に保つと共に, 土表及び各暦相互の間には薄きパラフィンの層を作りて水分及び養分の移動を妨ぐるも根の通過を自由ならしめた。而して肥料を :A) 各層同量づつ第一乃至第三層に, B) 第一及び第二層に, C) 第一層のみに, 並に D) 半量づつを第一及び第二層に分施するものゝ四區を區別して, 之等に茄子及び胡瓜を栽培し, 植物の成育並に各層よりの水分吸收の模樣に就て觀察した。2. 植物の成育は胡瓜も茄子も共に A が最も良く, 以下 B, C, D と順次に劣り, 而も此の差はかなり早い頃より現はれて, 根の深層に於ける活動は相當早くから植物の成育に影響するものであることを示した。3. 土壤の各暦より植物の吸放する水分量は植物の成育に作ひ増加したが,深い暦ほど根の發育して行くのが晩くなる爲, 各層の吸水量の總吸水量に對する割合は植物の成育に件ひ上層に於て減じ, 下層に於て増加した。而して A, B, C, D と順次成長の晩れる傾あるが故に, 成長に伴ふ各暦の吸水量の總吸水量に對する割合の變化も A, B, C, D の順序で違つてゐた。併し相當成育したものに於ては各層の吸水量の割合には各區の間に大差なく各區共深い層からかなり多量の水分が吸收された。4. 根群 (Root system) は胡瓜と茄子とで多少違つてゐたが, 何れも直根乃至その上部で分岐した太い側根が根群の骨格をなし, 之から分岐する多數の細根により吸收組織 (Absorbing system) を形戒してゐた。而してかゝる細根の發育は WEAVER 等の野外で觀察したものとは異なり, 深い層に於ても極めて可良であつた。之は深い層迄土壤の物理的状態の良好であつたことに原因するものであらう。斯る根の發育は (2) 及び (3) に述べた事實を克く説明してゐる。5. 各層に於ける細根の發育は施肥量と平行し, 施肥した層には多く, しない層には少かつた。而して此の事實は胡瓜よりも茄子に於て特に著しく認められた。斯く細根の發育は施肥量と平行したが, 其の吸水量とは直接の關係なく, 細根の發育可良なる層の吸水が特に多量であるといふ事實は認められなかつた。斯くして各區肥料の分布の異なるに從ひ各層に於ける細根の發育の模樣を異にしたが, (3) の終に述べた如く相當成育したものに於ては各層よりの吸水量の總吸水量に對する割合は各區大差がないといふことになつた。而して施肥した層には根はよく發達しても, 其の吸水量がそれに比例して多くないとすれば, かゝる根の單位吸水面積に對する吸水量は却つて少いといふことになる。
- 九州帝國大學農學部の論文
- 1932-10-00
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