竹類の生育におよぼす珪酸の影響について

Abstract

竹類の生育におよぼす珪酸の影響について検討を加えた｡ 実験はまず竹類による珪酸吸収について調べたが, その結果 1 竹, ササの類はいずれも非常に大量の珪酸を吸収する性質をもっており, またこの吸収された珪酸の大部分は葉部に蓄積されることがわかった｡ 2 マダケ, モウソウチクについて, その吸収の季節的傾向を調べた結果, 両竹種はともに新葉の発生する6月から秋にかけての期間に珪酸を大量に吸収し, 冬期間は大体平衡に達していることがわかった｡ また同じ竹林内の立竹の葉の珪酸含量は稈の太さや竹令と関係なく, ほぼ一定であることがわかった｡ 3 さらに竹林生産力の優劣と, その竹葉中の珪酸含量との関連について調べた結果, 明らかに優良林は, 不良林に比べて, その竹葉の珪酸含量が高いことが判然として認められた｡ このことは優良林ではその土壌からの有効態珪酸の供給力が大きいと考察され, 同時に珪酸成分の供給が竹類の生育に好影響を与えていることが明らかである｡ また珪酸成分は病害に対する抵抗性を強める作用があるように思われた｡ つぎに珪酸質肥料の施与が竹類の生育におよぼす影響について, オカメザサとマダケ林において試験した｡ 試験はいずれも無肥料区, 三要素 (N, P, K) のみの施肥区, 三要素に珪カルを併施した区の三区を設け, その成長量を比べて調査したが, その結果は次のようであった｡ 1 オカメザサを用いて2カ年間継続して試験した結果, 珪酸の併施区は三要素のみの施用区に対して約2倍, 無肥料区に対しては約10倍の生長量 (生重量として) を示し, 明らかに珪酸成分の施用効果が認められた｡ 2 マダケ林において3カ年継続して試験した結果, 珪酸の併施区は三要素のみの施用区に比べて約20%から50%, 無肥料区に比べて約2倍の生長量 (新竹の束数) の増加がみられ, オカメザサの場合と同様に明らかに珪酸成分の施用の効果が認められた｡ また珪酸を併施した区に生育した立竹の稈は三要素のみの施用区に生育した立竹の稈に比べてかなり硬さを増して強剛になっていることが認められた｡ つぎにこれらの処理区に生育した立竹の含水率と, 2~3の養分要素を定量してその吸収状態の違いを調べた結果, 珪酸の併施区の立竹の含水率は他に比べて低いことがわかった｡ また三要素区の立竹は特に窒素含量が高いが, 珪酸併施区の立竹の窒素含量は無肥料区と同程度にまで下がっていることが認められた｡ これらのことが稈を強剛にしている原因となっていると思われる｡

We have investigated the effect of silicic acid on the growth of bamboos. This report consists of two investigations. In the first investigation was examined the absorption of silicic acid (SiO2) by bamboos and sasas. These results were shown in Tables 1--5, and Figs. 1--3. The outline of these results are as follows: ---- 1. The genera of bamboos and sasas had the character absorbing a great quantity of SiO2. And most of the absorbed SiO2 seemed to accumulate in the leaf. 2. Seasonal changes of SiO2 absorption by MADAKE (Phyllostachys reticulata) and MOSOCHIKU (Phyllostachys edulis) were as follows: -- In these species a great quantity of SiO2 was absorbed from June to November. And in winter its contents in the leaves were constant. In the same bamboo grove, contents of SiO2 in the leaves were generally constant negardless of the size and age of the culm. 3. Investigation on the correlation between the productivity of bamboo grove and the contents of SiO2 in the leaf indicated the following results. It was distinctly recognized that the SiO2 contents in the leaves in a good grove is higher than that in a poor grove. This recognition should prove the following. The soil in a good grove has a large suppliement power of the available SiO2. And SiO2 has a good effect on the growth of bamboos. And it seemed that the SiO2 also had the function to increase the resistance of bamboos to injury by disease. Secondly, the effect of silicate fertilizer on growth of OKAMEZASA (Shibataea Kumasaka) and MADAKE was examined. In these investigations, the experimental plots were classfied as follows; ---- Lot 1. Non treatment plot (no fertilizer) Lot 2. Three element plot (N. P. K. supplied) Lot 3. Three element + calcium silicate plot (N. P. K. Si. supplied). Three elements have been supplied as ammonium sulphate, superphosphate of lime and potassium sulphate. These results were shown in Tables 6--7, and Figs. 4--5. The outline of these results are as follows : ---- 1. The investigation on the growth of OKAMEZASA for two years showed: The growth amounts (fresh weight) in the three element + calcium silicate plot had about two times as much as in the three element plot, and had about ten times as much as in the non fertilizer plot. The effect of calcium silicate was clearly proved. 2. The investigation in MADAKE grove for three years showed: The growth amounts (bundles of new culms) in the three element + calcium silicate plot were about 20--50% more than those in the three element plot, and had about two times as much as in non fertilizer plot. The culms in the three element + calsium silicate plot were harder than those in the three element plot. Therfore, it was also proved that calcium silicate has a good effect on the growth of MADAKE.