伸長期の追肥と成熟期の落水とが水稻の成熟に及ぼす影響
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概要
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1. Two varieties of the rice plant, an eary and a late, were grown in containers, which were filled with about 10 kg. of loann and applied 4.7 gm. of ammonium sulphate, 6.3 gm. of superphosphate and 1.8 gm. of potassium sulphate. Applying them the following treatments, their effects on the ripening of rice were studied: I. I rrigated floodedly in the usual way (Control). II. Irrigated in the same way as in I, and besides the fertilizers shown above, 2 gm. of ammonium sulphate was applied on Aug. 22. III. Irrigation water was drawn off after the middle of the ripening period. IV. Irrigation water was withdrawn after the heading. V. Treated in the same way as in IV with regard to irrigation and as in II as to the application of fertilizers. The results are shown in the table p. 176-177. 2. It being the fifth and the seventeenth day before the first heading for the early and the late variety respectively when 2 gm. of ammonium sulphate was applied, the effect different according to the growth condition of the both varieties as stated bellow: a) For the early variety, the fertilizer being applied only five days before the first heading, no increase was obtained not only in the number of ears, but also in that of spikelets. But the nutritive condition of the plant appearing to be improved by this fertilizer, the ratio of fertility (the ratio of the number of ripe grains to that of spikelets) was raised, grains ripened more fully and hence the yield of unhulled grains was increased. b) For the late variety, the fertilizer applied seventeen days before the first heading was effective to increase the number of heading tillers and hence that of spikelets. These increased tillers would have been destined to death without heading, if no fertilizer had been given at this time. Because these tillers headed later and thus elongated the heading period about ten days comparing with the control. Although no increase was observed in the ratio of fertility, the yield was increased more markedly than for the early variety on account of the large number of spikelets and more fully ripened grains. 3. Although no effect of the fertilizer was detected on the specific gravity of the unhulled grain as in the case of wheat, the nitrogen content was raised markedly. 4. Flooded water was withdrawn through the LIVINGSTON auto-irrigator cones, which had been fitted up before the sowing, and after that the time the plants were auto-irrigated by this apparatus, inserting a mercury column 5 cm. long between the cones and the water reservoir. Thus the water content of the soil, whose hygroscopic coefficient determined by the American method, was about 5 per cent. fluctuated between 12 and 19 per cent., for the apparatus was unable to supply the loss when the plants transpired very vigorously. 5. When flooded water was withdrawn at the heading time, the ratio of fertility was lowered, the ripening of grains was impeded, and thus the yield was decreased. The withdrawal of water at the middle of the ripening period decreased the yield by reducing the ratio of fertility, though any decrease in the weight of individual grains was scarcely detected. The reduction in the yield was more conspicuous for the early variety than for the late. This appeared to be due to the fact that for the early variety water was withdrawn at the season of higher temperature and the water content of soil was reduced by higher transpiration. 6. The withdrawal of water was not effective on the specific gravity of the unhulled grain, but the nitrogen content was raised markedly. 7. The effect of the withdrawal of water was more conspicuous to reduce the yield in the case where no fertilizer was applied in the shooting stage than in the case where fertilizer was given.1. 水稻及び陸稻をワグネルのポツトに共に湛水して曹通に栽培し, 之に後記するが如き操作を加へることによつて, 伸長期の追肥と成熟期の落水とが成熟に及ぼす影響に就て觀察した。2. 追肥は共に八月二十二日硫酸アムモニア 2gm. を施したのであるが, 供用の水稻と陸稻とでは熟期を異にした關係から, 其等の成育状態よりすれば, 兩者に對して甚だしく時期を異にして追肥した結果になり, 從つて其の影響も兩者で著しく異つたものになつた。即ち: a) 出穗初に先つこと 17 日に追肥したことになつた水稻に於ては, 追肥により穗數は増加し, ――此の増加したものは無數分蘖となるべきものが追肥によつて出穗するに至つたものと見るべく, 此等の出穗は後れた爲, 出穗初は標準顧と同じでも出穗期間はそれだけ延長された。――之によつて螽花數は増加した爲, 稔實歩合には差がなかつたが, 結局の稔實粒は増加し, 充實もよくなつて完全玄米の千粒重も増して收量は著しく増大された。b) 陸稻に於ては追肥は出穗初に先つこと 5 日前に施用されたことになつて, 穗數には勿論, 螽花數にも殆ど影響がなかつたが, 稔實歩合は高められて稔賓粒數を増し種實の充實も亦多少よくなつて, 收量を増加した。併し收量の増加率は水稻に及ばなかつた。3) 追肥は種貴の含窒素量を増したが, 比重には殆ど影響がなかつた。4) 落水は LIVINGSTON 式の素燒圓錐形の自働灌水器を通して行ひ, 爾後此の裝置により灌水し, 以つて土壤の水分量を一定に保つことにした。併し蒸散の餘り盛な時期に於ては灌水器は蒸散による消失水分縫を十分補給し得ず, 爲に落水の時期の異なるに從ひ各區の間に多少の藻を生じた。落水は水稻及び陸稻の雨者に對し, 共に出穗期と出穗期乃至收穫期の半頃との二期に行つた。而して落水の成熟に及ぼした影響は次の如くであつた: a) 出穗期に落水したものでは稔實歩合は低下し, 種實の充實は阻碍されて玄米の千粒重は輕くなり, 從つて放量は甚だしく減少した。b) 後に落水したものでは稔實歩合は低下して收量は減少したが, 玄米の千粒重には著しき景響がなかつた。c) 落水は種實の窒素含有量を高からしめたが, 其の比重には殆ど無影響であつた。d) 落水による減收率は早生であり從つて蒸發の盛な頃落水することになつた陸稻に於ける方が之と反對の水稻に於けるより著しかつた。e) 落水の影響は無追肥のものより追肥したものに於て不顯著であつた。
- 九州帝國大學農學部の論文
- 1932-10-00
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