コウウン シンド ナラビニ ハシュ ヨウシキ ノ ソウイ ガ タンスイ ドジョウチュウ チョクハ スイトウ ノ タイトウフクセイ ニ オヨボス エイキョウ

水稲の湛水土壌中直播栽培において,播種様式(散播と条播)並びに耕耘深度(5cmと15cm)が耐倒伏性に及ぼす影響を圃場試験で検討した。耕耘深度15cm区(15cm区)の散播区と条播区の倒伏程度は同程度で,しかも耕耘深度5cm区(5cm区)の散播区と条播区より高かった。5cm区では条播区が低く,最も耐倒伏性が強かった。条播15cm区は,散播15cm区に比べて押し倒し抵抗値と引き抜き抵抗値は高かったが,地上部生育が旺盛であったため散播15cm区と同程度の倒伏を示した。5cm区は,生存葉鞘枚数,押し倒し抵抗値および引き抜き抵抗値から判断して,根の活性や根の物理的強度の向上が倒伏を軽減したものと推察された。しかし,散播5cm区が,条播5cm区よりやや倒伏程度が大きかったのは,株直下に分布する根量が少なかったことによるものと考えられた。The purpose of this study was to clarify the effects of tilling depth (i.e., 5cm and 15cm) and sowing styles (i.e., broadcast and row sowing) on the lodging tolerance of rice under direct underground sowing in flooded paddy field. Lodging degree of broadcast and row sowing at the 15cm tilling depth, were same level, but were higher than in broadcast and row sowing at the 5cm tilling depth. Lodging degree of row sowing at the 5cm tilling depth was lowest, namely, the lodging tolerance was most superior. At the 15cm tilling depth, the pushing resistance and the pulling resistance were higher in row sowing than in broadcast sowing, but the top growth in the row sowing was vigorous, therefore the lodging in the row and broadcast sowing were same level. In the 5cm tillimg depth, it was guessed that the elevation of root activity and strength has brought about the mitigation of lodging, as judged by the numbers of alive leaf sheath, pushing resistance and pulling resistance. But in the 5cm tilling depth, it was considered that the lodging tolerance in broadcast sowing was inferior, by reason that the roots of rice below the hill were scanty

スイトウ ノ タンスイ ドジョウチュウ ジョウハ チョクハ ザイバイ ニ オケル カブ ノ オシタオシ テイコウチ ト ヒキヌキ テイコウチ ト ノ カンケイ

直播水稲の押し倒し抵抗値の測定に用いられている従来型の機種(倒伏試験器)とデジタル式のフォースゲージによる測定値の比較を行うとともに,押し倒し抵抗値と引き抜き抵抗値との関係について検討した。フォースゲージによる押し倒し抵抗の測定値は,従来の倒伏試験器による測定値より大きくなったが,1株穂数が3本以下の押し倒し抵抗値が小さい株の計測も可能であった。一方,押し倒し抵抗値と引き抜き抵抗値との関係は,測定機種や1株穂数の相違に関わらず,両者の間には有意な高い正の相関関係が存在し,しかも引き抜き抵抗値は倒伏指数と有意な負の相関関係が認められた。これらの結果から,フォースゲージは押し倒し抵抗値が小さい株を含む調査対象には,従来の倒伏試験器より高い精度での計測が可能であること,並びに引き抜き抵抗値は根の強度を表す指標の一つとして利用できることが示唆された。This experiment was conducted to compare the pushing resistance of direct-sowing rice, measured by two different methods, namely, prostrate tester (Daiki DIK7400) used at present and digital force gauge (SHIMPO FGX-5). Further, the relationship between the pushing resistance and the pulling resistance were studied. Pushing resistance, measured by two different methods, was higher in value by force gauge than by prostrate tester. Force gauge could measure pushing resistance in rice of low pushing-resistance, where panicle number per hill was less than three. A high positive correlation was found between pushing resistance and pulling resistance without distinction of measures and panicle number per hill. And the pushing resistance showed a high negative correlation with lodging index. From these results, if the pushing resistance of hill is very low, force gauge can measure pushing resistance with greater precision than by measurement with a prostrate tester. Further, it was suggested that the pulling resistance is available to use for one of index of root strength

コウウン シンド ノ ソウイ ガ カンスイ ジカマキ スイトウ ノ コンリョウ ト タイトウフクセイ トノ カンケイ ニ オヨボス エイキョウ

耕耘深度の相違が湛水土壌中直播水稲の耐転び型倒伏性に及ぼす影響を根量との関係を中心にポット栽培で検討した。5cm耕耘区と15cm耕耘区を設け,耕耘深度の設定は土壌充密度の相違,すなわち充密度の低い部分を耕起層とし,その下層部分を高密度状態の不耕起層とした。今回の結果では,倒伏角度は両区に差はなく,TR率が小さいすなわち,地上部生育に比べて地下部生育が良好なものほど耐倒伏性が向上することが認められた。倒伏角度は,耕耘深度が深い15cm区では土壌深層の土壌密度が高い部分の根長と有意な負の相関関係が認められた。しかし,耕耘深度が浅く根量が表層に多く分布した5cm区では,土壌表層の根長と有意な負の相関関係が認められた。以上のように,出穂2週間後の時期では耕耘深度の浅深が実際の倒伏に及ぼす影響はみられなかったが,耕耘深度の相違により耐倒伏性に関与する根長の分布範囲が異なった。A soil-cultured, pot experiment was conducted to investigate the effect of different tilling depth on the lodging tolerance of rice in direct sowing, with special reference to their root weight and length. The field tilling conditions of 5cm or 15cm depth were simulated in pots by the difference of soil filling density for the respective tilling depth, namely, a lower filling density for the tilled surface layer, and a higher one for the non-tilled basal layer. No difference was found in lodging angle between the two conditions. But it was found that the lower top-root ratio of the plants increased the lodging tolerance irrespective of the tilling conditions. In the 15cm tilling depth plot, root length density in the deepest layer was high and there was a close negative correlation with the lodging angle.In the 5cm tilling depth plot, more roots developed in soil surface and the root length density in the surface layer also correlated negatively with the lodging angle. Although the relation between tilling depth and lodging remained obscure two weeks after heading, the distribution of the root length within specific soil layers might have a significant role in the lodging tolerance of the plants

タンスイチョクハンスイトウ ニ オケル コウイブンゲツ ノ ウム ガ ツウジョウブンゲツ ノ シュウリョウカンレンケイシツ ニ オヨボス エイキョウ

湛水直播水稲において,高位分げつが出現した分げつと出現しなかった分げつの収量関連形質を比較した。播種様式を点播とし,苗立ち密度50本/m2(低苗立ち密度)の50本区および100本/m2(適正苗立ち密度)の100本区の2区を設けた。両区とも高位分げつが多く出現し,その出現数は50本区で78.5本/m2および100本区で93.5本/m2であった。両区とも出現した高位分げつの殆どがbT3(止葉節から出現した分げつをbT1とし,求基的に示した分げつ位)とbT4であった。高位分げつが出現した分げつの方が,出現しなかった分げつより1穂籾数,1穂玄米重および登熟歩合が有意に大きかった。高位分げつが出現した分げつの中では,bT4が出現した分げつの方がbT3が出現した分げつより,収量関連形質が大きかった。また,葉数3枚の高位分げつが出現した分げつの方が葉数2枚の高位分げつが出現した分げつより,1穂籾数,1穂玄米重および登熟歩合が大きい傾向が見られた。高位分げつ自身も,bT4の方がbT3より,すべての収量関連形質が大きく,さらに葉数3枚の高位分げつの方が,葉数2枚の高位分げつより登熟歩合を除く収量関連形質が大きい傾向を示した。以上の結果,高位分げつが出現した分げつは,出現しなかった分げつより1穂籾数,1穂玄米重および登熟歩合が大きいことから,出穂期前の蓄積炭水化物が豊富で,しかも出穂期後の炭水化物生産量が多いと推察された。また,高位分げつが出現した分げつの収量関連形質が大きいほど,高位分げつ自身の収量関連形質も大きいことが明らかとなった。Using hill sowing at 50 and 100seedlings/m2, the related yield characteristics of normal tillers (tillers with UNT appearance and tillers without UNT appearance) were compared with the appearance of upper nodal tillers (UNTs) in direct sowing in flooded paddy field rice. UNTs appeared in 50-seedling and 100-seedling plots. The numbers of UNTs per square meter were 78.5 (50-seedling plot) and 93.5 (100-seedling plot). Those with UNT appearance were almost all bT3 and bT4. The number of spikelets per panicle, the weight of brown rice per panicle, and the percentage of ripened grains of tillers with UNT appearance were significantly higher than those of tillers without UNT appearance. Yield characteristics of tillers of bT4 with appearance were higher than those of tillers of bT3 with appearance compared with the tillers with UNT appearance. The number of spikelets per panicle, the weight of brown rice per panicle, and the percentage of ripened grains of tillers of three-leaf UNTs were higher than for tillers of two-leaf UNTs. All related yield characteristics of the bT4 were higher than those of bT3. All related yield characteristics of the three-leaf UNTs were higher than those of the two-leaf UNTs. Therefore, because the number of spikelets per panicle, the weight of brown rice per panicle, and the percentage of ripened grains of the tillers with UNT appearance were higher than those of tillers without UNT appearance, tillers with UNT appearance showed abundant accumulated carbohydrates before the heading stage, and showed high production of carbohydrates after the heading stage. Results clarified that the related yield characteristics of UNTs were high when the related yield characteristics of tillers with UNT appearance were high

スイデンケイハン ニ セイイク スル オオバコ PLANTAGO ASIATICA L. ハ トクチョウテキ ナ シュシハツガトクセイ ヲ ユウスル

水田畦畔において,オオバコは土壌流亡の防止,緑環境の維持の役割を担っている不可欠な植物の一種である。そこでは,畦畔管理としての刈取り作業が実施される。種子でのみ繁殖するオオバコにとって,刈取りは生殖成長・種子繁殖の制限要因となるが,現地では刈取後に幼植物の繁茂が観察される。これには表層土に存在する種子からの発芽・成長が考えられ,水田畦畔では種子の休眠性が弱いことが想定される。そこで,オオバコ種子の発芽特性を,水田畦畔を含む複数の生育地から採取した種子を用いて比較検討した。さらに,水田畦畔および踏み跡広場で生育しているオオバコから採取した成熟種子の季節的出芽特性を比較した。これらの結果をもとに,水田畦畔に生育するオオバコ種子の発芽特性を,刈取りに対する適応性の観点から検討した。その結果,水田畦畔から採取したオオバコ種子はいずれも90%以上の高い発芽率を示した。また,採種時期にかかわらず播種直後に速やかに出芽した。一方,踏み跡広場から採取した種子では,7月中旬に採取した種子は出芽率が低く,秋採取の種子は出芽に遅延がみられ,秋から初冬に採取した種子は播種直後には全く出芽せず,翌春に再出芽あるいは出芽するなど,種子出芽特性にかなり大きな季節変動が示された。以上から,水田畦畔に生育するオオバコの成熟種子は採種場所や採種時期にかかわらず,発芽好適条件下では速やかに発芽できることが判明した。このことから,オオバコは水田畦畔においては,刈取りによって既存植生が一時的に疎となり,地際の光強度が強まる条件で,湿潤な土壌環境を利用して速やかな出芽が可能である特性を有するものと推察される。In paddy field levees, the Asiatic plantain is a necessary plant that supports prevention of soil run-off and maintenance of a green environment. At such places, grass mowing is done as farmland management. For the Asiatic plantain, which reproduces solely from seed, mowing could negatively affect generative growth and seed propagation. Despite this potential damage, thickly regrown seedlings can be observed soon after mowing operations. This rapid emergence response of the plant indicates that many seeds of this species exist in and on the soil. It is assumed that the seed dormancy is weak in the paddy field levee. Thus, the seed dormancy of the Asiatic plantain was investigated using seeds in many growing locations including paddy field levees. Furthermore, seasonal germination characteristics of the Asiatic plantain seed in a paddy field levee were compared with those in other areas (an open land), thereby clarifying the germination characteristics of this plant\u27s seeds. Based on the results obtained, the adaptability for mowing of the Asiatic plantain seed in the paddy field levee was examined.Consequently, the seed collected from the paddy field levee showed a high germination percentage of greater than 90% without exception, and the ratio of dormant seeds was small. Regarding the seeds of plants grown in open land, the emergence varied among seasons : seed collected in mid-July showed a low emergence rate and that in autumn a delayed emergence. The seed collected in the open land during late fall to early winter was unable to emerge soon after sowing, but emerged in the following spring.These results show that, regardless of the seed production season, the mature seeds of the Asiatic plantain growing in paddy field levee can germinate immediately after sowing under environmental conditions suitable for germination. Therefore, it is considered that the seed grown in a certain place begins to germinate in response to full sunlight exposure on the moist soil after mowing, and thereby the Asiatic plantain can succeed its life cycle in the paddy field levee

コウサクチ ニ オケル オオバコ PLANTAGO ASIATICA L. ノ テイチャク ニ オヨボス ヒキヌキ フクド ノ エイキョウ

オオバコは畦畔および農道では旺盛に繁殖するが,耕起地では繁茂しないことが知られている。その要因を解明するため,オオバコおよび比較植物としてメヒシバ,オヒシバおよびスベリヒユを用いて,耕耘を想定した引抜き,埋没処理に対する再生反応,および耕耘後の種子再生産能力推定のための播種期別生殖成長到達日数について検討した。実験1として,3および5葉期の個体を引抜き後,あるいは引抜かずに,それらの個体を深さ2および6cmに土壌で埋没した。対照区には,引抜きおよび埋没をしない区を当てた。その結果,6cmの埋没区においては,引抜きの有無,処理の時期にかかわらず4種とも全く再生しなかったが,2cmの埋没区では,再生程度に著しい種間差があった。オオバコでは無引抜き区において,対照区の3%(3葉期処理)∼17%(5葉期処理),スベリヒユでは引抜き区で3%(3葉期処理)∼27%(5葉期処理),無引抜き区で13%(3葉期処理)∼27%(5葉期処理),メヒシバでは引抜き区および無引抜き区それぞれ3%(3葉期処理)∼7%および20%(5葉期処理),オヒシバでは5葉期の引抜き区のみ3%が再生した。再生個体の草丈は,オオバコにおいて劣った。実験2として,5∼7月に播種したところ,7月播種のオオバコのみ当年内には生殖成長に至らなかった。以上のように,オオバコ個体は耕耘時に土壌から引抜かれ,土壌中に埋没されると全く再生できず,引抜かれなくても土壌埋没によって再生が劣り,草丈も低く,さらに,季節的に遅く出芽した個体では種子生産が当年内に行われず,耕地において生活環の完結が困難になるものと推察された。Asiatic plantain (Plantago asiatica L.) grows thickly and rapidly in levees and farm roads, but not in cultivated fields. We clarified the non-adaptability of Asiatic plantain to fields that had been plowed for management.Generally, plowing pulls up, cuts, and buries plants under the soil. The experiment described herein investigates regrowth responses against artificially simulated “pulling-up” and “soil covering” caused by plowing. Assuming that germination from buried seeds occurs after plowing, florescence occurring within a year from seed sowing was examined. Asiatic plantain was examined along with upland weeds : hairy crabgrass (Digitaria adscendens (H.B.K.) Henr.), goosegrass (Eleusine indica (L.) Gaertn.), and common purslane (Portulaca oleracea L.).Plants in three-leaf and five-leaf stages were pulled up and covered with 2cm or 6cm deep soil. For comparison, plants that had not been pulled up were treated without soil covering (established plants hereinafter).Results show that none of the four plants with soil covering thickness of 6cm regrew. However, with 2-cm-thick coverage, considerable differences were apparent among species. Regarding Asiatic plantain, only 3% (three-leaf stage treatment)-17% (five-leaf stage treatment) of established plants regrew. Regarding common purslane, 3% (three-leaf stage treatment)-27% (five-leaf stage treatment) of the plants regrew when pulled up ; 13% (three-leaf stage treatment)-27% (five-leaf stage treatment) of plants regrew with no pulling-up treatment. For hairy crabgrass, 3% (three-leaf stage treatment)-7% (five-leaf stage treatment) of plants regrew with pulling-up treatment ; 20% of plants regrew in the five-leaf stage with none in the pulling-up treatment. Furthermore, only 3% of the goosegrass pulled up at the five-leaf stage regrew. The regrown Asiatic plantain plant length was considerably less. Of the four species sown in May, June, and July, only the Asiatic plantain did not flower within the year sown in July.As described above, Asiatic plantain, once pulled up from the soil, is unable to regrow. Plants that are covered with soil, even if established, are very small. Seedlings that germinate in the late season (summer) have insufficient time to produce seed. These results underscore that Asiatic plantain cannot complete its life cycle in a frequently plowed field

タイヒ レンネン シヨウ ニ ヨル ザッソウ ハッセイリョウ ノ ヘンカ ト ソノ ヨウイン ノ カイメイ

近年,堆肥を活用した栽培が普及してきたが,それに伴い堆肥施用圃場で発生する雑草の種類およびその量が化学肥料施用圃場とはかなり異なっていることが観察されている。しかし,作物生産圃場でのその詳細な実態についての報告はほとんどない。そこで,本研究では,堆肥施用の有無による雑草発生の差異の実態とその要因について検討した。2002年から2008年までの7年間,両圃場でスイートコーンを栽培し,407年目に調査を行った。本試験での化学肥料施用圃場は化学肥料(N, P^2O^5, K^2O, 各10kg/10a/年)を施用した。堆肥施用圃場は,堆肥(2tDM/10a)および化学肥料(年次によりN, P^2O^5, K^2O各0～2Kg/10a)を施用した。さらに,堆肥施用開始時の変化を明らにするために,堆肥施用履歴のない新規圃場に2007年から同様の試験区(堆肥区の化学肥料はN, P^2O^5, K^2O各2,10,10kg/10a)を設定し,同年と次年度に調査した。結果は以下のとおりである。両試験において,化学肥料施用圃場では,常にメヒシバが優占した。これに対して,堆肥施用圃場では,メヒシバのみでなく,広葉雑草(ホソアオゲイトウ,アメリカタカサブロウなど)が優占する年もあった。スイートコーン栽培期間中と収穫後の雑草の総乾物重は,化学肥料施用圃場に比べ堆肥施用圃場で堆肥施用初年目から明らかに上回る年があった。土壌中の硝酸態窒素濃度は,化学肥料施用圃場に比べ堆肥施用圃場で上回る傾向が見られた。以上のことから,堆肥を施用することによって,優占雑草種に大きな変動が生じるとともに雑草の乾物重が増大する傾向にあることが明らかになった。この変化の要因としては,堆肥の連年施用による土壌中の硝酸態窒素の増加にあると考察された。In recent years, cultivation using compost application has become popular in Japan. The kinds and quantities of weeds in fields with applied compost differ considerably from those in fields using chemical fertilizers. However, few reports describe the effects in crop fields. This study evaluated differences in the appearance of weeds in fields and clarified the factors conducive to them. We cultivated sweet corn in two fields for six years from 2002, and investigated them during years 3-6. To one field, chemical fertilizer was applied (N, P^2O^5, K^2O ; 10kg/10a/yr). To another field, composted animal waste was applied (2 tDM/10a/yr) along with chemical fertilizer (N, P^2O^5, K^2O ; 0-2 kg/10a/yr). Another examination was conducted in 2007 to clarify early changes of compost application in a new field to which compost had not been applied. On field of applied compost in this investigation, a little chemical fertilizer (N, P^2O^5, K^2O ; 2, 10, 10 kg/10a/yr) was used with the compost. The results were the following. In the field using chemical fertilizer alone, Digitaria ciliaris was consistently dominant in both investigations. In contrast, in the field with applied compost, Digitaria ciliaris and several species (Amaranthus patulus, Eclipta alba) of broad-leaf weeds were frequently dominant. The dry matter weight of plants in the field with applied compost surpassed that of the field using chemical fertilizer annually during the sweet corn growing season and after harvesting from the first year of compost application. The nitrate nitrogen concentration of soil in the field with applied compost was higher than that of the field with applied chemical fertilizer. The results described above show that compost application increased the variety of dominant weeds and tended to increase the dry matter weight of weeds. The increase of nitrate nitrogen into the soil caused by continuous application of compost was inferred as a contributing factor to these changes