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

Abstract

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