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No.40 (1993/12) >

Title :琉球列島のサトウキビ畑における雑草の生理・生態 : 第 13 報 ハイキビ (Panicum repens L.) の除草時期がサトウキビの初期生育に及ぼす影響(附属農場)
Title alternative :Physiological and Ecological Characteristics of Sugarcane Field Weeds in the Ryukyu Islands : 13. Effect of Weeding time of Torpedo grass (Panicum repens L.) on Early Stage of Sugarcane Growth (Agricultural Experiment Station)
Authors :石嶺, 行男
ホサイン, M. A.
本村, 恵二
赤嶺, 光
村山, 盛一
古謝, 瑞幸
Authors alternative :Ishimine, Yukio
Hossain, M. A.
Motomura, Keiji
Akamine, Hikaru
Murayama, Seiichi
Koja, Zuiko
Issue Date :1-Dec-1993
Abstract :熱帯・亜熱帯地域の畑地にみられるイネ科多年生雑草ハイキビは,地下茎によって旺盛に繁殖し,畑地に群落を形成することから,農作物へ与える影響が大きい。本報では,ハイキビの除草時期がサトウキビの初期生育に及ぼす影響について調べ,サトウキビ畑におけるハイキビの合理的な除草時期を検討した。実験は,1/2000aワグネルポットの中央にいずれも一節苗に揃えたサトウキビ(品種 : F-160)を植え,その回りに二節苗に調整したハイキビの地下茎をそれぞれ2本植え,4本植え,8本植えし,さらに,それぞれを植付日から30日目除草区(30DAP),60日目除草区(60DAP),120日目除草区(120DAP)及び無除草区に分け実施した。対照区としてはサトウキビ,ハイキビそれぞれの単植区を設けた。調査は,植付日から30日毎に210日目までサトウキビの草丈,茎長,茎径,分げつ数,ハイキビの草丈,分げつ数を計7回測定した。また,最終調査日の210日目には堀り取り調査を行い,サトウキビの茎重,根重,葉面積,ハイキビの地上部重,根重を測定し,さらに除草区の中で,混植していた間に形成されたハイキビの地下茎残存の有無を調べた。その結果,草丈の生長速度の急速な増加はサトウキビでは植付後60∿90日の間に見られ(Fig.1),ハイキビでは120日までの間に高い値を示した(Fig.2)。また両者とも150日まで草丈の伸長が高く,その後はゆるやかな伸長を示した。これらのことから,両者間の養分競合が植付後150日までの期間に起こることが考えられる。また,サトウキビの分げつは,いずれの区においても除草前には見られなかったが,除草後に見られた(Fig.3)。したがってハイキビがサトウキビの分げつを抑制していることが推察された。さらに,最終調査の結果,除草時期が遅延するにしたがって,サトウキビの茎長,茎径,茎重,根重は著しく減少した(Table 4)。また,無除草区の収量(茎重)はサトウキビ単植区に比べ70%減少という大きな数値を示した(Fig.4)。一方,除草後にハイキビの地下茎が残存しているポットの割合は,30DAPでは0%,60DAPでは13%,120DAPでは100%であったことから,ハイキビの地下茎は植付日から30日以降に形成されると考えられる。これらの実験の結果により,サトウキビの生育への影響および除草効果を考慮してハイキビの除草時期を検討すると,サトウキビの収量形質の減少が30日から次第に増え60日以降大きくなることから,ハイキビ2本植え,4本植え,8本植えのいずれの区においても,植付後30から60日以内の除草が適切と思われる。
A glass house pot experiment consisted of six treatments. For treatment A, only one cane sett was planted in each pot. For treatment B, one pot was planted one cane sett and two weed cuttings, one pot was planted one cane sett and four weed cuttings, and one pot was planted one cane sett and eight weed cuttings with five replications. Same procedure was done for the treatments C, D and E. For the treatment F, only one weed cutting was planted in each pot. The experiment was carried out from 18th May to 23rd December. 1992,at the experimental farm, College of Agriculture, University of the Ryukyus to study the effect of weeding time of Torpedo grass on early stage of sugarcane growth to determine the proper weeding time of this weed infested sugarcane field. Dark redish soil of pH 5.25-6.74,two-noded sprouted rhizome of Torpedo grass, one-eyed sugarcane sett (F-160), compound fertilizer (N : P : K=2.6 : 2.0 : 2.8), wagner pot (1/2000a), organic phosphorus pesticide were used in the experiment. The results were summarized as follows : 1. Early stage of sugarcane was up to 150 days after planting (DAP) and its elongation rate was increased fastly from 60-90 DAP. On the other hand, Torpedo grass was increased up to 150 DAP, but increasing was occured very sharply up to 120 DAP, it's tiller increasing rate was highest from 30-60 DAP. So high competition was occured up to 150 DAP between sugarcane and Torpedo grass in absorption of plant nutrient. 2. Before weeding, cane growth was almost stunted and no tiller was come out for the loose mat forming rhizome of the said weed. Early weeding always gave higher plant length and early tillers as the period of weeding was prolonged that is reflected more survaival of tillers and cane formation, ultimately resulted in higher cane yield/unit area. 3. Stalk lenght, stalk diameter, stalk fresh (yield) weight, dry weight of stalk, dry weight of green leaf and dry weight of root were highest in the weed free cane and lowest in the unweeded cane. Weeding showed good effect on the yield parameters of cane. Early weeding increased yield cotributing parameters as the weeding was prolonged that ultimate resulted in higher cane yield/unit area. Torpedo grass decreased 65-80% sugarcane yield compared to pure cane. On the other hand, weeding increased 19-134% yield compared to non-weeded cane, early weeding (30-60 DAP) gave 45-97% higher yield compared to late weeded cane. 4. The visual observation showed no rhizome in the mixed pots which were weeded at 30 DAP, but at 60 DAP weeded pots showed 13% and 120 DAP weeded pots showed 100% of rhizome at final harvest. Therefore, the results demonstrated that growth of sugarcane can be recovered to satisfactory level either by removing weeds from the sugarcane field or by suppressing the weed growth below economic injury level. For successful weed control and getting higher yield in Torpedo grass infested field, sugarcane field must kept free from this weed up to 150 DAP and first removal of weeds may be recomended within 30-60 days after planting in all density of weed infested field such as cane+two weeds, cane+four weeds and cane+eight weeds.
Type Local :紀要論文
ISSN :0370-4246
Publisher :琉球大学農学部
URI :http://hdl.handle.net/20.500.12000/3800
Citation :琉球大学農学部学術報告 = The Science Bulletin of the Faculty of Agriculture. University of the Ryukyus no.40 p.143 -152
Appears in Collections:No.40 (1993/12)

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