タナザワスイデン ニ オケル スイトウ ノ サイテキエイカスウ ト タイナイチッソリョウ ノ ケントウ

本研究は都市型農業がおこなわれている神奈川県厚木市の棚沢地区において,高度効率化を目指した窒素施肥管理の確立のために行ったもので,ここでは水稲の収量を最大にする最適穎花数とそのために必要な体内窒素量を検討した。栽培試験は東京農業大学棚沢水田において1998年から2008年にかけて行った。供試品種は水稲日本晴,コシヒカリおよびタカナリとし,試験区は典型的に施肥法が異なるもの,および基肥施用の有無と異なる追肥時期の組み合わせたもので構成し,合計180区であった。調査項目は収量および収量構成要,体内窒素濃度および体内窒素量の経時変化であった。タカナリは日本晴やコシヒカリよりも一穂穎花数が多い傾向にあり,その結果,単位面積あたり穎花数および玄米収量が明らかに多かった。単位面積あたり穎花数と玄米収量の関係は日本晴およびコシヒカリの日本型品種とタカナリとは明らかに異なった。収量を最大にする最適穎花数は日本晴およびコシヒカリでは35,000,タカナリでは48,000m-2であった。また,単位面積あたり穎花数は穎化分化終期および出穂期における体内窒素量の間には品種ごとに密接な関係があった。それらの関係を用いて最適穎花数に到達するために必要な出穂期における体内窒素量は日本晴,コシヒカリ,タカナリのそれぞれ,12.5,16.0,17.2gm-2であった。一方,無窒素区から算出した天然供給由来の吸収窒素量は体内窒素量の50～60%であり,残りは施肥に依存することになる。したがって,棚沢水田における水稲栽培では,最適穎花数を確保するために吸収率が高い幼穂発育期を中心とした窒素追肥を積極的に行うことが推奨される。The objective of this study is to clarify regional optimum spikelet number for maximum grain yield for each cultivar, and plant N for spikelet number to obtain stable yield in rice. We conducted field experiments in a paddy field at Tanazawa District as city agriculture in order to establish highly effective N application management regionally. We analyzed 180 sets of experimental data on yield and its component, and plant N at the late spikelet differentiation and heading stage, using three low land cultivars, Nipponbare, Koshihikari and Takanari, grown under different methods and levels of N application over 9 seasons from 1998 to 2008. We made use of variously different split application of N, including basal application only (B), light basal and heavy top-dressings from the panicle initiation stage onward (L), heavy basal and heavy top-dressings from the spikelet formation stage onward (V), and no applications (0) in 1998-2001. In 2002, and 2005-2008 we set up experimental plots of the timing of a N top-dressing both with and without basal application of N. We investigated yield and its components and plant N at the late spikelet differentiation stage and heading.Takanari tended to have the largest spikelet number and grain yield averaged over all plots. Optimum spikelet number for maximum grain yield was about 35000m-2 in Nipponbare and Koshihikari, and about 48000m-2 in Takanari, respectively. The relationship between spikelet number per unit area and plant N at the late spikelet differentiation stage or heading stage was close. Plant N for optimum spikelet number determined by those relationships was 12.8, 11.4 and 12.3g m-2 at the late differentiation stage, and 12.5, 16.0 and 17.2g m-2 at heading, in Nipponabare, Koshihikari and Takanari, respectively. A grain yield of 600g m-2 in Nipponbare and Koshihikari and 750g m-2 in Takanari would require spikelet numbers per unit area of 32000, 32000 and 40000, respectively, assuming that the percentage of ripened spikelets is 85%. To obtain these spikelet numbers, plant N must reach 12.1, 11.0 and 9.1g m-2 at the heading stage for these cultivars, respectively.Plant N derived from natural supply of N was 50-60% of total plant N at the late spikelet differentiation stage or heading stage. Therefore, to optimize spikelet number, we should make use of application of N top-dressing for the early panicle development stage, since rice can absorb much nitrogen, especially the cultivar Takanari

コトナル ニッシャカンキョウ ト ポットドジョウヨウセキ ガ スイトウ ノ セイイク ニ オヨボス エイキョウ

制限された日射環境の屋上緑化スペースにポットイネを導入するのに必要な基礎資料を得るため,東京農業大学世田谷キャンパス構内の建物屋上と作物実験用網室において,日本晴,中生新千本およびタカナリの水稲3品種をそれぞれ 1/2000 a と 1/5000 a のワグネルポットで栽培し,それらの生育と関連気象条件を調べた栽培期間中の気温や飽差には場所による差がなかったが網室における実験期間中の平均日射透過率は約60%であった地上部および地下部乾物重は 1/2000 a ポットに対し,1/5000 a ポットでは50～70%および30～50%の範囲にあり,土壌容積が乾物生産に及ぼす影響は大きかった。屋上における 1/2000 a ポットの株あたり穂数は日本晴が19本,中生新千本が18本,タカナリが16本程度であったのに対し,網室ではいずれも約13本と少なかった。また網室,屋上ともに1/5000 a ポットの3品種の穂数はいずれも6本程度で,1/2000 a ポットの1/2～1/3であった。1穂穎花数は明らかに屋上<網室であったが,網室では穂数がやや少なく,株あたり総穎花数は,1/2000 a ポットでは屋上において日本晴と中生新千本がおよそ1300,タカナリがおよそ2100,網室においてそれぞれおよそ1200,1800となり,屋上がやや多い傾向があった。これに対し,1/5000 a ポットでは,穂数,一穂穎花数ともに場所による差は小さく,株あたり総穎花数は屋上で3品種ともおよそ400,網室で日本晴と中生新千本がおよそ300,タカナリでおよそ500であった。穂重型品種のタカナリはポットにおいて一穂穎花数が多いという特性が表われなかった屋上緑化スペースにポットイネを導入する際には軽量化を考慮すると土壌容積を小さくすることが望ましいが,本実験の日射環境下ではイネの生育に対し土壌容積の制約が大きいことが示された。To obtain basic information on introducing potted rice plants to semi-shaded places in building complexes, the growth and development were investigated under semi-shaded conditions in an experimental net house and at a sunny site on a at rooftop at the Setagaya Campus of Tokyo University of Agriculture in 2008. The paddy rice cultivars Nipponbare, Nakateshinsenbon, and Takanari were planted in 1/5000 a and 1/2000 a Wagner pots. The daily solar radiation in the net house was approximately 60% of that on the rooftop. There were no large differences in air temperature and vapor pressure deficit between the net house and rooftop. The top dry matter of the rice in the 1/5000 a pots was 40%～60% of that in the 1/2000 a pots and the root matter was 30～50%, indicating that the soil volume in the root zone had a large effect on the dry matter production of the rice. There were about 13 panicles per hill in the 1/2000 a pots for all cultivars in the net house, versus 19, 18, and 16, respectively, for the Nipponbare, Nakateshinsenbon, and Takanari cultivars on the rooftop. In the 1/5000 a pots, there were about 6.0 panicles per hill, roughly 1/2 to 1/3 of the number in the 1/2000 a pots for all cultivars on both the rooftop and in the net house. In the 1/2000 a pots, there were 1300, 1300, and 2100 spikelets per hill for Nipponbare, Nakateshinsenbon, and Takanari, respectively, on the rooftop, versus 1200, 1200, and 1900 in the net house. In contrast, in the 1/5000 a pots, there were 400~500 spikelets for all three cultivars, and the dierence between the two sites was small. Although we have to design the soil volume to be small because of the weigh, our results suggest that a smaller volume of soil in the root zone limits the growth and development of rice in semi-shaded conditions

スイトウシュカンバスウ ノ ヒョウジュンガタ オヨビ ゲンヨウガタ ニ オケル ケイタイテキトクセイ

本研究は1/5000aワグネルポットに円形20株密植栽培した日本晴,コシヒカリおよびタカナリの水稲3品種について,総葉数の異なる主稈の出穂日,穂長,葉身長,葉鞘長および節間長を比較検討したもので,2009年に東京農業大学世田谷キャンパス網室で行った。3品種ともに主稈葉数に1枚の差が生じる標準型と減葉型の異なる生育型が発現した。標準型および減葉型の出現比率は試験区により変動し,コシヒカリおよび日本晴では標準型の集中する傾向にあったが,タカナリは2つの生育型に分かれる傾向にあった。タカナリではこの2つの生育型の形質間には有意な差がみられ,減葉型は標準型に比べ,出穂日はほとんど変わらなかったが,上位葉身が長く,下位節間が短い傾向を示した。また,窒素追肥および稈基部遮光が器官伸長に及ぼす影響を3品種の標準型および減葉型について検討したところ,幼穂発育期前半の窒素追肥は上位葉身長や上位節間長を高める傾向にあり,幼穂発育期間を通じた窒素追肥や稈基部遮光処理は下位節間を伸長させた。これらの影響は品種間および生育型間では大きな差が認められなかったことから,下位節間に着目した水稲の形態的制御を行う場合には,生育型を厳密に分ける必要性がないことが示唆された。We conducted pot experiments using three rice cultivars, Nipponbare, Koshihikari and Takanari in the net house at Setagaya Campus of Tokyo University of Agriculture in 2009. Twenty plants per pot were circular-dense-transplanted, and harvested at maturity to investigate the total leaf number on the main culms, and the lengths of panicle, leaf blades, leaf sheaths and internodes. We also researched the heading time, and the effects of nitrogen top-dressing and shading in the base of culms during the panicle development stage on the lengths of organs. Two types of the total leaf number on the main culms were confirmed. One was the standard type, and the other was the less-leaf type. Most of the culms were standard type in Nipponbare, and Koshihikari, but the culms of Takanari was divided into two types. There were clear differences in characteristics between the standard type and the less-leaf type, especially in Takanari. Less-leaf type culms tended to be longer in upper leaves and shorter in lower internodes than standard type culms. However, the effects of nitrogen top-dressing and shading on lengths of organs were likely to be roughly constant through cultivars or leaf number types. These results suggest that we need not control internode elongation with the consideration of leaf number types

スイトウシュカンバスウ ノ ヒョウジュンガタ オヨビ ゲンヨウガタ ニ オケル ケイタイテキトクセイ

本研究は1/5000aワグネルポットに円形20株密植栽培した日本晴,コシヒカリおよびタカナリの水稲3品種について,総葉数の異なる主稈の出穂日,穂長,葉身長,葉鞘長および節間長を比較検討したもので,2009年に東京農業大学世田谷キャンパス網室で行った。3品種ともに主稈葉数に1枚の差が生じる標準型と減葉型の異なる生育型が発現した。標準型および減葉型の出現比率は試験区により変動し,コシヒカリおよび日本晴では標準型の集中する傾向にあったが,タカナリは2つの生育型に分かれる傾向にあった。タカナリではこの2つの生育型の形質間には有意な差がみられ,減葉型は標準型に比べ,出穂日はほとんど変わらなかったが,上位葉身が長く,下位節間が短い傾向を示した。また,窒素追肥および稈基部遮光が器官伸長に及ぼす影響を3品種の標準型および減葉型について検討したところ,幼穂発育期前半の窒素追肥は上位葉身長や上位節間長を高める傾向にあり,幼穂発育期間を通じた窒素追肥や稈基部遮光処理は下位節間を伸長させた。これらの影響は品種間および生育型間では大きな差が認められなかったことから,下位節間に着目した水稲の形態的制御を行う場合には,生育型を厳密に分ける必要性がないことが示唆された。We conducted pot experiments using three rice cultivars, Nipponbare, Koshihikari and Takanari in the net house at Setagaya Campus of Tokyo University of Agriculture in 2009. Twenty plants per pot were circular-dense-transplanted, and harvested at maturity to investigate the total leaf number on the main culms, and the lengths of panicle, leaf blades, leaf sheaths and internodes. We also researched the heading time, and the effects of nitrogen top-dressing and shading in the base of culms during the panicle development stage on the lengths of organs. Two types of the total leaf number on the main culms were confirmed. One was the standard type, and the other was the less-leaf type. Most of the culms were standard type in Nipponbare, and Koshihikari, but the culms of Takanari was divided into two types. There were clear differences in characteristics between the standard type and the less-leaf type, especially in Takanari. Less-leaf type culms tended to be longer in upper leaves and shorter in lower internodes than standard type culms. However, the effects of nitrogen top-dressing and shading on lengths of organs were likely to be roughly constant through cultivars or leaf number types. These results suggest that we need not control internode elongation with the consideration of leaf number types

Effects of Waterlogging at Vegetative and Reproductive Growth Stages on Photosynthesis, Leaf Water Potential and Yield in Mungbean

The effects of short-term waterlogging on mungbean and recovery from the damage were studied in a plastic greenhouse. Pot-grown plants of two mungbean cultivars, KPS1 and CNXP-49 were waterlogged for eight days, at the vegetative and reproductive growth stages. Photosynthetic rate (P), transpiration rate (Tr), diffusive resistance (rs) and leaf water potential (Ψl) were measured at the 1st, 4th and 8th day of the 8-day waterlogging treatment and at the 4th and 8th day after the end of waterlogging. P was reduced significantly by waterlogging. It was reduced by 58 and 64% at the 8th day of waterlogging at the vegetative and reproductive stages, respectively, in KPS1 and, by 76 and 82%, respectively, in CNXP-49. Tr was reduced by 48 and 66% in KPS1 and CNXP-49 respectively, at the 8th day of waterlogging at both stages. The diffusive resistance at the 8th day of waterlogging was increased by 79 and 83%, in KPS1 and CNXP-49, respectively, at the vegetative stage, and by 76 and 79% at the reproductive stage. All these physiological parameters of both cultivars recovered to almost normal values within 4 days after the end of waterlogging at the reproductive stage and within 8 days at the vegetative stage. Waterlogging did not affect Ψl, indicating that the decrease in P and Tr was not associated with leaf dehydration. Waterlogging at the vegetative and reproductive stages significantly reduced the dry matter accumulation during and after the waterlogging in both KPS1 and CNXP-49. Final seed yield in KPS1 and CNXP-49 was reduced by 16 and 19%, respectively, by the waterlogging at the vegetative stage and by 23 and 30%, respectively, by that at the reproductive stage. Although even short-term waterlogging markedly affected P, Tr and rs of mungbean, the damage particularly in P and leaf growth was quickly recovered after the end of waterlogging and the reduction of seed yield was less than that expected from the damage in the physiological characteristics. These results, suggest that mungbean has an ability to recover from the short-term waterlogging damage and that the response to waterlogging varies with the cultivar