Abstract：Objective]Thisresearchaimedtoinvestigatetheoptimalrowspacingandplantingdensityofmechancallharvested cottonintheYangtzeRiverBasin.[Methods]FieldtrialswereconductedinChangsha，Yueyang，andHengyangCitiesinHunan Province in 2024，using the JXoo10 cotton varietyas the experimental material.The main plot included thre row spacing treatments： 90cm （L1）， 83cm （L2）， and 76cm （L3），while the subplot had three planting density treatments： 60 ooo plants （D1），75 000 plants （D2），and 90 000 plants ⋅hm^-2 （D3）.The plant architecture，aboveground dry matter mass，net photosynthetic rate （P_n） ，chlorophyll content （soil and plant analyzer development，SPAD value），leaf area index （LAI），and yield traits werecomparedunderdierenttreatments.Results]At thesamerowspacing，asplantingdensityicreased，plantheight tendedtoincrease，whilethenumberoffruitingbranches，stemdiameter，andlengthofthefourthfruitingbranchtendedto decrease.Theheightofthefirstfruiting branch was higherunderL1D3treatment.Atthefullsquaring stage，theaboveground drymatermassperplanttended toincreasewiththeincreasingofplanting densityat thesamerowspacing.Tedrymattermass of stems，leaves，reproductiveorgans，andwholeplant were higherunderL1D3treatmentatthefullsquaring stage，full floweringstage，fullboll-setingstage，andbollopeningstage.Atthefullfloweringstageandfullboll-setingstage， P_n was higher under the D2 treatment at the same row spacing;at the boll opening stage， P_n tended to increase with the increasing of planting density，and P_n was higher under L1D3 treatment.At the same row spacing，SPAD value and LAI （except for the L1 treatmentin Changshaatthefullsquaring stage）increased withthe increasingofplantingdensityfromthefullsquaringstage to bollopeningstage.TheL1D3treatment hadthe highestnumberofbolsperplant.Underthesamerowspacing，sedcoton yieldandlintyieldincreasedwiththeincreasingofplantingdnsity，withLD3treatmentshowingthehighestseedottonyield andlintyield，whichweresignificantlyhigherthantheotherseven treatments （expceptL2D3 treatment）atbothYueyangand Hengyang test sites.[Conclusion] Under the conditions of this experiment， the optimal row spacing for JX0010 cotton is 90cm 0 and the optimal planting density is 90 ooo plants·hm^-2

Keywords：coton;rowspacing;density;yield;plantarchitecture;photosyntheticperformance;coton-growingregionof the Yangtze River Basin

棉花是纺织纤维的重要来源，在国民经济发展中有重要作用。长江流域棉区是我国棉花主产区之一。目前，长江流域棉区棉花基本依靠人工采收，机械化程度低，劳动强度大，植棉成本较高，已严重制约当地棉花产业的发展[1。机械化采收是解决棉花种植过程中消耗大量劳动力的重要手段。

机采棉是我国棉花产业发展的方向，株型结构是机械化采收能否成功的重要指标。棉花的株型和产量不仅受遗传因素的影响[，还与田间管理措施密切相关，而种植密度与行距配置是塑造棉花株型的重要方法，也是实现棉花机械化采收的重要手段。通过合理调整棉花种植密度和行距，可优化群体结构，提高棉花产量和纤维品质]。研究表明，在新疆早熟植棉区，相同行距下，随种植密度（12万、15万、18万株 hm^-2 ）增大，棉花株高增加、茎粗降低、单株结铃数减少；不同行距下的棉花产量均随种植密度的增大而提高[4]。李建峰等[研究表明，等行距低密度种植有利于棉花生育后期棉田通风透光，优化棉花冠层结构，增强群体的光合作用，增加结铃数和铃重，显著提高机采棉产量。种植密度和行距配置会影响光能利用率，最终影响作物产量。研究表明，低密度（1.5万株 ⋅hm^-2 ）下的棉花植株较高，而高密度（10.5万株 ⋅hm^-2 ）下的棉花单位面积铃数较多，籽棉产量和皮棉产量也高于低密度。高密度的等行距种植模式下棉花可以获得更多的光截获和更高的光能利用率[910]。

目前，关于种植密度或行距对棉花产量影响的研究报道较多，但在长江流域特殊的气候条件下，关于不同密度和株行距配置对机采棉株型和产量影响的研究报道较少，且长江流域机采棉的适宜种植模式尚不明确。……