长期条状施肥下成龄密植库尔勒香梨根系和土壤性状的空间关系

邓永辉1,兖 攀1,安世杰2,陈奇凌2*,郑强卿1,马 凌2,王振东1,王国栋3,刘 静4,王 欣4

1新疆农垦科学院林园研究所,新疆石河子 832000;2新疆农垦科学院铁门关试验站,新疆铁门关 841000;3新疆农垦科学院农田水利与土壤肥料研究所,新疆石河子 832000;4塔里木大学园艺与林学学院,新疆阿拉尔 843300)

摘 要:【目的】 探明长期条状施肥下密植成龄库尔勒香梨根系和土壤理化性质的特征,为密植梨园科学高效水肥管理提供依据。【方法】 采用剖面挖掘法和WinRHIZO 根系分析系统,分析11 年生梨园行间距树干50~200 cm 距离、10~110 cm 深剖面根系的形态和土壤理化性质指标。【结果】 梨根长和根表面积均以吸收根为主,占比分别为92.57%、62.62%;根体积以输导根为主,占比52.98%。在施肥沟附近,根长、根表面积的占比最高,分别为32.32%、27.06%;在深度10~90 cm、水平距离140 cm以内的区域,平均根长密度为0.62 mm·cm-3,占整个采样区域根长的75.56%,表明该区域是梨根系密集分布区。长期条状施肥导致不同养分的富集区存在差异,有机质和速效磷在施肥沟处聚集,表现层性分布的特征,且在深层土壤含量极少,其中10~30 cm 深度土壤有机质、速效磷含量分别是90~110 cm 深层土壤的2.62倍、16.28倍;碱解氮和速效钾由施肥沟向近主干方向分布且其含量显著高于行间方向,50~80 cm处土壤碱解氮、速效钾含量分别是140~170 cm处土壤的1.35倍、1.21倍;碱解氮和速效钾在深层土壤积累,90~110 cm深度碱解氮含量是10~30 cm土层的2.28倍。10~50 cm深度土壤,施肥沟与行间土壤的部分物理性质存在显著差异。与施肥沟处相比,行间距主干150 cm长期受机械碾压处的土壤容重显著增加而孔隙度、饱和持水量、田间持水量均显著下降。吸收根的根长密度与速效磷含量呈极显著正相关。【结论】 长期条状施肥下,有机质和速效养分的空间差异性分布以及施肥沟和机械压实处土壤物理性质的差异是成龄密植库尔勒香梨根系延伸生长的不利因子。

关键词:库尔勒香梨;密植;树龄;根系;土壤养分;空间分布;条状施肥;土壤物理性质

梨是南疆的百亿特色林果产业,2022年新疆梨产量为151.37 万t,全国第二,占全国梨产量的7.86%,主要栽培品种为库尔勒香梨[1]。库尔勒香梨皮薄肉细、香味馥郁、酥脆多汁、贮藏性强,受到国内外消费者的喜爱。库尔勒香梨的区域公用品牌价值从2018 年的98.88 亿元跃升至2023 年的171.28 亿元,在梨中连续6年排名第一[2]。2022年新疆生产建设兵团梨产量为62.41 万t,占新疆梨产量的41.23%,主要分布在南疆第一师、第二师和第三师。其中第二师是新疆香梨的优势产区,近年来该产区主干形密植梨园快速发展,并进入盛果期,面积约0.33 万hm2[3]。密植香梨园株行距一般为1.0 m×4.0 m,株距和冠幅较传统稀植果园窄,有利于机械化管理。但是,随着树龄增长,密植梨园易出现树体抗性弱、易死亡、产量不稳定等问题。施肥方式影响果树根系分布和养分利用,也与树体抗性和产量密切相关[4]。成龄密植梨园施肥多在树冠边缘,即距主干约1 m 处开条状沟施肥,随树龄增长,这种密植条件下的施肥方式是否合理还需要进一步的研究。

掌握根系分布特征是高效水肥管理的基础,对调控树势和产量具有指导意义。关于梨根系多围绕稀植果园开展研究,随树龄增长根系密集区的范围在水平方向不断扩大,如8 年生梨的根系主要分布在水平方向0~1.2 m处[5],而25年生梨的吸收根主要分布在水平方向0~2.5 m[6]。在垂直方向上梨根系密集分布的变化相对较小,不同树龄梨树根系主要集中在0.2~0.9 m 深的土层[7-8],随树龄增长,根系密度的最高区域有下移的趋势。除树龄外,栽植密度也影响果树根系分布,栽植密度不同往往导致施肥管理措施的差异化,如稀植梨园以环状沟或钻施肥穴施肥而密植梨园以条状沟施为主。施肥方式造成养分空间的差异性分布,是决定根系分布特征的重要因素。目前,对密植梨园根系分布特征的研究较为缺乏。已有报道幼龄期密植梨根系主要分布在20~60 cm深的土层[9],6年生密植梨根系密集区水平方向延伸至距主干1.2 m处[10],成龄密植梨园根系的分布特征未见报道。

对梨园土壤理化性质的研究多为大尺度区域性分布调查。研究表明,库尔勒垦区香梨园土壤属性空间异质性强[11],养分具有表聚效应,即随着土壤深度增加,有机质、速效养分含量均逐渐降低[12]。尽管土壤养分具有较强的空间变异性,但长期施肥和种植制度能显著影响土壤养分的空间分布[13-14],并呈现出一定规律性。现有的研究多关注大区域养分分布的差异,忽略了在长期稳定水肥管理方式下单个果园土壤养分空间分布的规律性。与稀植梨园不同,新疆密植梨园施肥、打药均已实现机械化,因受行距和载具的限制,行间距主干150 cm附近的土壤长期被机械碾压,在有限的行间距范围内机械频繁通行造成土壤结构发生显著的变化。机械压实易使土壤容重增加、孔隙度下降,不利于养分流动和根系生长[15]。目前关于密植梨园土壤容重、孔隙度等物理性质的研究较缺乏。

针对长期条状施肥下成龄密植库尔勒香梨根系分布和土壤理化性质特征开展研究,可为密植梨园合理施肥技术创新提供理论支撑,对新疆密植梨园栽培模式的健康持续发展具有重要现实意义。

1 材料和方法

1.1 试验地概况

试验地位于新疆生产建设兵团第二师29 团2连,选择11年生主干形密植库尔勒香梨园,平均产量22 500 kg·hm-2,土壤为砂壤土,砧木为杜梨,东西行向,株行距1.0 m×4.0 m,树干的平均基径为9.50 cm,平均冠幅为2.70 m(南北)×1.60 m(东西)。全年漫灌5次,漫灌时间为3月中旬(萌芽期)、5月(新梢生长期、幼果期)、6月或7月(果实膨大期)、8月(果实成熟期)和10月(果实采收后),灌溉定额为11 250 m3·hm-2。定植第6 年进入结果期后,距离主干约100 cm 处开沟施肥,每年生长季追施复合肥800 kg·hm-2。10月中旬施基肥1 次,隔年施羊粪90 m3·hm-2或生物有机肥1000 kg·hm-2,添加以磷肥为主的复合肥400 kg·hm-2,开沟宽、深均约为20 cm,施羊粪时开沟宽、深均约30 cm。于2023年10月,选取3株平均基径相近、树势健壮的香梨树作为样株,调查根系和土壤理化性质的空间特征。

1.2 测定项目与方法

1.2.1 根系采集与分析 于10月上旬果实采收后,采用剖面挖掘法调查根系的分布特征。参考常规施肥位置,调查区域以树干为中心,在南北两侧距离树干50~200 cm 水平距离处,去除表层10 cm 土壤后,按照分层取样法采集宽30 cm、深110 cm 的区域土壤根系,采样单元大小为30 cm×30 cm×20 cm,具体方法如图1所示。将单个采样单元的带根土样倒入0.1 mm 筛进行浸泡、冲洗,利用Epson V850 Pro扫描仪对根系进行扫描,采用加拿大Regent Instruments 公司生产的WinRHIZO 根系分析软件分析不同径级根系在各采样单元的根长、根表面积、根体积指标。不同深度和水平距离土层根系占比为该土层所有采样单元总根系与整个采样区域根系的比值。参考李宏等[7]、李楠等[8]的方法,按照直径大小将梨根系分为7 个等级,Ⅰ级为0 mm<直径<1 mm,Ⅱ级为1 mm≤直径<2 mm,Ⅲ级为2 mm≤直径<3 mm,Ⅳ级为3 mm≤直径<4 mm,Ⅴ级为4 mm≤直径<5 mm,Ⅵ级为5 mm≤直径<10 mm,Ⅶ级为直径≥10 mm。根据根系功能描述将梨根系分为吸收根(直径<2 mm,对应Ⅰ级和Ⅱ级根系)、输导根(2 mm≤直径<10 mm,对应Ⅲ~Ⅵ级根系)、粗根(直径≥10 mm,对应Ⅶ级根系)[10]

图1 根系采样示意图
Fig.1 Schematic diagram of root sampling

按照以下公式计算单个采样单元(土体体积为18 000 cm3)的根长、根表面积和根体积密度:

1.2.2 土壤样品采集与测定 采用常规分析方法测定土壤养分和物理性质[16]。使用体积为100 cm3的环刀在行间分别距离主干50、100、150、200 cm处取土样,垂直方向每20 cm深度为一层,取样至110 cm深度,测定土壤容重(BD)、孔隙度(TP)、饱和含水量(SMC)和田间持水量(FC)。取根系的同时采集各采样单元的土样,土样风干后用于测定土壤有机质、速效养分含量。利用重铬酸钾容量法-外加热法测定有机质(SOM)含量,利用碱解扩散法测定碱解氮(AN)含量,利用NaHCO3浸提-钼锑抗比色法测定速效磷(AP)含量;利用乙酸铵浸提-火焰光度计测定速效钾(AK)含量。

1.3 数据分析

利用SPSS19 软件进行数据处理与分析,利用Excel 和Origin 作图。相关性分析中不同径级根系的性状指标为根长密度。

2 结果与分析

2.1 梨不同径级根系组成

由图2 可知,成龄库尔勒香梨根长和根表面积均以Ⅰ~Ⅱ级的吸收根为主,占比分别为92.57%、62.62%。整个采样剖面Ⅰ级根系平均根长为13 978.20 cm,占比为77.98%,显著高于其他径级根系;Ⅱ级根系平均根长为2 615.15 cm,占比为14.59%;Ⅲ~Ⅶ级根长占比仅为0.36%~3.36%。Ⅰ级根系根表面积为1 765.10 cm2,占比为38.33%,显著高于其他径级;Ⅱ级根系根表面积为1 118.43 cm2,占比为24.29%;输导根(Ⅲ~Ⅵ级)总表面积占比31.80%,粗根(Ⅶ级)表面积占比仅为5.58%。根体积以输导根为主,输导根根体积为166.55 cm3,占比52.98%,吸收根和粗根的占比分别为20.05%、26.96%。

图2 梨根长、根表面积和根体积的分布和占比
Fig.2 Distribution and proportion of pear root length,root surface area and root volume

2.2 梨根系空间分布特征

由表1可知,垂直方向上,根长、根表面积在30~50 cm 深度土层占比最高,分别为26.30%、25.99%。水平方向上,根系主要分布在距离主干140 cm以内的区域,该区域根长、根表面积、根体积累积占比分别为81.42%、75.95%、71.62%。其中,水平方向距主干80~110 cm 施肥沟处的根长和根表面积占比最高,分别为32.32%、27.06%。

表1 不同深度和水平区域根长、根表面积、根体积占比
Table 1 Proportion of root length,root surface area,and root volume in different vertical and horizontal regions%

指标Index土层深度Soil depth/cm水平距离Horizontal distance/cm根系分布Root distribution 10~30 30~50 50~70 70~90 90~110 50~80 80~110 110~140 140~170 170~200根长占比Root length ratio 19.94±2.53 b 26.30±2.62 a 21.25±4.76 ab 18.43±2.34 b 14.08±1.79 c 25.91±2.50 b 32.32±1.12 a 23.19±1.52 b 7.88±0.84 d 10.70±1.14 c根表面积占比Root surface area ratio 14.03±1.97 b 25.99±3.87 a 19.43±3.57 a 21.02±2.85 a 19.52±2.62 a 25.89±2.63 a 27.06±1.73 a 23.00±1.24 a 10.57±1.53 b 13.49±1.95 b根体积占比Root volumeratio 6.13±1.02 d 21.26±5.50 bc 15.19±3.72 c 33.18±5.20 a 24.25±3.00 b 22.56±5.30 b 18.19±1.54 b 30.87±2.00 a 15.15±1.15 c 13.23±1.46 c

由图3 可知,成龄库尔勒香梨根系主要分布在深度10~90 cm、水平距离50~140 cm的区域,平均根长密度为0.62 mm cm-3,占整个采样区域根长的75.56%。深度10~30 cm的土壤根系分布范围小,水平距离距主干140 cm 以外的区域无根系分布。深度30~110 cm 的土壤根系分布范围大,水平距离均延伸至距主干200 cm处,距主干140 cm以外区域的平均根长密度为0.18 mm cm-3,根系较为稀疏。根表面积和根体积密集区在空间中的分布与根长密集区分布相似,整体上根系呈现倾斜向下分布的特征,随深度增加密集区域向外移动。

图3 根长、根表面积和根体积密度空间分布和各采样单元不同径级根系组成
Fig.3 Spatial distribution of total root length,root surface area,and bulk density,as well as the composition of root systems of different diameter classes in each sampling unit

由图3 采样区域各单元不同径级根系组成可知,吸收根的分布范围最大,随根系粗度增加,分布范围逐渐缩小。Ⅰ~Ⅲ级根系在整个根系分布区均有分布,Ⅶ级粗根分布的区域最小,深度10~30 cm的土层无粗根,深度30~110 cm的土层有粗根,且粗根表现出倾斜向下分布的趋势。在根长密集区吸收根的占比为77.55%~99.67%,所以根长密集区也是吸收根密集分布区。输导根中Ⅲ~Ⅳ级分布范围广,与吸收根分布范围基本一致,Ⅲ~Ⅳ级根系发挥运输养分的关键作用。

2.3 土壤养分空间分布特征

由图4-A可知,水平方向上,有机质和速效磷在距主干80~110 cm处含量最高,其中有机质含量分别是140~170 cm、170~200 cm 处土壤的1.48 倍、2.43倍,速效磷含量分别是2.61倍、4.05倍;垂直方向上,有机质和速效磷在10~50 cm深度土层含量较高,10~30 cm 上层土壤有机质、速效磷含量分别是90~110 cm 深度土壤的2.62 倍、16.28 倍,呈现出养分的表聚效应。碱解氮和速效钾由施肥沟近主干方向分布且其含量显著高于行间方向,水平距离50~110 cm施肥沟近主干处碱解氮、速效钾含量(w,后同)分别为101.88~103.42 mg·kg-1、294.40~297.20 mg·kg-1,显著高于水平距离140~200 cm的行间区域,50~80 cm处土壤碱解氮、速效钾含量分别是140~170 cm 处土壤的1.35倍、1.21倍,是170~200 cm处土壤的1.49倍、1.31 倍。整体上碱解氮含量随土壤深度增加逐渐升高,90~110 cm 深度土层碱解氮含量是10~30 cm土层的2.28倍。速效钾在10~70 cm深度土层含量相近,70~90 cm、90~110 cm 深层土壤速效钾含量较50~70 cm土层分别增加了13.53%、11.54%。

图4 土壤养分在水平和垂直方向的空间分布特征
Fig.4 Spatial distribution characteristics of soil nutrients in horizontal and vertical directions

由图4-B 可知,密植梨园土壤有机质和速效养分富集区的分布不同。有机质和速效磷在条状施肥沟位置处聚集,同时明显表现出层性分布的特征,在深度10~50 cm 土层含量较高。碱解氮和速效钾含量在水平距离50~110 cm区域较高,并在70~110 cm深层土壤积累,表明碱解氮和速效钾在漫灌条件下向下移动性较强。在30~90 cm深度,与施肥沟附近相比,水平方向140~200 cm行间区域碱解氮和速效钾含量下降明显;在90~110 cm 深层土壤不同水平距离土壤碱解氮含量均较高,说明深层土壤碱解氮的横向移动性增强。

2.4 土壤物理性质空间特征

由图5 可知,长期条状施肥下10~50 cm 深度土层,施肥沟和行间土壤部分物理性质存在显著差异,距主干水平距离100 cm施肥沟处土壤容重最小,孔隙度、饱和含水量、田间持水量均显著高于其他水平距离。在10~30 cm深度,距主干150 cm水平距离的行间土壤长期受机械碾压,容重显著高于距主干50、100 cm处,而孔隙度、饱和含水量和田间持水量均显著小于距主干50、100 cm处。50~110 cm深度,不同水平距离的土壤容重无显著差异;距离主干50 cm水平距离的土壤孔隙度、饱和含水量、田间持水量均低于其他水平距离,并在70~110 cm 深度土壤处均显著低于其他水平距离。

图5 土壤物理性质的空间特征
Fig.5 Spatial characteristics of soil physical properties

2.5 根系与土壤性状的相关性分析

由图6 可知,根长密度和土壤养分含量与空间位置关系密切。Ⅴ级、Ⅵ级根系与土壤深度相关系数分别为0.45、0.62,分别呈显著正相关、极显著正相关;Ⅰ级、Ⅳ级根系与水平距离相关系数分别为-0.55、-0.45,呈显著负相关。有机质和速效磷含量与土壤深度的相关系数分别为-0.73、-0.74,均为极显著负相关;碱解氮含量与土壤深度的相关系数为0.55,呈显著正相关;速效钾含量与水平距离相关系数为-0.66,呈极显著负相关。

图6 根系和土壤养分空间分布的相关性分析
Fig.6 Correlation analysis of root distribution and soil nutrient spatial distribution

Ⅰ~Ⅱ级根系与速效磷含量呈极显著正相关,相关系数分别为0.70、0.64。根长密度与土壤容重、孔隙度等物理指标相关性不显著。

3 讨 论

3.1 密植成龄库尔勒香梨根系构成和分布特征

成龄库尔勒香梨根长和根表面积始终以直径小于2 mm的吸收根为主,其中直径小于1 mm的根长占比最高,为77.98%,这与前人研究结果相似[5]。幼龄期香梨根系主要分布在20~60 cm 深度的土层[9]。本研究表明,成龄香梨根系分布的深度和广度增加,与6 年生库尔勒香梨相比[10],10~70 cm 根系密集区根长密度下降,70~110 cm 深层土壤根长密度增长明显,说明成龄香梨树主要通过扩大根系分布范围获取水分和养分,随树龄增长,香梨树对深层土壤水分和养分利用能力增强。

从根系密集区整体分布可见,根系整体呈倾斜向下生长趋势,这种趋势可能受机械压实的影响[15,17]。机械碾压处10~50 cm深度土壤容重显著高于施肥沟处,与水平距离50~140 cm区域相比,距主干140 cm外区域根系密度显著下降,根系表现延伸生长受阻,因此呈现出根系倾斜向下生长的趋势,也表明在行间140~200 cm 范围香梨根系仍有较大的生长空间。与稀植老果园相比[7-8],密植香梨园根系密集区分布范围较窄,根系获取水分养分空间小。同时密植香梨园株距窄、冠幅小,成龄后存在株间遮光的情况[18],单株光合产物的积累量小,树体储存的养分低于稀植梨园。以上原因均可能导致密植香梨树体抗性弱、产量不稳定。

3.2 密植成龄库尔勒香梨园土壤理化性质空间特征

果园土壤养分呈现出表聚效应,有机质和磷在表层土壤的含量显著高于深层土壤[19-20]。本研究表明,有机质和速效磷表现明显的层性分布,在深层土壤含量极少,这与前人研究结果相符[12]。汪宗兰等[11]研究认为库尔勒垦区梨园土壤有机质和速效养分变异与农业生产活动关系密切,采样位置不同导致肥力评价存在差异。研究大尺度的果园土壤肥力时,采样应该考虑常规的水肥管理措施,单个果园土壤养分空间变异性与水肥管理措施密切相关,如滴灌施肥的养分主要聚集在滴头附近,随土层深度加深,养分含量降低[21]。生产中密植主干形香梨园一般在距主干100 cm 行间处开20 cm 深沟施肥,有机质和速效磷移动性弱,在施肥沟位置聚集,这是养分空间变异大的主要原因。笔者发现在70~110 cm深度土壤碱解氮、速效钾含量远高于在10~30 cm深度土壤,说明因长期漫灌碱解氮、速效钾向下运移并在深层土壤积累。研究还发现,碱解氮含量在90~110 cm深度土壤不同水平距离区域均较高。含水量增加显著促进氮素迁移[22],漫灌下90~110 cm 深层土壤保持较高的含水量,促进碱解氮在水平方向移动。

李勇等[23]研究表明,直径1 mm有效根密度和根量的增大,显著增大土壤元素迁移强度,树冠下方靠近主干一侧梨根系密集,更有利于养分在水平方向运移。已有研究表明,土壤容重大、孔隙度小不利于土壤水分入渗,造成持水能力下降[24-25],抑制根系的生长[26-27]。距主干约150 cm行间因打药施肥反复受机械碾压,每年达30次以上,与施肥沟处相比,树冠外行间10~50 cm深度土壤容重增加,不利于养分向行间运移,是水平方向养分分布差异的原因之一。

3.3 密植成龄库尔勒香梨根系分布与土壤性质的关系

根系分布与水平距离和土壤深度有关,同时具有较强的向水向肥性[28-31]。本研究表明,在施肥沟附近根长和根表面积密度占比最高,这与根系化学向性生长特征相符。研究还发现,香梨吸收根根长密度与速效磷含量呈极显著正相关。磷素易被带有正电荷的土壤颗粒结合,移动性弱[30],精准定位施磷位置可显著提高磷的有效性,增加根长和根表面积密度[33-34],磷素空间分布差异性可能是香梨园根系生长分布的限制因子。长期条状施肥下碱解氮、速效磷、速效钾含量和根长密度在水平距离110 cm 以内区域显著高于行间140~200 cm 距离区域,同时,与施肥沟处相比,行间土壤受机械压实影响容重增加、持水能力下降,均不利于根系向行间方向延伸生长。

3.4 密植成龄库尔勒香梨园水肥管理建议

长期条状施肥下,密植梨园有机质和磷素养分在施肥沟及附近聚集,所以施肥位置应适当外扩,如逐年扩大磷肥和有机肥的施肥距离,同时增加施肥深度达40 cm 为宜,以增加养分在深层和水平空间的分布,促进根系扩张和养分吸收。在漫灌条件下,氮素易淋溶至深层土壤,所以氮肥不宜施入过深。在机械碾压位置距主干150 cm附近增施有机肥,通过果园生草、深翻等方式,缓解行间因机械压实导致的土壤孔隙度和持水能力下降等问题,促进养分侧向移动和根系延伸生长。

4 结 论

长期条状施肥下,密植成龄库尔勒香梨吸收根在深度10~90 cm、水平距离140 cm以内的区域密集分布。有机质和速效磷在施肥沟位置聚集,碱解氮、速效磷、速效钾在施肥沟向近主干方向分布且其含量显著高于行间方向。10~50 cm土壤深度,与施肥沟处相比,机械碾压处土壤容重显著增加,孔隙度和田间持水能力均降低。长期条状施肥下养分的空间变异,以及施肥沟和机械压实处土壤物理性质的差异是成龄密植库尔勒香梨根系延伸生长的不利因子。

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Spatial relationship between root system and soil properties of mature and densely planted Kuerlexiangli pear under long-term strip fertilization

DENG Yonghui1,YAN Pan1,AN Shijie2,CHEN Qiling2*,ZHENG Qiangqing1,MA Ling2,WANG Zhendong1,WANG Guodong3,LIU Jing4,WANG Xin4
(1Institute of Forestry and Horticulture, Xinjiang Academy of Agricultural and Reclamation Science, Shihezi 832000, Xinjiang, China;2Tiemenguan Experimental Station,Xinjiang Academy of Agricultural and Reclamation Science,Tiemenguan 841000,Xinjiang,China;3Institute of Agricultural Hydrology and Soil Fertiliser, Xinjiang Academy of Agricultural and Reclamation Science, Shihezi 832000,Xinjiang,China;4Horticulture and Forestry College,Tarim University,Alar 843300,Xinjiang,China)

Abstract:【Objective】Kuerlexiangli pear(Pyrus sinkiangensis Yü et Lu.)is the main cultivar in Southern Xinjiang.In recent years,the main trunk dense planting pear orchard has developed rapidly and entered the peak fruiting period.With the increase of tree age,problems such as poor resistance,death vulnerability,and unstable yield have become prominent in dense planting pear orchard.Fertilization methods affect the distribution of the roots of the fruit tree and nutrient utilization,and are closely related to tree resistance and yield.Fertilization in mature and densely planted pear orchards is often carried out at the edge of the tree crown,about 1 meter away from the main trunk,by opening a strip-shaped ditch for fertilization.As the tree ages, further research is needed to determine whether this fertilization method is reasonable under dense planting conditions. The study aimed to survey the spatial characteristics of the root system and soil physicochemical properties of the densely planted mature Korla pears under long-term strip fertilization in order to provide a basis for scientific and efficient water and fertilizer management in the densely planted pear orchards.【Methods】Using the profile excavation method and WinRHIZO root analysis system,the root morphology of 11 year old Kuerlexiangli pear with Pyrus betulifolia Bunge as rootstock was analyzed at a distance of 50-200 cm between the rows and tree trunks,and at a depth of 10-110 cm.The soil organic matter,available nutrients,soil bulk density,porosity,saturated water content, field water holding capacity and other soil physical and chemical properties were measured.【Results】The results showed that the length and surface area of the pear roots were mainly dominated by the absorbing roots, accounting for 92.57% and 62.62%, respectively; The root volume was mainly composed of the conducting roots, accounting for 52.98%. In the horizontal direction, the root length and root surface area density were the highest near the fertilization ditch, accounting for 32.32%and 27.06%respectively;The proportion of the root length and root surface area in the soil layer at a depth of 30-50 cm in the vertical direction was the highest,accounting for 26.30%and 25.99%,respectively.The average root length density in the area with a depth of 10-90 cm and a horizontal distance of 140 cm was 0.62 mm·cm-3,accounting for 75.56%of the total root length in the sampling area.It was the densely distributed area of pear root system. There were differences in the enrichment areas of the different nutrients in long-term strip fertilization orchard.The organic matter and available phosphorus accumulated at a distance of 1 meter from the main stem in the fertilization ditch, and exhibit layered distribution characteristics.The content of the organic matter and available phosphorus contents at a depth of 10-30 cm were 2.62 times and 16.28 times higher than those at a depth of 90-110 cm,respectively. The content of the alkaline nitrogen and available potassium in the soil at 50-80 cm were 1.35 times and 1.21 times higher than those at 140-170 cm,respectively;The alkaline hydrolyzable nitrogen content at depths of 90-110 cm was 2.28 times higher than that at depths of 10-30 cm. There was a significant difference in the physical properties of the soil between the fertilization ditches and rows at a depth of 10-50 cm.Compared with the fertilization ditches,the soil bulk density significantly increased while the porosity, saturated water holding capacity, and field water holding capacity decreased in the distance of 150 cm away from the main stem due to the mechanical compaction for a long time.The nutrient content of the roots and soil was closely related to spatial location.The correlation coefficients between the V and Ⅵgrade roots and soil depth were 0.45 and 0.62, respectively.The correlation coefficients between the Ⅰand Ⅳgrade roots and horizontal distance were-0.55 and-0.45,respectively;The correlation coefficients between the organic matter and available phosphorus and soil depth were-0.73 and-0.74, respectively.The correlation coefficient between the alkaline nitrogen and soil depth is 0.55. The correlation coefficient between the available potassium content and horizontal distance was-0.66. There was a highly significant and positive correlation between the grade Ⅰ-Ⅱroot systems and available phosphorus (r= 0.70 and 0.64, respectively).【Conclusion】In summary, under long-term strip fertilization,the organic matter and phosphorus nutrients in the densely planted Kuerlexiangli pear orchard accumulated in and near the fertilization ditch, and the soil porosity and water holding capacity in the soil between the rows decreased. The spatial differences in the distribution of the organic matter and available nutrients, as well as the differences in the soil physical properties between the fertilization ditch and mechanical compaction site would be unfavorable factors for the root extension and growth of mature densely planted Kuerlexiangli pear orchards.

Key words:Kuerlexiangli pear; Close planting;Tree age; Root system; Soil nutrients; Spatial distribution;Strip fertilization;Soil physical properties

中图分类号:S661.2

文献标志码:A

文章编号:1009-9980(2025)02-0336-12

DOI:10.13925/j.cnki.gsxb.20240551

收稿日期:2024-10-23

接受日期:2024-12-02

基金项目:兵团农业科技创新工程专项(NCG202312);新疆农垦科学院院级项目(2023YJ008)

作者简介:邓永辉,男,助理研究员,硕士,研究方向为果树栽培生理生态。E-mail:923236203@qq.com

*通信作者 Author for correspondence.E-mail:Cql619@163.com