植物生态学报

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黄土高原长期覆膜苹果园土壤物理退化与细根生长响应研究

孙文泰,马明   

  1. 甘肃省农业科学院林果花卉研究所
  • 收稿日期:2021-07-02 修回日期:2021-07-17 出版日期:2021-08-26 发布日期:2021-08-26
  • 通讯作者: 孙文泰
  • 基金资助:
    西北黄土高原雨养农业区长期覆膜苹果树根系生长障碍的进程与机理;苹果化肥农药减施增效技术集成研究与示范;农业农村部西北地区果树科学观测实验站

Response of soil physical degradation and fine root growth on long-term film mulching in apple orchards on Loess Plateau

,ma ming   

  1. Insititute of Fruit and Floricultures Research,Gansu Academy of Agricultural Sciences
  • Received:2021-07-02 Revised:2021-07-17 Online:2021-08-26 Published:2021-08-26

摘要: 甘肃陇东黄土高原为我国苹果主产区之一, 生产中多采取覆膜方式节水保墒, 但长期覆膜易导致土壤理化性状退化及苹果根系生长障碍。为探明长期覆膜对苹果园表层土壤(0–20 cm)、亚表层土壤(20–40 cm)理化特性、土壤结构稳定性及苹果细根数量、形态、构型、解剖性状的影响,以18年生苹果树为试验材料, 于苹果树发根高峰(果实采后至落叶期), 以清耕(CK)为对照,采用土壤剖面法系统调查覆膜2年(2Y)、覆膜4年(4Y)、覆膜6年(6Y) 的表层土壤、亚表层土壤物理性状变化趋势,苹果根系根长、表面积、比根长、导管直径、导管密度等指标的空间分布特征。并借助主成分分析, 抽取覆膜条件下根系与土壤主要因子, 分析应对根际土壤物理退化的苹果树细根生长适应策略调整。结果表明: 短期覆膜(2Y)可有效改善亚表层土壤含水量、总孔隙度, 分别比清耕(CK)提高了18.04%、4.53%,土壤容重降低了2.36%, 促进细根在亚表层土壤中的生长, 比表面积为CK的151%; 覆膜促使黏粒向亚表层土壤移动, 产生明显的淀积粘化作用。土壤物理性黏粒在亚表层土壤中高于表层土壤, 2Y、4Y和6Y处理亚表层土壤物理性黏粒为表层土壤的115.64%、115.58%和114.21%, 呈现土壤紧实化。土壤质地、团聚体特征、有机质含量为主导亚表层土壤退化进程的主要载荷因子, 使根系数量、构型特征受到抑制, 导致长期覆膜(4Y、6Y)苹果细根集中分布于表层土壤中。亚表层土壤中细根变粗、抑制延伸生长、增大导管直径, 以弥补细根数量、形态性状弱化带来的吸收功能减弱, 促使根系采取“密集型”根系构建策略。综上所述,长期覆膜果园亚表层土壤出现物理“隐形”退化, 影响果树根系健康生长和土壤可持续利用。2年为适宜陇东旱塬连续覆膜年限, 生产中应适时揭膜, 促进根系生长、土壤结构优化。

关键词: 覆膜, 细根, 亚表层土壤, 土壤质地, 团聚体稳定性, 主成分分析

Abstract: The Longdong Loess Plateau in Gansu Province is one of the main apple producing areas in China. Plastic film-mulching is often applied to maintain soil moisture as well as water-saving in apple orchards. It is reported that long-term film mulching may cause the degradation of soil physical and chemical properties and inhibition of root growth. The objective of this study were to explore the effect of long-term mulching on the physical and chemical properties, stability of the surface (0–20 cm) and sub-surface (20–40 cm) layer soil, and to investigate the changes of apple fine root growth characteristics in quantity, morphology, configuration and anatomical traits. Methods Using soil profile and stratified sampling method, the changes of the physicochemical properties and soil structural stability of the surface and sub-surface layer soil was analyzed under film-mulching 2 years (2Y), film-mulching 4 years (4Y) and film-mulching 6 years (6Y), conventional tillage (CK) treatments, and roots of 18-year-old apple trees were collected at rapid growing period (days after fruit harvest and before defoliation)to investigate the spatial distribution by measuring the root length, surface area, specific root length, catheter diameter and catheter density. Principal component analysis was used to extract the main factors of root and soil under the condition of plastic film mulching, and to analyze the adaptation strategies for fine root growth of apple trees to the physical degradation of rhizosphere soil. Important findings Short-term film mulching (2Y) treatment significantly improved the soil water content and total porosity in the sub-surface soil layer, increased by 18.04%, 4.53%, respectively, and reduced the soil bulk density by 2.36% than that of conventional tillage (CK) treatments. Growth of fine roots increased in sub-surface soil, and the specific surface area was 151 % of CK. Film mulching promoted the movement of clay particles to the sub-surface soil resulting in obvious deposition and cementation. The physical clay in sub-surface soil was higher than that of surface soil. The physical clay in sub-surface soil under 2Y, 4Y and 6Y mulching were 115.64%, 115.58% and 114.21% of those in surface soil, which led to soil compaction. Soil texture, aggregate characteristics and organic matter content were selected as the main load factors, which dominated degradation process of sub-surface soil, and inhibited the number and configuration characteristics of roots, apple fine roots of long-term film mulching (4Y or 6Y) concentrated in the surface layer of the soil. In the sub-surface soil, fine roots were found to be shortened and coarsened with inhibiting elongation growth and increasing catheter diameter, indicating the ‘intensive’ root construction strategy the offset the weakening of absorption function caused by the fine root quantity and weakening of morphological characteristics. In conlclusion, the ‘invisible’ degradation of sub-surface soil physical property occurred in long-term film mulching orchard will have an influence on healthy roots growth and sustainable soil utilization. It is recommended that 2-year was the suitable for continuous film mulching years in Longdong area, and the mulching film should be removed periodically to promote root growth and optimize soil structure.

Key words: film mulching, fine roots, subsurface soil, soil texture, aggregate stability, principal component analysis