苹果-花生间作系统细根形态变异及地下竞争

Fine-root morphological variation and below-ground competition of an apple-peanut intercropping system

苹果-花生间作系统是晋西黄土区主要的农林复合系统之一,目前一些粗放的经营方式导致苹果和花生之间对地下资源竞争激烈,降低了间作系统的经济效益。为缓解苹果-花生间作系统的种间地下竞争,提出科学的管理实践策略,采用分层挖掘法对苹果-花生间作系统、苹果单作系统和花生单作系统进行根系取样,其中苹果树树龄为7年,苹果树和花生的种植密度分别为500和8万3 333株/hm2。定量研究间作苹果和间作花生细根的形态变异和种间地下竞争状况。结果表明:1)苹果细根主要分布在距苹果树行1. 7 m范围内,随着距苹果树行距离的增加,间作苹果细根生物量密度逐渐减小,而间作花生细根生物量密度逐渐增大,两者的细根生物量密度均在树行南侧大于北侧,且均小于相应的单作; 2)苹果细根主要集中在0～60 cm土壤深度,在20～40 cm土壤深度分布最多,而花生细根集中分布在0～20 cm土壤深度,且间作苹果和间作花生的细根生物量密度在各土层均小于相应单作;3)和单作相比,间作苹果的细根移动到更深的土壤中,而间作花生的细根移动到更浅的土壤中,且两者的细根垂直重心均随着距苹果树行距离的增加向深层土壤移动; 4)间作苹果和间作花生在整个间作区域对地下资源产生竞争,且在苹果树行南侧的种间地下竞争大于北侧,距苹果树行0. 5～1. 7 m区域的苹果-花生间作系统种间地下竞争指数大于0. 53,为种间地下竞争的主要区域。为了有效的缓解苹果和花生之间对地下资源的竞争,花生可以种植在距苹果树行1. 7 m外的区域,并加强间作区域0～20 cm表层土壤的水分和肥料投入,距苹果树行越近,灌溉和施肥可以适当增加,且苹果树行南侧的投入可适当多于北侧。

[Background]Apple-peanut intercropping system is one of the major agroforestry systems on the Loess Plateau of China. However,the extensive management practices for apple-peanut intercropping system leads to intense competition among species for below-ground resources,which results in low overall economic efficiency. To alleviate the interspecific below-ground competition of apple-peanut intercropping system, a scientific basis and technical support for management practices should be investigated. [Methods] A stratified excavation method was performed both to explore the variation of fine-root morphological variation and to quantify the interspecific below-ground competition status of apple-peanut intercropping system and monocropping systems. Among them,the apple trees were planted for 7 years,and the planting densities of apple trees and peanuts were 500 and 83 333 plants/hm2,respectively. Peanut was cultivated at a distance of 0. 5 m from the apple tree row. The area within 0. 5 m of the apple tree row was used for fine-root sampling( 4. 0 m × 4. 0 m) in both the apple-peanut intercropping system and monocropped apple treatments. Three sections( 4. 0 m × 0. 4 m) were randomly selected as the fine-root sampling area in the monocropped peanut treatment. Fine-root dry weight was measured by sampling,while fine-root biomass density,fine-root vertical barycenter and below-ground interspecific competition intensity index were calculated. [Results]1) The fine roots of apple trees were mainly distributed within 1. 7 m from the apple tree row. The farther the section was to the apple tree row,the less the fine-root mass density of the apple trees,while the more the fine-root mass density of the intercropped peanut. The fine-root mass density of both apple trees and intercropped peanut of the northern apple tree row was greater than that of the southern,and the fine-root biomass density of the intercropped apple trees and intercropped peanut were less than that of the monocropping systems. 2)The fine roots of apple trees concentrated mostly within the soil depths of 0-60 cm,and those of apple trees and peanut were distributed mostly within the 20-40 cm and 0-20 cm soil depth,respectively.Compared with that in the monocropping systems,the fine-root mass density of the intercropped apple trees and peanut decreased in each soil layer. 3) Compared with that of the monocropping systems,the fine-root vertical barycenter of the intercropped apple trees displaced deeper soil,and the fine-root vertical barycenter of the peanut displaced shallower soil;the fine-root vertical barycenter of both apple trees and peanut displaced deeper soil with distance from the apple tree row. 4) The components of the apple-peanut intercropping system competed for soil water and nutrients at distances 0. 5-2. 5 m from the apple tree row. The interspecific below-ground competition intensity was slightly greater in the south of a apple tree row than the north of a row. The interspecific below-ground competition index of the applepeanut intercropping system in the 0. 5-1. 7 m area of apple trees was greater than 0. 53,which was the main area of interspecific below-ground competition. And a relatively greater intensity of below-ground interspecific competition in the apple-peanut intercropping system for soil water and nutrients occurred within distances of 0. 5-1. 7 m from the apple tree row. [Conclusions] To effectively alleviate the below-ground interspecific competition in apple-peanut intercropping system and obtain more production,farmers should appropriately increase the distance between peanut and apple tree rows. Peanut should be planted in areas at distances of 1. 7 m away from apple tree rows. Furthermore,farmers should also increase water and fertilizer input within the 0-20 cm soil layer in intercropping area. Irrigation and fertilization can be appropriately increased with the distance from the apple tree row;in addition,input in the south side of an apple tree row should be slightly greater than those in the north side of the row.