Variation of Fine Roots Distribution in Apple (Malus pumila M.)–Crop Intercropping Systems on the Loess Plateau of China

Abstract

In arid and semi-arid areas, interspecific below-ground competition is prominent in agroforestry systems. To provide theoretical and technical guidance for the scientific management of apple–crop intercropping systems, a field study was conducted in the Loess Plateau of China to examine the variation of fine roots distribution in apple–crop intercropping systems. The fine roots of apple trees and crops (soybean (Glycine max (L.) Merr) or peanuts (Arachis hypogaea Linn.)) were sampled to 100 cm depth at ten distances from the tree row using the stratified excavation method. The results showed that the vertical distribution of fine roots between intercropped apple trees and intercropped crops were skewed and overlapped. Apple–crop intercropping inhibited the fine roots of apple trees in the 0–60 cm soil depth, but promoted their growth in the 60–100 cm soil depth. However, apple–crop intercropping inhibited the fine roots of intercropped crops in the 0–100 cm soil depth. For the fine roots of each component of the apple–crop intercropping systems, variation in the vertical distribution was much greater than variation in the horizontal distribution. Compared with monocropped systems, apple–crop intercropping caused the fine roots of intercropped apple trees to move to deeper soil, and those of intercropped crops to move to shallower soil. Additionally, apple–crop intercropping slightly inhibited the horizontal extension of the fine-root horizontal barycentre (FRHB) of intercropped apple trees and caused the FRHB of intercropped crops to be slightly biased towards the north of the apple tree row. Variation of the fine roots distribution of each component of the apple–soybean intercropping system was greater than that of the apple–peanut intercropping system. Thus, the interspecific below-ground competition of the apple–peanut intercropping system was weaker than that of the apple–soybean intercropping system. Intense competition occurred in the apple–peanut intercropping system and the apple–soybean intercropping system was in sections whose distance ranged from 0.5–1.3 and 0.5–1.7 m from the tree row, respectively. The interspecific below-ground competition was fiercer on the south side of the apple tree row than on the north side.

Root traits with team benefits: understanding belowground interactions in intercropping systems

“…In tree-based alley cropping systems, the fine roots of the intercropped trees seem to extend into deeper soil layers, while the fine roots of the intercropped annual crops remain in shallower soil compared with the respective monocultures: this was the case for apple (Malus pumila M.) intercropped with either soybean or peanut (Sun et al 2018). Apple-annual crop intercropping inhibited growth of the fine roots of apple trees in the 0-60 cm soil depth, reducing fine root density by 25-35%, while fine root density in the 60-100 cm soil layer was unchanged compared to the monoculture; by contrast, fine root density of the intercropped soybean or peanut was reduced throughout the soil profile (Sun et al 2018). In a study of annual crops, the fine roots of maize intercropped with several legumes were found to be more homogeneously distributed down the soil profile than in the maize monoculture, with 50% of fine roots located in the 0-36 cm soil layer in the intercrop and in the 15-21 cm soil depth in monocultures (Neykova et al 2011).…”

Effects of poplar intercropping systems on reducing the concentration of different forms of inorganic nitrogen in the soil profile

“…Thus, the inorganic nitrogen reduction was significantly greater in the topsoil than in the other soil layers. The overlapping area of dense root distribution between poplar and wheat is caused by soil fertility, soil water content (Duan et al, 2019; Wu et al, 2016), tree age (B. J. Wang et al, 2014; Zhang et al, 2019), crop species (Makumba et al, 2009; Sun et al, 2018a), tree species (Borden et al, 2017), and tree and crop planting density (Y. F. Wang et al, 2018). However, there was an increase in the HACRs in the 40–60 cm soil layer in and and in the 20–40 cm soil layer in in the PWN and PWW systems (Figure 5).…”

15N labeling technology reveals enhancement of nitrogen uptake and transfer by root interaction in cotton/soybean intercropping

“…Legumes are ideal companion crops in intercropping systems, and intercropping between legumes and other crops has been widely applied 14 . Root interaction plays an important role in yield formation in the intercropping system with legumes, 15 which causes the soil nutrients and moisture become heterogeneous 16,17 . In turn, complex nutrient and moisture transport in intercropping systems with legumes have a significant impact on root configuration 18 .…”