Nitrogen uptake and transfer in a soybean/maize intercropping system in the karst region of southwest China

Abstract

Nitrogen (N) deficiency occurs in over 80% of karst soil of southwest China, which restricts regional agricultural production. To test whether N fixed by legumes becomes available to nonfixing companion species, N fluxes between soybean and maize under no, partial, and total restriction of root contact were measured on a karst site in southwest China. N content and its transfer between soybean and maize intercrops were explored in a 2‐year plot experiment, with N movement between crops monitored using 15N isotopes. Mesh barrier (30 μm) and no restrictions barrier root separation increased N uptake of maize by 1.28%–3.45% and 3.2%–3.45%, respectively. N uptake by soybean with no restrictions root separation was 1.23 and 1.56 times higher than that by mesh and solid barriers, respectively. In the unrestricted root condition, N transfer from soybean to maize in no restrictions barrier was 2.34–3.02 mg higher than that of mesh barrier. Therefore, it was implied that soybean/maize intercropping could improve N uptake and transfer efficiently in the karst region of southwest China.

Root Contact between Maize and Alfalfa Facilitates Nitrogen Transfer and Uptake Using Techniques of Foliar 15N-Labeling

“…In addition, the total biomass and the N uptake with no root barrier were significantly higher than those with the nylon net barrier. In conclusion, the root contact plays an important role in intercropping [14]. However, the maize/alfalfa intercropping system has no commercial applicability.…”

“…The main reason for the high nitrogen transfer with no N barrier may be that the close root contact of maize and alfalfa can stimulate the plants to release more N-containing compounds or generate more mycelial connections between the legume and the cereal plants [21]. Moreover, root contact reduces the travel distance of N compounds through mass flow [31], which efficiently promotes N transfer in soybean/maize intercropping systems [14]. In addition, root morphology and biomass influence the uptake and the utilization of soil water and nutrients and permit subsequent N transfers between cereals and legumes [23].…”

“…These benefits occur because N transfer between legumes and cereals can be an important source of nitrogen for cereal crops [7,8]. N transfer has been studied thoroughly in many cereal-legume intercropping systems, e.g., bean/maize [9], pea/barley [10], faba/wheat [11], peanut/rice [7], manures/lettuce [12], pea/maize [13], soybean/maize [14], and bean/garlic [15]. Literature data show that rates of N transfer range from 0 to 80% from legumes to cereal in mixed stands, depending on the legume species and the cultivar [16][17][18].…”

“…One study revealed that root contact improved N uptake by 26.3% [24]. Zhang et al found that soybean/maize intercropping could improve N transfer and uptake in the karst region of Southwest China [14]. However, it is unclear whether the high nitrogen transfer is associated with the total N uptake under maize/alfalfa root contact conditions.…”

Developing sugarcane - legume companion cropping systems to minimise nitrous oxide emissions

“…shown the importance of root interaction to enhance the direct N transfer via root exudates in a maize-faba bean intercrop (Li et al, 2016) or via mycorrhizal hyphae network that increased direct N transfer from soybean to maize from 13.2 to 30.2% (Zhang et al, 2017). Mycorrhizas were not quantified in the current study, although the presence of soil may have provided mycorrhizal spores.…”