Evidence of considerable C and N transfer from peas to cereals via direct root contact but not via mycorrhiza

Abstract

Intercropping of legumes and cereals is an important management method for improving yield stability, especially in organic farming systems. However, knowledge is restricted on the relevance of different nutrient transfer pathways. The objective of the study was to quantify nitrogen (N) and carbon (C) transfer from peas to triticale by (1) direct root contact (= R), (2) arbuscular mycorrhizal fungi (AMF; = A), and (3) diffusion (= D). Pea (Pisum sativum cv. Frisson and P2) and triticale (Triticum × Secale cv. Benetto) plants as intercrop were grown for 105 days. Treatment ADR enabled all transfer paths between the two crops. Treatment AD with root exclusion enabled AMF and diffusion transfer between peas and triticale. Treatment A with a diffusion gap barrier only allowed AMF transfer. Pea plants were labelled every 14 days with a 13C glucose and 15N urea solution, using the cotton wick technique. Direct root contact resulted in the highest pea rhizodeposition and thus the largest absolute amounts of N and C transfer to triticale. Root exclusion generally changed composition of rhizodeposits from fine root residues towards root exudates. Pea plant-N consisted of 17% N derived from rhizodeposition (NdfR) in treatment ADR but only 8% in the treatments AD and A, independently of pea variety, whereas pea plant-C consisted of 13% C derived from rhizodeposition (CdfR), without pea variety and transfer path treatment effects. Averaging all transfer path treatments, 6.7% of NdfR and 2.7% of CdfR was transferred from Frisson and P2 to triticale plants. Approximately 90% of this NdfR was transferred by direct root contact from Frisson to triticale and only 10% by AMF, whereas only 55% of CdfR was transferred to triticale by direct root contact, 40% by AMF and 5% by diffusion. Similar percentages were transferred from mutant P2 to triticale. Root exclusion generally changed RD composition from fine root residues towards root exudates.

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

“…In this experiment, the NTA from soybean to cotton increased with the weakening of the root barrier, due to the larger contact areas of root between the species. A main reason for the high NTA of direct root contact was resource complementarity between nonlegumes and legumes, which promotes interspecific N uptake directly by specific root exudates or indirectly by induced microbial activity 47‐49 . Notably, this study showed that the cotton with the NB treatment had greater RDWD, RLD, and root angle than with the CB and SB treatments, which promoted absorption and transfer of soil moisture and nutrients 50 …”

“…A main reason for the high NTA of direct root contact was resource complementarity between nonlegumes and legumes, which promotes interspecific N uptake directly by specific root exudates or indirectly by induced microbial activity. [47][48][49] Notably, this study showed that the cotton with the NB treatment had greater RDWD, RLD, and root angle than with the CB and SB treatments, which promoted absorption and transfer of soil moisture and nutrients. 50 In this experiment, we found that, although the growth of soybean root was negatively correlated with the NTA treatment, the size of the effect of NTA on soybean was greater than its effect on cotton, mainly because soybean had more powerful lateral roots to regulate the soil environment.…”

Assessment of nitrogen fertilization in cotton/soybean intercropping using the 15N isotope dilution method

“…The competition for N among species was weakened under higher soil N, with plants meeting their own growth without relying on N transfer (Yong et al, 2015). Generally, the absorption capacity of N of legumes was weaker than that of associated crops, while the roots of legumes decompose faster because of the low C/N ratio (Hupe et al, 2021). Therefore, the root turnover of legumes in the intercropping system provides a pathway for N transfer.…”

Forage yield and biological nitrogen fixation of pea–cereal intercrops for hay production

“…Studies on intercropping systems suggest that plants may acquire N directly from companion plants through in-season N transfer (Johansen & Jensen, 1996). In a recent study, Hupe et al (2021) reported that direct root contact resulted in high pea rhizodeposition, and thus the large amount of N transfer to triticale (×Triticosecale Wittm. ex A. Camus).…”

“…In a recent study, Hupe et al. (2021) reported that direct root contact resulted in high pea rhizodeposition, and thus the large amount of N transfer to triticale ( ×Triticosecale Wittm . ex A. Camus).…”