Deep-rooted perennial crops differ in capacity to stabilize C inputs in deep soil layers
Leanne Peixoto, Jørgen E. Olesen, Lars Elsgaard, Kirsten Lønne Enggrob, Callum C. Banfield, Michaela A. Dippold, Mette Haubjerg Nicolaisen, Frederik Bak, Huadong Zang, Dorte Bodin Dresbøll, Kristian Thorup‐Kristensen, Jim Rasmussen
Abstract
Abstract Comprehensive climate change mitigation necessitates soil carbon (C) storage in cultivated terrestrial ecosystems. Deep-rooted perennial crops may help to turn agricultural soils into efficient C sinks, especially in deeper soil layers. Here, we compared C allocation and potential stabilization to 150 cm depth from two functionally distinct deep-rooted perennials, i.e., lucerne ( Medicago sativa L.) and intermediate wheatgrass (kernza; Thinopyrum intermedium ), representing legume and non-legume crops, respectively. Belowground C input and stabilization was decoupled from nitrogen (N) fertilizer rate in kernza (100 and 200 kg mineral N ha −1 ), with no direct link between increasing mineral N fertilization, rhizodeposited C, and microbial C stabilization. Further, both crops displayed a high ability to bring C to deeper soil layers and remarkably, the N 2 -fixing lucerne showed greater potential to induce microbial C stabilization than the non-legume kernza. Lucerne stimulated greater microbial biomass and abundance of N cycling genes in rhizosphere soil, likely linked to greater amino acid rhizodeposition, hence underlining the importance of coupled C and N for microbial C stabilization efficiency. Inclusion of legumes in perennial cropping systems is not only key for improved productivity at low fertilizer N inputs, but also appears critical for enhancing soil C stabilization, in particular in N limited deep subsoils.