Effects of Wheat Root Morphologies on Agricultural Soil Gas Fluxes

Agricultural lands comprise ~40% of European land and significantly contribute to continental greenhouse and trace gas emissions¹, particularly nitrous oxide (N₂O), and reactive nitrogen species including ammonia (NH₃) and nitrogen oxides (NO_x, NO_z). Within the EU's commitment to reduce agricultural greenhouse gas emissions by 30% by 2030, understanding crop variety influences on these emissions is crucial. While the release of nitrogenous gases following synthetic nitrogen (N) fertiliser application is well-documented, the impact of crop traits on emission patterns through their effects on soil properties and microbial communities remains poorly understood. Wheat, as Europe's dominant cereal crop and a global food security cornerstone, has undergone extensive breeding resulting in distinct heritage and modern semi-dwarf varieties.² These varieties differ primarily in their expression of reduced height genes, which were introduced to support higher grain yields but consequently altered root system biomass allocation and morphology.³ Here, we present the first comprehensive assessment of how these root architectural differences influence soil N-cycling and subsequent gas emissions. Our field trials, conducted in central England, compared two heritage varieties (Red Lammas and Chidham Red) with two semi-dwarf varieties (Crusoe and Skyfall) under different N fertiliser treatments (0, 60, and 120 kg-N ha^-1). Continuous gas flux measurements using multiplexed chambers coupled with FTIR spectroscopy and chemiluminescence detectors revealed >600% higher nitric oxide (NO) emissions from modern varieties during spring. Molecular analyses of rhizosphere soil showed distinct N-cycling microbial communities between variety types (Fig. 1). Seasonal dynamics indicated strongest variety effects during summer fertiliser application and early spring moisture stress periods. This research directly informs European agricultural policy by demonstrating how historical breeding decisions influence greenhouse gas emissions, while providing evidence-based strategies for variety selection and fertiliser management that could reduce agricultural nitrogen losses without compromising yield targets.

Figure 1. Predicted gene counts of microbes associated with denitrification and nitrification from rhizosphere soil of higher specific root length (SRL) taller cultivars and lower SRL semi-dwarf cultivars of wheat, quantified using shotgun DNA sequencing.

 

(1)        Tubiello, F. N.; Salvatore, M.; Rossi, S.; Ferrara, A.; Fitton, N.; Smith, P. The FAOSTAT Database of Greenhouse Gas Emissions from Agriculture. Environ. Res. Lett. 2013, 8 (1), 015009. https://doi.org/10.1088/1748-9326/8/1/015009.

(2)        Shewry, P. R. Wheat. Journal of Experimental Botany 2009, 60 (6), 1537–1553. https://doi.org/10.1093/jxb/erp058.

(3)        Vergauwen, D.; De Smet, I. From Early Farmers to Norman Borlaug — the Making of Modern Wheat. Current Biology 2017, 27 (17), R858–R862. https://doi.org/10.1016/j.cub.2017.06.061.