A teosinte and modern maize hybrid use different carbon allocation strategies in response to cover crop residue nitrogen

With a growing focus on soil health, modern agroecosystems have begun to emphasize greater reliance on organic nitrogen (N) sources to meet crop N demands. Teosinte (Zea mays subsp. parviglumis), a wild relative of modern maize (Zea mays subsp. mays), is believed to modulate its belowground carbon (C) allocation based on the type of N in the soil, thus allowing for greater organic N uptake. However, linkages between belowground allocation and N acquisition from organic vs. synthetic N sources remain poorly understood.

We designed a ¹³C/¹⁵N dual label experiment in which we compared the C allocation patterns of modern maize and teosinte in response to synthetic (urea) and organic (cover crop residue) forms of N.

Teosinte responded to organic N by increasing its biomass root-to-shoot (R:S) ratio by 50% compared to synthetic N, while modern maize maintained the same biomass R:S ratios in both N treatments. Recent photosynthate R:S ratio (measured using ¹³C-CO₂, 7 weeks after establishment) was greater in organic N than in synthetic N treatments for both modern maize and teosinte (91% and 37%; respectively). Label-derived dissolved organic C, representing recent rhizodeposits, was 2.5 times greater in the organic N treatments for both genotypes.

Modern maize took up a similar amount of organic N as teosinte using different C allocation strategies. Our findings suggest that intensive breeding under high N input conditions has not affected this modern maize hybrid’s access to organic N while improving its ability to take up synthetic N.