Interaction Effects of Nitrogen Rates and Forms Combined With and Without Zinc Supply on Plant Growth and Nutrient Uptake in Maize Seedlings

Yanfang Xue; Wei Yan; Yingbo Gao; Hui Zhang; Liping Jiang; Xin Qian; Zhenling Cui; Chunyan Zhang; Shutang Liu; Huimin Wang; Zongxin Li; Kaichang Liu

doi:10.3389/fpls.2021.722752

Interaction Effects of Nitrogen Rates and Forms Combined With and Without Zinc Supply on Plant Growth and Nutrient Uptake in Maize Seedlings

Front Plant Sci. 2021 Dec 9:12:722752. doi: 10.3389/fpls.2021.722752. eCollection 2021.

Authors

Yanfang Xue¹, Wei Yan¹, Yingbo Gao¹, Hui Zhang¹, Liping Jiang^{1

2}, Xin Qian¹, Zhenling Cui^{1

3}, Chunyan Zhang⁴, Shutang Liu², Huimin Wang¹, Zongxin Li¹, Kaichang Liu¹

Affiliations

¹ National Engineering Laboratory of Wheat and Maize, Key Laboratory of Biology and Genetic Improvement of Maize in Northern Yellow-Huai Rivers Plain, Ministry of Agriculture, Maize Research Institute, Shandong Academy of Agricultural Sciences, Jinan, China.
² College of Resources and Environment, Qingdao Agricultural University, Qingdao, China.
³ College of Resources and Environment, China Agricultural University, Beijing, China.
⁴ Linyi Academy of Agricultural Sciences, Linyi, China.

Abstract

Previous studies have shown that zinc (Zn) accumulation in shoot and grain increased as applied nitrogen (N) rate increased only when Zn supply was not limiting, suggesting a synergistic effect of N on plant Zn accumulation. However, little information is available about the effects of different mineral N sources combined with the presence or absence of Zn on the growth of both shoot and root and nutrient uptake. Maize plants were grown under sand-cultured conditions at three N forms as follows: NO₃ ^- nutrition alone, mixture of NO₃ ^-/NH₄ ⁺ with molar ratio of 1:1 (recorded as mixed-N), and NH₄ ⁺ nutrition alone including zero N supply as the control. These treatments were applied together without or with Zn supply. Results showed that N forms, Zn supply, and their interactions exerted a significant effect on the growth of maize seedlings. Under Zn-sufficient conditions, the dry weight (DW) of shoot, root, and whole plant tended to increase in the order of NH₄ ⁺ < NO₃ ^- < mixed-N nutrition. Compared with NH₄ ⁺ nutrition alone, mixed-N supply resulted in a 27.4 and 28.1% increase in leaf photosynthetic rate and stomatal conductance, which further resulted in 35.7 and 33.5% of increase in shoot carbon (C) accumulation and shoot DW, respectively. Furthermore, mixed-N supply resulted in a 19.7% of higher shoot C/N ratio vs. NH₄ ⁺ nutrition alone, which means a higher shoot biomass accumulation, because of a significant positive correlation between shoot C/N ratio and shoot DW (R ² = 0.682^***). Additionally, mixed-N supply promoted the greatest root DW, total root length, and total root surface area and synchronously improved the root absorption capacity of N, iron, copper, manganese, magnesium, and calcium. However, the above nutrient uptake and the growth of maize seedlings supplied with NH₄ ⁺ were superior to either NO₃ ^- or mixed-N nutrition under Zn-deficient conditions. These results suggested that combined applications of mixed-N nutrition and Zn fertilizer can maximize plant growth. This information may be useful for enabling integrated N management of Zn-deficient and Zn-sufficient soils and increasing plant and grain production in the future.

Keywords: interaction effects; maize; nitrogen rates and forms; nutrient uptake; root morphology; zinc supply.