Optimizing Water and Nitrogen Management Improves Maize Productivity by Regulating Root Development

Abstract

Water constraints and excessive nitrogen (N) application hinder root development, reducing the growth and yield of summer maize in cold semi-arid regions (CSR). Optimizing water-N interactions could enhance root distribution and nutrient absorption, which is crucial for achieving high crop yields. This study aimed to determine the optimal water-N interaction conditions for CSR, while enhancing their impact on the root physiological growth characteristics and yield of summer maize. The two-year (2020-2021) experiment included three N application rates (N0: 0 kg ha-1, N100: 100 kg ha-1, N200: 200kg ha-1, N300: 300 kg ha-1) and three water conditions (S1: 40%, S2: 60%, S3: 80% field water capacity). S3-N200 increased plant height (7.89%), stem thickness (10.48%), and ear position height (5.14%) compared to S3-N300, and substantially boosted antioxidant enzymes in the root (7.72%), lowering reactive oxygen species (11.81%) and raising K+ (18.22%), Ca2+ (16.35%), Mg2+ (20.01%), and reduced Na+ (3.83%) levels. Similarly, S3-N200 increased Indole-3-acetic acid (IAA), Gibberellins (GAs), and Zeatin + zeatin riboside (Z+ZR) by 45%, 43%, and 30%, respectively, compared to S3-N300, and increased biomass accumulation (spike: 11.98%; leaf: 23.21%; stalk:16.63%; grain: 6.95%) and maize yield by 8.01%. Structural equation modeling (SEM) elucidated that maize yield, ion content, endogenous hormone levels, and ROS generated by varied water-N interactions were explained by 94%, 89%, 94%, and 91%, respectively. The S3-N200 interaction regulates the root system, thereby enhancing maize resilience to adverse conditions and facilitating nutrient absorption. Consequently, this enhancement promotes maize growth and yield, highlighting the importance of effective water-N management for agricultural productivity. Identify optimal water-N interaction for North China's CSR, optimize N application for water efficiency, and achieve sustainable increases in maize production to provide a strong foundation for farmers.

Keywords: maize, enzymes, crop yield, nitrogen, root development, water stress