Content Patterns of Maize Endogenous Hormones and Grain Yield Influenced by Field Phosphorus Application

The content of plant endogenous hormones could be influenced by fertilization, which play an important regulatory role in plant growth and yield formation. However, the effects of phosphate (P) application rates on the dynamical changes in the exogenous hormone content in maize plants to support high-yield production are still unclear. An experiment with six P application rates was designed (P1, 0 kg ha⁻¹; P2, 20 kg ha⁻¹; P3, 40 kg ha⁻¹; P4, 60 kg ha⁻¹; P5, 80 kg ha⁻¹; and P6, 100 kg ha⁻¹), aimed at determining the distribution or biosynthesis of phytohormones in maize roots and leaves, and clarifying the role of P fertilization in the formation of phytohormones. The results showed that P fertilization significantly increased the content of IAA, by 51.57%, and significantly decreased the contents of ABA and GA3, by 18.92% and 19.13% on average compared to P1. The highest increase in IAA was 99.02%, and the highest decreases in ABA and GA3 were 32.30% and 26.85%, respectively, in the P6 treatment in maize roots. Meanwhile, an increase in the IAA (41.34%), SA (27.58%), and GA3 (37.36%) contents and a decrease in the ABA (19.18%) content in maize leaves were observed. The highest increases in IAA, GA3, and SA in the P6 treatment in maize leaves were 57.5%, 62.50%, and 48.57%, respectively, and the highest decrease in ABA was 28.05%. Meanwhile, different contents of endogenous hormones in maize roots and leaves were observed at various maize growth stages. The maize phenotypes and soil available P content were increased with P application as well. A Pearson’s correlation analysis showed that endogenous hormones were significantly correlated with maize phenotypes and yield. Our results confirmed that P fertilization could change the content of endogenous hormones in maize roots and leaves; P6 was the best treatment for improving the endogenous hormone contents in maize plants, P3 was the best for improving the maize grain yield. Overall, 40 kg ha⁻¹ is recommended as the best P application rate under the experimental conditions, considering the economic cost and environmental effects.