TITLE:
Impact of Nitrogen and Zinc Fertilizers on the Synthesis of Functional Compounds during Seed Development in Various Types of Purple Rice
AUTHORS:
Suchila Utasee, Sansanee Jamjod, Jeeraporn Veeradittakit, Chanakan Prom-u-Thai
KEYWORDS:
Purple Rice, Pigmented Rice, Functional Compounds, Bioactive Compounds, Fertilization
JOURNAL NAME:
Agricultural Sciences,
Vol.16 No.10,
October
11,
2025
ABSTRACT: The study evaluated total anthocyanin, phenol, and DPPH activity during seed development in two traditionally improved and one modern improved purple rice varieties under varying nitrogen (N) and zinc (Zn) applications. Two N levels were tested: 120 kg N/ha (N120) and no N application (N0). Three Zn application methods were applied: (1) no Zn fertilizer (Zn0), (2) soil Zn application at 50 kg ZnSO4/ha (ZnS), and (3) foliar Zn application at 0.5% ZnSO4 (800 L/ha) (ZnF), with foliar Zn applied twice at flowering and 10 days after flowering. The seeds were randomly collected at 7, 14, 21, 28, and 35 (fully maturity) days after flowering (DAF). This study observed variations in seed appearance as affected by N and Zn application during development among different purple rice varieties. The darkest pericarp color was found when ZnF was applied with N120. The concentration of grain anthocyanin, phenol, and DPPH activity was synthesized at 7 DAF, peaked at 14 DAF, and gradually declined until maturity at 35 DAF. At early seed developing, applying ZnS under N0 yielded as high total anthocyanin, phenol, and DPPH activity as for applying ZnF under N120. At maturity, applying N120 with ZnF established the highest grain anthocyanin, phenol, and DPPH activity compared with the others. Therefore, grain anthocyanin, phenol, and DPPH activity in purple rice varieties can be enhanced through N and Zn fertilization from early seed development to maturity, especially at 14 DAF, soil Zn application without N (N0 + ZnS) yielded total anthocyanin, phenol, and DPPH activity levels comparable to the high input N120 + ZnF. However, the optimal Zn application method, combined with N, should be carefully considered at each seed developing and rice variety to maximize value for both farmers and consumers.