Soil Zinc Availability Alters the Contribution of Pre-Anthesis and Post-Anthesis Uptake in Rice Grain Zinc Loading

Rice (Oryza sativa L.) is the most crucial cereal globally and serves as a vital source of zinc (Zn) for individuals whose diets are primarily rice-based. To improve the Zn content in rice, it is essential to gain a deeper understanding of how plants absorb and distribute zinc internally. This research investigated how different rates of soil Zn fertilization (0, 3, 6, 9, 12, and 15 kg Zn ha−1) impacted the growth, yield, zinc uptake, and remobilization in the non-aromatic rice genotype '10/B-2-1', cultivated in Zn-deficient soil. The findings indicated that zinc application had a notable influence on rice yield and related parameters, except for the tiller count per plant and panicle length. The concentration and accumulation of zinc at both anthesis and maturity showed significant increases, particularly at higher zinc rates (9, 12, and 15 kg Zn ha−1) compared to the control. Over 85% of the zinc accumulated at maturity came from uptake prior to anthesis. Additionally, the efficiency of zinc remobilization dropped from 22.28% in the control to 10.88% at the highest zinc application of 15 kg Zn ha−1. The proportion of grain zinc derived from remobilization significantly decreased from 65.66% to 40.29% as zinc levels rose from 0 to 15 kg Zn ha−1, highlighting the critical role of post-anthesis uptake in grain Zn loading when zinc availability is higher. Moreover, it was evident that post-anthesis uptake was the principal source of grain Zn when AB-DTPA extractable zinc concentrations exceeded 1.0 mg kg−1, while pre-anthesis remobilization prevailed at lower soil zinc concentrations. The results of study warrant further investigations involving larger number of genotypes on diverse soil types.