Seed Priming and Foliar Application with Nitrogen and Zinc Improve Seedling Growth, Yield, and Zinc Accumulation in Rice

Improving grain yield and zinc (Zn) concentration yields a double benefit for farmers and consumers, especially when accomplished through the common practice of nitrogen (N) and Zn application. The objective of this study was to evaluate responses of a modern improved rice variety (SPT1) to Zn and N fertilizer management of seed germination, seedling growth, yield, and grain Zn accumulation. A preliminary laboratory study was conducted by priming seeds with variation of N and Zn solutions, consisting of (1) 0% urea + 0% ZnSO 4 (N0Zn0), (2) 0% urea + 0.07% ZnSO 4 (N0Zn+), (3) 0.05% urea + 0.07% ZnSO 4 (N0.05Zn+), (4) 0.10% urea + 0.07% ZnSO 4 (N0.10Zn+), (5) 0.15% urea + 0.07% ZnSO 4 (N0.15Zn+), (6) 0.20% urea + 0.07% ZnSO 4 (N0.20Zn+), and (7) 0.25% urea + 0.07% ZnSO 4 (N0.25Zn+). Priming seeds with N0.15Zn+ led to a higher germination rate and growth performance. Seedling Zn concentration increased linearly along with the dry weights of root and coleoptile during germination. A second experiment in the field included priming the seed with (1) 0% urea + 0% ZnSO 4 (N0Zn0), (2) 0.15% urea + 0% ZnSO 4 (N+Zn0), (3) 0% urea + 0.07% ZnSO 4 (N0Zn+), and (4) 0.15% urea + 0.07% ZnSO 4 (N+Zn+); this experiment showed that simultaneous priming of seeds with 0.15% urea and 0.07% ZnSO 4 (N+Zn+) resulted in the highest coleoptile length and seedling dry weight. The highest seedling Zn concentration was observed when priming seeds with N0Zn+ followed by N+Zn+, but the effect disappeared at the later growth stages. A third experiment in the field was conducted by foliar application with four different treatments of (1) 0% urea + 0% ZnSO 4 (N0Zn0), (2) 1% urea + 0.5% ZnSO 4 (N+Zn0), (3) 0% urea + 0.5% ZnSO 4 (N0Zn+), and (4) 1% urea + 0.5% ZnSO 4 (N+Zn+). The highest grain yield increases were achieved by foliar application of N+Zn0 (28.5%) and foliar application of N+Zn+ (32.5%), as compared with the control (N0Zn0). Grain Zn concentration was the highest under foliar application of N+Zn+, with a 37.9% increase compared with N0Zn0. This study confirmed that seedling growth performance can be enhanced by initially priming seeds with N and Zn solution, while grain yield and Zn concentration can be improved by foliar application of N and Zn fertilizer. The information would be useful for the appropriate combined application of Zn and N fertilizers in the practical field to improve grain yield and Zn accumulation as well as Zn nutrition among humans with rice-based diets. The result should be extended to a wider range of rice varieties under suitable management of N and Zn fertilizer.