Combined zinc and nitrogen applications at panicle initiation for zinc biofortification in rice

Background and purpose: Increasing zinc (Zn) concentration in rice grains can help improve Zn nutrition of people. The combinations of Zn and nitrogen (N) applications at panicle initiation were investigated for Zn biofortification in rice. Materials and methods: Rice (cv. Super Basmati) seedling were grown in pots having a calcareous soil. All possible combinations of four Zn (control, Soil 6 mg Zn kg–1, foliar 2 × 0.2% Zn and soil + foliar Zn) and three N (control, soil 20 mg N kg–1 and foliar 0.5% N) levels were imposed at panicle initiation. At maturity, grains were analysed for Zn and proteins. Results: Grain protein concentration was significantly increased with foliar Zn treatments, and with soil and foliar N. Maximum grain Zn concertation (30 mg kg–1) was achieved with application of soil Zn + foliar Zn + foliar N. At each N level, Zn application by either method significantly increased grain Zn concentration over control. This increase in grain Zn concertation at N levels was 36 to 54% with soil Zn + foliar Zn, 27 to 45% with foliar Zn and 9 to 15% with soil Zn over its control level. Conclusions: Grain Zn concentration was significantly increased with soil N when combined with soil Zn, and with foliar N when combined with foliar Zn treatments. Conclusively, foliar N combined with soil + foliar Zn is the best combination of late Zn and N application for agronomic Zn biofortification in rice.