Effects of Zn fertilizer types and application methods on grain yield and zn concentration of rice

Objectives There is a general recognition that zinc (Zn) fertilizer application could increase grain yield and grain Zn concentration of rice in Zn deficiency soils. A normal rice variety Jiponica material was used in order to investigate the effects of different Zn fertilizer types and application methods on rice yield, Zn concentration and accumulation in individual organs of rice 'Zhendao 11'.

Methods During May 2011 and November 2012, four experiments were carried out in the field. Experiment 1 was conducted with Zn-enriched rice grain with normal planting (CK) and 5 times spray of ZnSO₄·7H₂O (Zn) as treatment, in order to investigate the grain Zn concentration by staining. Experiment 2 studied different Zn fertilizers which included control (S1), ZnSO₄·7H₂O (S2), Urea-Zn (S3), Mosaic-Zn (S4), Kali-Zn (S5), transplanting Zn-enriched seedling (S6) and seedling root dip ZnSO₄·7H₂O solution before transplanting (S7) treatments. Experiment 3 was applying different Zn fertilizers by foliar spray, included control (F1), spray ZnSO₄·7H₂O at booting stage (F2), spray ZnSO₄·7H₂O at flowering stage (F3), ZnSO₄·7H₂O at booting and flowering (F4), ZnSO₄·7H₂O at flowering with pesticide (F5), Kali-EPSO-Zn spray (F6) and ADOB-IDHA-Zn spray (F7) treatments. Experiment 4 aimed to evaluate the growth performance of Zn-enriched rice grain (Zn-grain) and normal rice grain (CK-grain) and the grain yield, Zn concentration and its accumulation in different organs of rice.

Results 1) The Zn-enriched rice grain can be produced by intensive foliar spray of high concentration of Zn fertilizer in rice growth stages, and the DTZ staining method can be used as a rapid method to estimate Zn concentration in grain. 2) Zn fertilizer application significantly increased the yield and Zn content in rice crops, and there were significant differences among the Zn fertilizer types and application methods. 3) The average yield of rice in treatment with Zn fertilizer used as soil application was significantly higher than that of foliar application (by 6.2%), while the Zn contents of leaf, stem and grain in foliar treatment were significantly higher than those of soil application (by 224.6%, 78.5% and 12.1%, respectively). 4) The increase rate of yield in treatment with complex fertilization of Zn and N or K treatments was significantly higher than the treatment with Zn and P under soil application, while in foliar application the Zn content was increased in Kali-EPSO-Zn treatment, which was significantly higher than that of ADOB-IDHA-Zn and ZnSO₄·7H₂O treatments. 5) The rice yield and grain Zn concentration were increased by 4.6% and 3.9% when planting the Zn-enriched rice grain (Zn-grain) compared with normal rice grain (CK-grain), respectively.

Conclusions Application of Zn fertilizer to the soil was more effective than the foliar spray on rice grain yield; however, the foliar spray resulted in a greater increase in grain Zn concentration, when compared with soil application. Therefore, according to local conditions, integrated application of Zn fertilizers as soil application (N and Zn compound fertilizer) with foliar spray (K and Zn compound fertilizer) on selected Zn-enriched rice grain is the best strategy to achieve optimal Zn use efficiency, to maximum yield and to improve the Zn nutritional quality of rice.