Date of Graduation

5-2019

Document Type

Thesis

Degree Name

Master of Science in Crop, Soil & Environmental Sciences (MS)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Slaton, Nathan A.

Committee Member

Mason, Richard E.

Second Committee Member

Gbur, Edward E. Jr.

Third Committee Member

Burgos, Nilda R.

Fourth Committee Member

Willett, Cammy D.

Keywords

Zinc sulfate; Zinc fertilization; Non-fortified rice seed

Abstract

Zinc (Zn) is the most common micronutrient deficiency in flooded rice (Oryza sativa L.). Some new Zn fertilization methods have been advertised, but have limited research supporting their efficacy. This study mainly compared the effect of Zn-seed treatment rate in combination with other low-use-rate Zn-fertilization methods to the standard of 11 kg Zn ha-1 as ZnSO4 on rice early-season canopy cover, tissue-Zn concentration, and grain yield. A secondary objective evaluated an alternative method (to seed treatment with ZnO) of enhancing seed-Zn concentration using post-heading foliar-Zn application on seedling tissue-Zn concentration and grain yield. For the main objective, rice seed was treated with 0 or 3.3 g Zn kg-1 using ZnO. The treated rice seed was planted and received the following Zn treatments in the field: i) no-Zn, ii) granular ZnSO4 applied at 11 kg Zn ha-1 (GRAN), iii) 1.68 kg Zn ha-1 as MicroEssentials (MESZ), iv) 1.1 kg Zn ha-1 as foliar-applied Zn-EDTA (EDTA), and v/vi) 0.56 and 1.12 kg Zn ha-1 of WolfTrax Zn-DDP (DDP). For the second objective, in 2017, rice seed was biofortified by applying 0, 1, 2, or 3 applications of 1.75 kg Zn ha-1 as ZnSO4 solution after 100% panicle emergence. In 2018, a greenhouse experiment evaluated non-fortified rice seed treated with ZnO compared to Zn-biofortified seed without a ZnO coating. In the field, each level of biofortified rice was planted with and without a ZnO-seed treatment. For the first objective, canopy coverage at two site-years was significantly affected by Zn-fertilization method or the significant Zn-seed treatment rate and Zn-fertilization method interaction. Rice fertilized with MESZ had the greatest canopy coverage at these sites. Rice receiving GRAN, increased seedling-Zn concentration by at least 4.3 mg Zn kg-1 above rice not receiving Zn. A ZnO-seed treatment increased seedling-Zn concentration above rice that did not receive a ZnO-seed treatment. In general, low-use-rate Zn fertilizers provide minimal Zn nutrition for rice seedlings, and should be avoided on fields where Zn deficiencies are probable. For the second objective investigating biofortification of rice seed with Zn, the ZnO-seed treatment provided greater Zn nutrition for seedling rice compared to biofortified rice grains indicating that ZnO-seed treatments are more advantageous than Zn biofortification for early-season Zn nutrition of seedling rice.

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