Date of Graduation

5-2021

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

Gbur, Edward E. Jr.

Second Committee Member

Hardke, Jarrod T.

Third Committee Member

Roberts, Trenton L.

Fourth Committee Member

Golden, Bobby R.

Keywords

Clay soils; Early season growth; Grain yield; Preflood nitrogen; Rice; Starter nitrogen

Abstract

Seedling rice (Oryza sativa L.) grown on clayey-textured soils generally develops slowly as compared to loamy-textured soils. Our research examined the effects of starter-N source and preflood-N rates on canopy closure, total aboveground N uptake, and grain yield of rice grown on clayey-textured soils. Eleven field trials were established in Arkansas and Mississippi including five trials with a hybrid cultivar and six trials using a pure-line cultivar. Starter-N sources included no starter-N (NONE), ammonium sulfate (AMS), diammonium phosphate (DAP), and urea (UREA) applied at 24 kg N ha-1 at the rice 2-leaf stage and five preflood-N rates ranging from 0-224 kg N ha-1 at the 5-leaf stage. Canopy cover was measured weekly on trials conducted in Arkansas for 5 wk after starter-N application. Rice that received no starter-N produced less canopy coverage than rice receiving starter-N as AMS, DAP, and UREA and AMS, DAP, and UREA produced no differences in canopy coverage. Aboveground total-N uptake was affected only by the preflood-N rate for each site-year with maximum N uptake ranging from 139-196 kg N ha-1. The preflood urea-N recovery efficiency for rice receiving no starter-N ranged from 54-78% among trials. For the Arkansas trials, rice that received the three starter-N sources produced 3.4-5.0% greater relative yield compared to rice receiving no starter. Relative yield for the Mississippi trials was not affected by starter-N source. Results show that starter-N can benefit early season growth and grain yield of rice grown on clayey soils but the benefits are not consistent.

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