Date of Graduation

5-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Crop, Soil & Environmental Sciences (PhD)

Degree Level

Graduate

Department

Crop, Soil & Environmental Sciences

Advisor/Mentor

Hardke, Jarrod T.

Committee Member

Roberts, Trenton L.

Second Committee Member

Daniels, Michael B.

Third Committee Member

Carey, Frank

Keywords

Alternate wetting and drying; Furrow-irrigated; Irrigation; Nitrogen; Rice; Row rice

Abstract

As water resources gain value across the Mid-South, alternative irrigation strategies of rice (Oryza sativa L.) have garnered increasing attention. In 2015, an estimated 1.7% of Arkansas rice hectarage used alternate wetting and drying (AWD) irrigation and 0.9% used furrow irrigation. As of 2020, 2.5% used AWD and 16.9% used furrow irrigation, the latter accounting for near 99,000 ha in Arkansas. Little information exists in the scientific literature in relation to management of rice grown in the Mid-South without a conventional flood. This fact coupled with the rapid adoption rate, especially for furrow-irrigated rice (FIR), during the last five years prompted the need for additional scientific information. Studies were initiated from 2018 through 2020 to examine several management differences under alternative irrigation strategies, including irrigation timing, fertilizer-nitrogen (N) management, and nutrient uptake surveys. Large block trials were conducted in 2018 and 2019 to assess the proper irrigation timing for AWD and FIR at a total of four site-years per irrigation method. Small-plot trials were conducted in the top (aerobic) and bottom (generally flooded, anaerobic) of FIR fields from 2018 to 2020 at thirteen sites to determine the optimum N management program for FIR on clayey and silt loam soils. From these small-plot trials, aboveground biomass samples were taken at R3 (50% heading) to analyze the nutrient uptake including N, phosphorus (P), potassium (K), zinc (Zn), and eight other plant-essential nutrients. Results indicate that AWD and FIR can be allowed to dry to at least -45 kPa in the upper third of the field at depth of 10 cm prior to each irrigation event. The optimal N program for FIR on clayey soils was a three-way split application, which included an additional 52 kg N ha-1 over the recommended season total N rate for flooded rice production, but further economic analysis is certainly needed. While this program also maximized rice grain and milling yield on a silt loam soil, it appears that the extra 52 kg N ha-1 may not be needed and that more management options may be possible to optimize FIR production on a silt loam soil. However, it appears that there is no need to manage the top and bottom of the field separately in terms of N management. Nutrient uptake surveys from sites on both clayey and silt loam soil textures suggest that P and K uptake are much less at the top of the field, where aerobic conditions generally exist throughout the season. Thus, it may be necessary to focus on P and K management in FIR in the future and amended management recommendations may be advised. Through the studies conducted as a part of this project, it has been shown that AWD and FIR production are viable methods for growing rice in the Mid-South. The management aspects examined in the current studies should allow rice producers considering AWD, and especially FIR, to maximize rice grain yield and milling yield while minimizing the potential negative environmental impact associated with the transition to these alternative methods of rice irrigation.

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