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Title: RICE RESPONSES TO CHANGES IN FLOODWATER AND N TIMING IN SOUTHERN USA

Author
item Grigg, Brandon
item BEYROUTY, C A - UNIVERSITY OF ARKANSAS
item NORMAN, R J - UNIVERSITY OF ARKANSAS
item GBUR, E E - UNIVERSITY OF ARKANSAS
item HANSON, M G - UNIVERSITY OF ARKANSAS
item WELLS, B R - UNIVERSITY OF ARKANSAS

Submitted to: Field Crops Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/29/1999
Publication Date: N/A
Citation: N/A

Interpretive Summary: Rice producers in the southern U.S. can benefit from improved flood scheduling that allows for more flexible cultural and agrochemical management, increased water conservation, and reduced water pumping costs. We determined the response of multiple rice varieties to delayed flood application or early flood removal and to altered nitrogen fertilizer scheduling to complement these changes in water management. We also evaluated season-long flush irrigation in contrast to flooded management. However, this practice results in plant growth and grain yield and appears incompatible with the production of modern rice varieties optimized for flooded production. Changes in flood scheduling did not affect head-rice yield. This indicates that rice producers can delay flood application by approximately 14 days beyond the typical application at the 4 to 5 leaf stage, and can remove flood waters earlier than normal, 14 days after heading. Altered nitrogen scheduling, specifically as a single application rather than the normal split application, increased plant uptake of nitrogen, but did not increase grain yield. These results suggest that rice producers in the southern U.S. can decrease the duration of floodwater application without sacrificing grain yield or quality. Future research is needed to determine changes in water usage and pumping costs resulting from delayed flooding and early flood removal.

Technical Abstract: Delayed application and or early draining of floodwater to lowland irrigated rice (Oryza sativa L.) should allow producers in the southern U.S.A. greater flexibility in chemical and cultural crop management, and reduce water use and pumping costs. Two field studies were conducted to evaluate whole plant response of Tebonnet and shoot growth and yield responses of Tebonnet, Alan, and Texmont to reduced flood duration and altered N management. Depending upon the study, treatments consisted of recommended flood application (normal flood) and delayed flood application (delayed flood) in combination with recommended or early draining of the floodwater, as well as full season flush irrigation. Nitrogen was either applied once at the 4 to 5 leaf stage or as a normal or earlier than recommended- three-way split. Flush irrigation significantly reduced shoot and root growth and yield of rice as compared to normal flood. Compared to normal flooded rice, plant height and shoot dry weights were significantly lower for delayed flooded rice, although no significant differences in root length densities or grain and head rice yields were observed. N uptake was greatest with a single application of N as compared to a three way split application, however, this did not affect yield. Likewise, yields were not affected by early draining of floodwater. These data suggest that the current duration of floodwater application in rice production in the southern U.S. may be reduced without sacrificing grain yield or quality.