Submitted to: Weed Science Society of America Meeting Abstracts
Publication Type: Abstract Only
Publication Acceptance Date: 9/15/2003
Publication Date: 1/26/2004
Citation: Smith, M.C., Massey, J.H., Scherder, E.F., Talbert, R.E., Ottis, B.V., Vories, E.D., Weaver, M.A., Zablotowicz, R.M., Locke, M.A. 2004. Effect of intermittent irrigation on rice agronomics, environmental conservation and pest management. Southern Weed Science Society of America Abstracts. 57:60.
Technical Abstract: The alluvial aquifer in the Grand Prairie region of Arkansas will not support irrigated agriculture by 2015 due to overdrafts attributed to intensive rice cultivation. Additionally, the depletion of Arkansas' alluvial aquifer has caught the attention of environmental regulators in Mississippi. The alluvial aquifer within the Mississippi Delta's rice and aquaculture region has declined 11 in per year since 1993. To avoid impending regulation, rice producers in Mississippi must demonstrate that alternative cropping systems can slow or reverse groundwater depletion. Rice requires ca. 20 A-in water per season. Water inputs include both natural rainfall and irrigation. Irrigating continuously flooded rice with levee-gate distribution consumes 30 to 40 A-inches of water. With levee-gate flood distribution, each paddy must be filled to overflowing to deliver water to a successive down-slope paddy. However, with multiple-inlet irrigation, each paddy is flooded simultaneously, which can reduce over-filling and excessive runoff. With continuously flooded rice, once the flood is established it is maintained at near maximum capacity. Thus, the rice paddies are unable to capture water from the 10 A-in of rainfall during the months of June, July and August. In intermittently flooded rice, flood depth fluctuates between fully flooded and half of the paddy 'showing' exposed soil. This decreases the average flood depth, captures rainfall, reduces tail-water runoff and decreases irrigation inputs. A production-scale project was begun in Mississippi in 2003 to extend water-saving research initiated by the University of Arkansas into the Mississippi rice-growing region. This project compared water consumption, agronomics, and pest pressure between rice grown in continuously flooded and intermittently flooded water management systems. The project was located in adjacent production fields in Coahoma County, Mississippi. The soil was a Sharkey silty clay loam with 25% clay, pH 6.7, 1.8% organic matter and 0.1 % uniform slope. The continuously flooded treatment used multiple-inlet distribution delivering 17 gal min-1 A-1 to a 72.2 A field. The intermittently flooded treatment also used multiple-inlet distribution delivering 15 gal min-1 A-1 to a 32.2 A field. Both fields followed a two-year soybean rotation. Sixty-eight lb A-l Cocodrie rice was planted on 21 April 2003. Weed control included Command + Bolero, delayed-PRE followed by âFlexstar, preflood, âRegiment, and postflood. All herbicides were applied at the manufacturer recommended rates. Fertility included 100 lb A-1 N preflood followed by 50 lb A-1 N midseason applied as urea. Flood was established on 30 May 2003 and terminated approximately 85 days later. Initially, the producer was uncomfortable allowing the flood in the intermittently flooded field to subside to the target depth. As a result, both the continuously and intermittently flooded rice systems used approximately 0.34 A-in day-1 during the first 30 days after flood initiation. After the initial reluctance to follow an intermittent flooding schedule was overcome, the daily irrigation rate was 0.16 A-in day-1 in the intermittently flooded system compared to 0.35 A-in day-1 in the continuously flooded system. After 85 days of flooding, the continuously flooded system consumed 28 A-in of water compared to 18 A-in in the intermittently flooded system. Insect, disease and weed infestations did not differ between the two flooding systems. Intermittent flooding did not affect flag-leaf nutrient concentrations when compared rice in the continuously flooded adjacent field. Rice grown in the intermittently flooded system yielded 189 bu A-1 compared to 183 bu A-1 from rice in the continuously flooded system. Intermittent flooding with multiple-inlet irrigation appears to be a feasible water-saving irrigation practice for rice producers in