|Tacker, P - UNIVERSITY OF ARKANSAS|
|Hogan, R - UNIVERSITY OF ARKANSAS|
|Smith, L - UNIVERSITY OF ARKANSAS|
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: December 2, 2005
Publication Date: December 20, 2006
Citation: Tacker, P.L., Vories, E.D., Hogan, R., Smith, L.W. 2006. Improved water management with multiple inlet rice irrigation [abstract]. Proc. 31st Rice Technical Working Group Meeting Proceedings. p.137 (CD-ROM) Technical Abstract: Rice production is an important component of Arkansas' and other southern states' agriculture. In 2003, rice accounted for over $1.2 billion in total cash receipts, almost 10 percent of the state totals for all commodities for both Arkansas (9.7 %) and Louisiana (8.3 %). When combined with the rice processing, agricultural equipment, and other businesses supporting rice production, it is apparent that rice is important to the overall economy, and not just in the rice-producing states. While rice is produced in some parts of the world in an upland, rain fed culture, almost all US-produced rice is grown in a flooded culture. In the dry-seeding system the crop is usually flooded at approximately the V-4 growth stage and, unless a disease or fertility problem requires the field to be dried, a continuous flood is maintained until after heading. Reported values for the amount of irrigation water applied to rice in Arkansas range from 610 to 1220 mm. Even at the 610 mm amount, rice production in Arkansas requires an average of at least 3.8 million m3 of irrigation water per year. The large amount of water applied to rice has resulted in two problems. The energy costs associated with pumping make up a significant portion of the rice production budget, especially with the significant increase in diesel fuel prices. In addition, groundwater shortages are being observed in parts of Arkansas and other rice-producing areas and similar problems with surface water sources have been encountered. For both reasons, reducing the water requirements for rice has been a goal of farmers and researchers for many years. Multiple Inlet Rice Irrigation (MIRI) is an alternative method for applying flood water that has the potential to help address these problems. The research objective was to investigate whether MIRI would reduce the water being pumped for rice production, without reducing yields, when used on production-scale fields by the regular farm employees. In order to study water requirements for rice on a production scale, on-farm water use studies were conducted during the 1999 through 2002 growing seasons. The studies consisted of paired fields located close together, with the same cultivar, soil type, planting date and management practices. One of the fields was randomly assigned as a conventionally flooded field (CONV) and the other was assigned as MIRI. Propeller-type flow meters were installed in both fields to measure the amount of water pumped, and the farmer provided yield data for the fields. During the four-year study period, data for comparisons were collected from 14 pairs of fields ranging in size from 12.5 to 32.4 ha. The farms represented the northern, central, and southern portions of the rice-growing region in Arkansas, and the range of soil types used for rice production. The MIRI method required an average of 24 % less irrigation water than conventional flooding, with 930 and 703 mm for CONV and MIRI, respectively. In addition, the MIRI field used less water for each of the fourteen farms, ranging from 10 % less to 42 % less. Rice grain yields were 3.4 % greater for MIRI, with 7.41 and 7.66 Mg/ha for CONV and MIRI, respectively. Differences ranged from 13 % greater for MIRI to 3 % greater for CONV. Since both the irrigation water applied and yield favored MIRI, the irrigation water use efficiency (WUE) (i.e., yield produced per unit of irrigation water applied) favored MIRI. In fact, an average 36 % WUE increase was associated with MIRI, with 8.74 and 11.89 kg/ha-mm for CONV and MIRI, respectively. Differences ranged from 15 % greater to 81 % greater for MIRI. Two possible factors affecting yield were the "cold water effect" and nitrogen efficiency. The cold water effect from groundwater and conventional flooding refers to the area around the well or riser that is typically later maturing and lower yielding than the rest of the field. This is a function of water temperature effect on the plants and the calcium precipitate that occurs from the water being exposed to the air and warmed. Introducing the water at several points in the field appears to reduce the cold water effect. The recommendation for minimizing nitrogen losses is to apply the initial flood within five days of the fertilizer application. This time frame is often exceeded with conventional flooding; however, most cooperators report less time being required to cover the field with water when using MIRI. In addition to the water savings and potential yield increase, most producers indicate that MIRI results in a reduction in labor of approximately 25%. A notable quote from one producer concerning MIRI is, “It makes it possible for me to manage the water instead of the water managing me”.