| Popis: |
While continuous-flood irrigation, the most common method for U.S. rice production, can have a fairly high irrigation application efficiency, factors such as soil variability and the size of most Mid-South farming operations often combine to reduce the efficiency. Center pivot irrigation is a way to reduce irrigation water use in some cases and allow rice in the crop rotation in other situations when flooding is not practical. Rice was produced at the University of Missouri Fisher Delta Research Center Marsh Farm at Portageville in 2009 and 2010 and irrigated every other day with a 150-m-long center pivot irrigation system. An experimental crop coefficient function was developed and included in a beta version of the Arkansas Irrigation Scheduler (AIS). It was used with daily short grass reference evapotranspiration (ETo) calculated from weather data collected on site to estimate the daily soil water deficit (SWD). Weather conditions were warmer and much drier in 2010 and ETo was higher each month. In 2009, there were totals of 34 days with irrigation and 414 mm of water applied. In 2010, there were totals of 45 days with irrigation and 503 mm of irrigation water applied. In 2009, the cultivar Templeton had the highest observed grain yield (8.31 Mg ha-1) and irrigation water use efficiency (IWUE; 2.0 kg m-3). In 2010, the cultivar Francis had the highest observed grain yield (8.2 Mg ha-1) and IWUE (1.6 kg m-3). In addition to the higher temperatures in 2010, yields were probably impacted by the fact that rice was produced in the field the two previous years. Future research will use the beta version of the AIS to schedule irrigations, which should indicate whether the crop coefficient is adequate and allow producers a system for scheduling center pivot irrigation on rice. |
