|Mccarty, M -|
|Tacker, P -|
|Stevens, W -|
Submitted to: Rice Technical Working Group Meeting Proceedings
Publication Type: Abstract Only
Publication Acceptance Date: December 1, 2009
Publication Date: December 1, 2010
Citation: Vories, E.D., Mccarty, M., Tacker, P., Stevens, W. 2010. Spatial Variability of Yield for Sprinkler Irrigated Rice. Rice Technical Working Group Meeting Proceedings. CD-ROM. Technical Abstract: Most of the rice in the Mid-South is produced in a flooded culture for much of the growing season and generally requires more irrigation water than other crops produced in the region. By 1915 the alluvial aquifer, the principal water source for agriculture in eastern Arkansas and surrounding areas, was already being tapped at a rate that exceeded its ability to recharge. The problem was exacerbated as Arkansas rice production increased to > 650,000 ha and rice production also increased in neighboring states of Mississippi, Louisiana, and Missouri, with more than half of the US rice crop currently produced in the Mid-South. Different production systems have been investigated to reduce the water requirement for Mid-South rice production, including furrow irrigation, delayed flooding, intermittent flooding, and multiple inlet rice irrigation with varying levels of success. Rice production under center pivot irrigation was investigated in the 1980's, but was not widely adopted. However, in 2009, Zimmatic (Lindsay Corp., Omaha, Nebr.; mention of trade names or commercial products is solely for the purpose of providing specific information and does not imply recommendation or endorsement by the US Department of Agriculture) and Valley (Valmont Irrigation, Valley, Nebr.) worked with Mid-South farmers and researchers to revisit the potential for center pivot rice production. Among the questions being addressed: can rice yields comparable to flooded production be obtained with sprinkler irrigation; can center pivot rice be produced economically; can water be saved relative to flooded production; and will highly variable Mid-South soils negatively impact the spatial distribution of yield with sprinkler irrigation? When rice is produced in a flooded culture, water is uniformly available across the field. With sprinklers, however, the distribution uniformity of the irrigation system impacts how much water is delivered to an area, while soil variability leads to site-specific differences in how much of that water is available to the plants. Center pivot systems typically have high application efficiencies, with published values as high as 90%. However, the combination of alluvial, wind, and seismic activity over the years has resulted in highly variable soils in the Mid-South. It is common to have soil mapping units ranging from sand to clay within the same field. One such field located near Osceola, Ark., is managed by McCarty Farms. The Mississippi County Soil Survey reports that the approximately 60 ha, center-pivot-irrigated field contains large areas mapped as Convent fine sandy loam, Steele loamy sand, Commerce silt loam, Tunica silty clay, and Sharkey-Steele complex (approximately 70% Sharkey silty clay or silty clay loam and 30% Steele loamy sand extruded during the New Madrid earthquakes of the early 19th century). Smaller areas were mapped as Jeanerette silt loam and Sharkey-Crevasse complex (approximately 50% Sharkey, 30% Crevasse loamy sand also extruded during the New Madrid earthquakes, and 20% Steele and Tunica soils). Such a field should be a perfect place to investigate the spatial distribution of yield when rice is produced with center pivot irrigation. In 2009, working with local and national Zimmatic representatives, McCarty Farms planted the southern half of the field, approximately 30 ha, with the hybrid 'Clearfield XL745' (RiceTec, Inc., Alvin, Tex.). Water was applied with the pivot to germinate the seed and incorporate herbicide. During the typical flood period 18 mm applications were made approximately every other day in the absence of rain for a total of 464 mm of water applied to the crop. A published estimate of the pumping requirement for rice in Arkansas is 760 mm, based on several years of on-farm observations. However, the large areas of sandy soils in the field (primarily Convent and Steele) suggest that more water would be required to maintain a flood in this field than the typical rice field. Yield monitor data from one of the two JD 9770 STS combines (Deere & Company, Moline, Ill.) used in the harvest was analyzed to investigate spatial yield variability. Yield data were "cleaned" with the USDA-ARS Yield Editor program (v. 1.02) to remove erroneous data points and the average yield for the combine was assumed to be the field average dry yield of 9.7 Mg ha-1 (192 bushels acre-1). Yield from the two largest contiguous blocks (4.8 and 3.8 ha) was analyzed for uniformity. The larger block contained areas mapped as Tunica (38% of the block), Steele (51%), and Sharkey-Steele complex (11%). The average yield for the block was 9.7 Mg ha-1, and the yields from the individual mapping units ranged from 9.6 Mg ha-1 (Tunica) to 9.9 Mg ha-1 (Sharkey-Steele complex). Similarly, the smaller block contained areas mapped as Steele (30%), Commerce (67%), and Convent (2%). The average yield for the block was 10.2 Mg ha-1, and the yields from the individual mapping units ranged from 10.2 Mg ha-1 (Commerce) to 10.6 Mg ha-1 (Convent). Furthermore, interpolated yield maps did not indicate any patterns that corresponded to the mapping units. Although additional work remains, the preliminary answers to the above questions are: yields comparable to flooded rice were obtained with sprinkler irrigation; rice was produced economically (not addressed in this report); water was saved relative to flooded production; and highly variable Mid-South soils did not appear to impact the spatial distribution of yield with sprinkler irrigation. Additional studies are planned.