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ARS Home » Southeast Area » Jonesboro, Arkansas » Delta Water Management Research » Research » Publications at this Location » Publication #304559
Title: Final irrigation timing 2013 in Northeast Arkansas cotton

Author
item TEAGUE, TINA - Arkansas State University
item Reba, Michele

Submitted to: Arkansas Agricultural Experiment Station Research Series
Publication Type: Experiment Station
Publication Acceptance Date: 4/8/2014
Publication Date: 8/1/2014
Citation: Teague, T.G., Reba, M.L. 2014. Final irrigation timing 2013 in Northeast Arkansas cotton. IN: Arkansas Agricultural Experiment Station Research Series. 618:40-46.

Interpretive Summary: Research results reported by Vories et al 2011 suggest evaluating the crop for timing the final irrigation at 350 after cutout. We had similar findings in 2013. Extending the irrigation season with an additional irrigation on 21 August at seasonal cutout + 366 DD60s had no effect on yield. Based on Watermark sensors, soil moisture appeared sufficient at the crop stage appropriate for termination. Soil moisture dropped below those values prior to harvest. It is unknown if additional irrigations would have impacted yield, although in previous research with multiple extended end-dates for final irrigation at the same production farm, this has not been shown. Soil moisture sensors should inform irrigation managers on not only when to schedule irrigations but also the effectiveness of their irrigations. The Watermark sensors failed to detect irrigation events in sandy loam soils. These data suggest a lack of capillary rise in the raised beds. The apparent lack of plant-available water resulted due to reduced infiltration and greater runoff. Expanded research is needed to improve irrigation water availability to plants and also on placement of sensors to detect plant available water. Expanded and efficient use of soil sensor information ultimately should provide irrigation managers with greater confidence in scheduling irrigation as well as using plant-based irrigation termination timing. This will benefit Arkansas’s cotton growers by reducing production costs without sacrificing yield or fiber quality.

Technical Abstract: The perennial nature of the cotton plant often complicates end-of-season decision-making. The question of when to quit has been the focus of a long standing research that includes work on termination of insect control, irrigation and for defoliation A key component to termination timing is identification of the final population of bolls that effectively contribute to yield. The date of cutout is the flowering date of that last economically significant boll population. All late season management decisions are then based on maturity of those bolls determined by accumulated heat units. Heat units, often referred to as Growing Degree Days, are calculated using the base temperature for cotton, 60 °F, expressed as DD60s. Uncertainty by decision-makers on irrigation termination timing based simply on plant maturity and accumulated DD60s arises when managers lack confidence that their crop has access to adequate available water to complete maturity of the last effective bolls. Soil moisture sensors may provide that needed evidence so that managers may be confident in the decision to stop irrigating. In this 2013 on-farm study, we compared cotton yields with termination timing based on seasonal cutout compared to an extended irrigation. Soil moisture sensors were used to reference soil water availability in the furrow-irrigated field. We hypothesized that if maturity of the last effective bolls indicate that the crop has reached the irrigation termination threshold, and soil moisture levels show adequate soil moisture availability, further irrigation would be unnecessary. Research results reported by Vories et al 2011 suggest evaluating the crop for timing the final irrigation at 350 after cutout. We had similar findings in 2013. Extending the irrigation season with an additional irrigation on 21 August at seasonal cutout + 366 DD60s had no effect on yield. Based on Watermark sensors, soil moisture appeared sufficient at the crop stage appropriate for termination. Soil moisture dropped below those values prior to harvest. It is unknown if additional irrigations would have impacted yield, although in previous research with multiple extended end-dates for final irrigation at the same production farm, this has not been shown.