Submitted to: Crop Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/5/2012
Publication Date: 7/1/2012
Citation: Conaty, W., Burke, J.J., Mahan, J.R., Sutton, B., Neilsen, J. 2012. The Optimum Plant Temperature for Cotton Growth and Metabolism to Schedule Irrigation. Crop Science. 52(4): 1828-1836. Interpretive Summary: The BIOTIC irrigation protocol previously developed by the UADS/ARS uses an estimate of the optimum temperature of a plant as the basis of irrigation scheduling. Optimal temperatures have been determined for cotton varieties commonly grown in the USA, Recent interest in the use of the BIOTIC method in Australian cotton production resulted in the need to determine the optimal temperature for a common Australian variety. The optimum temperature was determined by three methods in both greenhouse and field experiments and was found to be very in full agreement with that of US varieties. This information is currently being used in further studies on the implementation of BIOTIC in Australia.
Technical Abstract: A plant based thermal optimum approach to irrigation scheduling provides potential benefits to irrigation scheduling in that water applications are scheduled on the basis of plant water deficits. It is tempting for producers to employ this method, particularly in the wake of technologies, such as infrared thermometers, becoming increasingly more cost effective and reliable. Such irrigation systems require a defined thermal optimum for the crop and while such optimum values have been identified for cotton varieties in the USA, there is no information of this type for varieties common in Australian production. This paper outlines a three-fold approach to determining the optimum temperature (Topt) of the commercial Australian cotton cultivar Sicot 70BRF, in an Australian production system. It combines the use of a laboratory-based fluorescence assay, field-based carbon assimilation (A) and stomatal conductance (g) rates, and seasonal canopy temperature (Tc)-yield relations. The fluorescence assay showed a Topt between 28 and 30 °C, whilst leaf gas exchange rates showed a peaked at leaf temperature (Tl) of 29 °C. Seasonal Tc - yield relations peak at 26 °C, with yield reductions observed when Tc > 28 °C. We conclude the Topt of the Australian upland cotton cultivar Sicot 70BRF to be 28 ± 2 °C. This Topt will provide valuable information for use in thermal optimum irrigation scheduling systems.