Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: September 19, 2011
Publication Date: August 1, 2012
Citation: Evett, S.R., Baumhardt, R.L., Howell, T.A., Ibragimov, N.M., Hunsaker, D.J. 2012. Cotton. In: Steduto, P., Hsiao, T.C., Fereres, E., Raes, D., editors. Crop Yield Response to Water. 2nd Edition. Irrigation and Drainage Paper No. 66. p. 154-161. United Nations Food and Agriculture Organization. Interpretive Summary: Cotton is an important cash crop in the United States, which is the third ranked producer in the world. Scientists at the USDA-ARS Conservation & Production Research Laboratory, Bushland, Texas, collaborated with scientists from Arizona and Central Asia to write this chapter describing cotton growth and development, water use and productivity, response to stresses, irrigation practices, and yield. The chapter presents an example application of a cotton growth, yield, and water use computer model. The model is aimed at providing producers with a reliable way to explore different cotton management alternatives before committing to growing a crop in the field. This AquaCrop model was a collaborative project involving the ARS scientists and led by the United Nations Food and Agriculture Organization, which will publish the chapter. The model was shown to estimate crop yields well under both fully irrigated and deficit-irrigated conditions, a fact that is important to producers in the water-short Southern High Plains, Arizona, California, and New Mexico. Deficit irrigated cotton yields were 95% of those from the fully irrigated crop, while irrigation was only 43% of the full irrigation amount, indicating a savings of 10 inches of water with very little loss of yield. The savings in pumping costs alone more than make up for the reduced yield in this scenario.
Technical Abstract: Cotton is a woody, perennial, indeterminate plant with the C3 photosynthesis pathway, that is grown in warm and some temperate climates for fiber, but also for its seed from which oil and protein are important products. Of the four cultivated forms of cotton, the dominant species in production is Gossypium hirsutum, also known as Upland cotton, which is managed as an annual. Since 1980, production has increased 60%, while the area harvested worldwide remained quite stable. In 2007, world production was 24.2 million Mg seed lint. Cotton is grown around the world from the tropics to latitudes as great as 42 deg (Uzbekistan), with major producers being China (31%), India (18%), the USA (17%), Pakistan (8%), Brazil (6%), Uzbekistan (5%), and Turkey (5%). This chapter describes cotton growth and development, water use and productivity, response to stresses, irrigation practices, and yield. It then presents sample applications of the AquaCrop model of crop growth, yield, and water use. The examples are for a well-watered crop and a deficit-irrigated crop. Deficit-irrigated cotton seed-lint yields tended to be approximately 95% of yields from fully irrigated cotton. Simulated yields were in the range of 3.3 to 3.6 Mg ha**-1, which is equivalent to 1.3 to 1.4 Mg ha**-1 of lint and comparable to values reported in the region 17. The water use efficiency of deficit irrigated cotton was approximately 10% greater than that of fully irrigated cotton (both in the range of 0.49 to 0.54 kg seed/lint m**-3, or 0.19 to 0.21 kg lint m**-3). Crop evapotranspiration was approximately 15% greater for fully irrigated cotton than for deficit irrigated cotton, both in the range of 625 to 720 mm, which matched well with observed values in several regions. However, deficit irrigation was 240 mm, only about 43% of the full irrigation amount, indicating that soil water was mined during the cotton season.