Submitted to: Applied Engineering in Agriculture
Publication Type: Peer reviewed journal
Publication Acceptance Date: 5/16/2003
Publication Date: 10/1/2003
Citation: Enciso, J., Unruh, B., Colaizzi, P.D., Multer, W. 2003. Cotton response to subsurface drip irrigation frequency under deficit irrigation. Applied Engineering in Agriculture. 19:555-558. Interpretive Summary: West Texas is an arid but very productive region for cotton; however, irrigation is required and almost all of this is supplied by groundwater. In order to conserve groundwater, many farmers in this and other regions have converted from traditional flood to subsurface drip irrigation. In subsurface drip irrigation, water is trickled to plant roots through buried plastic tubing (called 'drip tape') with small holes (called 'emitters'). Besides conserving water, subsurface drip may also enhance crop yields and quality, especially on poor soils. There is uncertainty, however, on how often cotton should be irrigated using subsurface drip. For example, using a given amount of water, is it better to irrigate a little everyday or a lot once a week? Past research in other locations showed that in some cases, irrigating more often but with less amounts of water can improve yields of cotton and other crops, but this requires greater management and possibly the added expense of automating the irrigation system. To answer this question, we worked with a farmer from St. Lawrence during the 1999 and 2000 cotton seasons. Eight plots (approximately 1.4 acres each) were set up for subsurface drip irrigation on good quality soil. Half the plots in 1999 were irrigated every 16 days (low frequency) and the other half every 4 days (high frequency), but all plots received the same amount of water. In 2000, we shortened the irrigation intervals to 8 and 2 days, respectively, and again all plots received the same amount of water. In both years, there were no significant differences in cotton yield, quality, or gross returns; however, the high frequency plots had slightly better yield and gross returns, but cotton quality was slightly better in the low frequency plots. We conclude that for subsurface drip irrigated cotton in West Texas, there is no advantage to high frequency irrigation provided soil quality is good (i.e., able to store sufficient water). Consequently, farmers should have more flexibility in managing field operations and depending on the size of the farm, may avoid the added expense of automating their irrigation systems. Nonetheless, there may be advantages to high frequency irrigation if soil quality is poor (i.e., non-uniform and/or less capable of storing water) or for crops with shallow roots such as vegetables.
Technical Abstract: Cotton lint yield and quality were investigated for different irrigation frequencies using subsurface drip irrigation system (SDI) under limited water conditions (1.7 mm day-1) in the St. Lawrence region of West Texas, U.S.A. Two frequency intervals were studied during two years; these were 4 days and 16 days in 1999 and 2 days and 8 days in 2000. Each treatment was replicated four times, and the total amount of water applied each year was the same. The soil is a silty clay loam soil underlain by caliche just below 90 cm from the surface. In both years, there were no significant differences between frequency treatments in lint yield, micronaire, fiber length, fiber strength, uniformity, or gross returns. Using the loan values as an indicator of lint quality, cotton loan values were highly significant in 1999, but were not different in 2000. With no major advantage in increasing irrigation frequency using SDI under deficit conditions, these results may have an impact on the agronomic practices of the region where water is very limited. Low frequency irrigation may allow farmers to have more flexibility in managing their irrigation systems and avoid the additional expense of automating a microirrigation system.