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United States Department of Agriculture

Agricultural Research Service

Research Project: IMPROVING IRRIGATION MANAGEMENT FOR HUMID AND SUB-HUMID CLIMATES

Location: Cropping Systems and Water Quality Research

Title: Initiating and terminating irrigation for the season

Authors
item Vories, Earl
item Barnes, Edward -

Submitted to: Cotton Irrigation Management for Humid Region
Publication Type: Book / Chapter
Publication Acceptance Date: July 13, 2012
Publication Date: September 17, 2012
Citation: Vories, E.D., Barnes, E.M. 2012. Initiating and terminating irrigation for the season. In: Perry, C., Barnes, E., editors. Cotton Irrigation Management for Humid Region. Cary, North Carolina: Cotton Incorporated. p. 12-13.

Interpretive Summary: In the Mid-South and Southeast there is often residual soil moisture to get the crop started and producers generally prefer to delay irrigation as long as possible so all of the early season field operations can be completed, particularly in furrow irrigated fields. However, poor moisture conditions near the time of emergence can result in thin and spotty stands that require replanting or create management problems for the rest of the season. In the first 30 days after emergence, cotton water demands are low and the of the crop is the least water-sensitive; however, the crop is much more sensitive to water stress after this point. Studies in the Mid-South showed a consistent trend for lower yield and lower net revenues for each delay in the first irrigation; therefore, following irrigation recommendations based on field sensors or scheduling programs is important. The perennial nature of cotton makes it difficult to make end-of-season decisions about when to stop applying water and for fields north of 34 degrees N latitude it was determined that an irrigation applied after 18 days past NAWF5 would not increase yield enough to be profitable. These findings will reduce costs for cotton producers and everyone will benefit from the savings in irrigation water.

Technical Abstract: In the arid west, the question about when to start irrigating was never asked because cotton did not start to grow until water was applied. In the Mid-South and Southeast, however, there is often residual soil moisture to get the crop started. In general, producers prefer to delay irrigation as long as possible so all of the early season field operations can be completed, particularly in furrow irrigated fields. Poor moisture conditions near the time of emergence can result in thin and spotty stands that require replanting or create management problems for the rest of the season. Therefore, if soil moisture limitations threaten a good stand, irrigate. Water use is very low at this point in the crop’s development so a large volume of water is not needed, which may make application with a furrow or flood system impractical. In the first 30 days after emergence, cotton water demands are low and this is one of the least water-sensitive time periods for the crop; however, the crop is much more sensitive to water stress after this point. Studies in the Mid-South showed a consistent trend for lower yield for each delay in the first irrigation and when the costs of irrigation were considered, delaying irrigation also led to lower net revenues. Therefore, following irrigation recommendations based on field sensors or scheduling programs is important. The perennial nature of cotton makes it difficult to make end-of-season decisions about when to stop applying water. A study was carried on in the Mid-South to see if the COTMAN approach could be applied to irrigation termination and a clear relationship was observed between time after five nodes above white flower (NAWF5) and time of the last irrigation for fields north of 34 degrees N latitude where it was determined that an irrigation applied after 18 days past NAWF5 would not increase yield enough to be profitable.

Last Modified: 9/1/2014
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