Use of irrigation has been increasing across the humid areas of the Cotton Belt for the last 20 years. While there is a large collection of information for irrigation management related to cotton in arid regions, information specific to management under humid conditions is not as well developed. Therefore, the objective of this publication is to provide producers with an overview of the technologies available to schedule irrigation and key concepts related to water management for cotton grown in areas where rainfall provides a significant amount of the water requirements in most years.
This document is divided into nine sections that address a variety of topics including: the benefits of irrigation and why water management is important; cotton water requirements in humid areas; growth stages that are sensitive to water stress; and a review of tools for irrigation scheduling. An overview of different methods to deliver water to the field is also provided.
Irrigation water, if managed wisely, is an important tool to optimize productivity of the land and to ensure that no other inputs go to waste. Thus, it is an important tool that can be used in developing a sustainable crop management strategy. Granted, there is great competition from urban and industrial water users, even in the water-rich Mid-South and Southeast, but it is the authors’ hope that by using the knowledge presented here every drop of water applied to cotton will be used beneficially.
Irrigation protects the crop’s yield potential – being short an inch of water at the wrong time can easily result in the loss of 75 pounds of seed and 50 pounds of fiber.
Investments in irrigation scheduling will optimize water use and yield. Over-application of water wastes energy – about a gallon of diesel is required for every acre-inch of water applied per 100 feet of lift.
Early irrigation can improve stand establishment. Ending the irrigation season too early can reduce yield, but extending it too long can increase pest management cost and delay harvest.
Water requirements for cotton vary during the season. At mid-season, cotton water demands are the highest – about 0.28 inch per day.
The sensitivity of cotton to water stress varies by growth stage. First square to first bloom is a critical time for avoiding severe water-deficit stress.
There are a number of sensor systems now available that provide valuable information on when a field is ready to be irrigated.
There are many freely available irrigation scheduling tools that predict when to irrigate based on weather and crop conditions. Often these tools are linked to live weather data.
In general, irrigated fields require more intensive management, not only due to the need to schedule irrigation, but also due to the ability to manage water stress in the field.
There are several options for delivering irrigation water. The three major categories of irrigation systems are: Sprinkler irrigation systems, Surface irrigation, and Drip irrigation.
Additional references and resources related to cotton field irrigation.